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Characterization of Physicochemical Properties, Phosphorus (P) Fractions and P Release of the Everglades Agricultural Ar...

Permanent Link: http://ufdc.ufl.edu/UFE0042440/00001

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Title: Characterization of Physicochemical Properties, Phosphorus (P) Fractions and P Release of the Everglades Agricultural Area (EAA) Canal Sediments
Physical Description: 1 online resource (210 p.)
Language: english
Creator: Das, Jaya
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: Soil and Water Science -- Dissertations, Academic -- UF
Genre: Soil and Water Science thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: CHARACTERIZATION OF PHYSICOCHEMICAL PROPERTIES, PHOSPHORUS (P) FRACTIONS AND P RELEASE OF THE EVERGLADES AGRICULTURAL AREA (EAA) CANAL SEDIMENTS Nutrient enrichment from the EAA particularly P is thought to be responsible for the ecosystem changes in the Everglades. Reduction of P loads from the EAA farms through the implementation of Best Management Practices (BMP) have been going on since 1995. Nevertheless years of P loading the EAA canal sediments portends that the sediments can act as P sources affecting water quality in downstream ecosystems for years to come. Sediment physicochemical properties of the EAA farm and main canals were analyzed. The pH of the canal sediments varied from 7.1 to 8.0 and organic matter content ranged from 20 to 70%. Phosphorus fractionation indicated that the majority of P compounds in the sediments exist as Ca and Mg P, which is generally regarded as stable, but that can be released P over time. Unlike the sediments from the downstream ecosystems organic P content was insignificant and comprised about 6-13% of total P. Phosphorus release from Miami canal was greater than both WPB and Ocean canal. Equilibrium Phosphorus Concentration (EPC) measurements were used to identify sediments either as P sources or sinks. Higher P release from Miami canal sediments resulted in higher EPC values compared to WPB and Ocean canal. The EPC values of Miami canal ranged from 0.07 to 0.15 mg L-1, WPB canal 0.02 to 0.05 mg L-1 and Ocean canal from 0.03 to 0.08 mg L-1. Comparing the EPCw values with the canal water column SRP concentrations, it was concluded that portions of Miami canal and Ocean canal were functioning as a P source. Thus the EAA main canals are the new P sources in addition to the established P sources to the Everglades including the agricultural farms, water from lake Okeechobee. Attempts to reduce P concentrations in the main canals by management of the farm canals can be compensated by P release from the main canal themselves. Thus maintenance and management of the main canals in at least the portions that were found functioning as P source is critical in order to reduce P loads to the Everglades.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jaya Das.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Daroub, Samira H.
Local: Co-adviser: O'Connor, George A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042440:00001

Permanent Link: http://ufdc.ufl.edu/UFE0042440/00001

Material Information

Title: Characterization of Physicochemical Properties, Phosphorus (P) Fractions and P Release of the Everglades Agricultural Area (EAA) Canal Sediments
Physical Description: 1 online resource (210 p.)
Language: english
Creator: Das, Jaya
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: Soil and Water Science -- Dissertations, Academic -- UF
Genre: Soil and Water Science thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: CHARACTERIZATION OF PHYSICOCHEMICAL PROPERTIES, PHOSPHORUS (P) FRACTIONS AND P RELEASE OF THE EVERGLADES AGRICULTURAL AREA (EAA) CANAL SEDIMENTS Nutrient enrichment from the EAA particularly P is thought to be responsible for the ecosystem changes in the Everglades. Reduction of P loads from the EAA farms through the implementation of Best Management Practices (BMP) have been going on since 1995. Nevertheless years of P loading the EAA canal sediments portends that the sediments can act as P sources affecting water quality in downstream ecosystems for years to come. Sediment physicochemical properties of the EAA farm and main canals were analyzed. The pH of the canal sediments varied from 7.1 to 8.0 and organic matter content ranged from 20 to 70%. Phosphorus fractionation indicated that the majority of P compounds in the sediments exist as Ca and Mg P, which is generally regarded as stable, but that can be released P over time. Unlike the sediments from the downstream ecosystems organic P content was insignificant and comprised about 6-13% of total P. Phosphorus release from Miami canal was greater than both WPB and Ocean canal. Equilibrium Phosphorus Concentration (EPC) measurements were used to identify sediments either as P sources or sinks. Higher P release from Miami canal sediments resulted in higher EPC values compared to WPB and Ocean canal. The EPC values of Miami canal ranged from 0.07 to 0.15 mg L-1, WPB canal 0.02 to 0.05 mg L-1 and Ocean canal from 0.03 to 0.08 mg L-1. Comparing the EPCw values with the canal water column SRP concentrations, it was concluded that portions of Miami canal and Ocean canal were functioning as a P source. Thus the EAA main canals are the new P sources in addition to the established P sources to the Everglades including the agricultural farms, water from lake Okeechobee. Attempts to reduce P concentrations in the main canals by management of the farm canals can be compensated by P release from the main canal themselves. Thus maintenance and management of the main canals in at least the portions that were found functioning as P source is critical in order to reduce P loads to the Everglades.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jaya Das.
Thesis: Thesis (Ph.D.)--University of Florida, 2010.
Local: Adviser: Daroub, Samira H.
Local: Co-adviser: O'Connor, George A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0042440:00001


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1 CHARACTERIZATION OF PHYSICOCHEMICAL PROPERTIES, PHOSPHORUS (P) FRACTIONS AND P RELEASE OF THE EVERGLADES AGRICULTURAL AREA (EAA) CANAL SEDIMENTS By JAYA DAS A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010

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2 2010 Jaya Das

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3 To my parents

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4 ACKNOWLEDGMENTS Writing this dissertation has been one of the most challenging tasks I have faced Completing this dissertation has been possible only through the contribution of a large group of people to whom I owe my deepest gratitude, including my parents, friends and my faith in God It is with their support, patienc e and guidance I could complete my study. It is my honor to express my gratitude to my advisor Dr. Samira Daroub who guided and encouraged me through all the challenges of completing my dissertation. I want to thank her for the continued support and encour agement even during hard times as my teacher and mentor. She has taught me more than I could ever give her credit for here. I would also like to t hank my co advisor Dr. George OC onnor, whose sense of discipline and dedication to work inspired me. I also thank other members of my committee, Dr. Willie Harris, Dr. Ion Ghiviriga and Dr. Patrick Inglett and for their guidance and valuable comments. I would like to thank Dr. Reddy for coming to my defense and for his invaluable suggestions on my dissertation. I would like to thank Dr. Orlando Diaz, Dr. Timothy Lang, Dr. Manohardeep Josan, Dr. Olawale Ooladeji and Dr. Jehangir Bhadha who have all helped me at different stages of my research including collecting sediment samples and being there for any of my random questions that I could just drop by and ask. I also thank Ms. Viviana Nadal and Ms. Irina Ognevich for their help and support in lab. Acknowledgements go out to the Everglades Research and Education Center, Belle Glade, for providing the facilities to c onduct this research.

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5 I want to thank my friends Alpana, Thais, Mohua, Pauric, Ann, Chay, Manmeet, Gaurav, Joan Rani, Gwen, Alejandra, Sebastian, Eva Maria and Francisca who have been a source of inspiration and support to me at all times My sincere thanks to all at the Belle Glade center. I would also like to thank Mike Sisk of student services, S oil and Water Science for all the help with my paperwork. I am indebted to my parents, whose love and guidance have always been with me. They are my ultimate role models who taught me to keep my duties above everything in life. I would also like to thank my loving little sister Sweety who misses me a lot but at the same time encourages me to work hard.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES .......................................................................................................... 10 LIST OF FIGURES ........................................................................................................ 13 ABSTRACT ................................................................................................................... 16 CHAPTER 1 INTRODUCTION A ND LITERATURE REVIEW ..................................................... 18 1.1 Role of Sediments in Eutrophication ................................................................. 18 1.1.1 Phosphorus Cycling in Marine Sediments ............................................. 18 1.1.2 Phosphorus Cycling in Stream and Lake Sediments ............................. 20 1.1.3 Phosphorus Cycling in Estuarine Sediment s ......................................... 23 1.2 Everglades Agricultural Area (EAA) .................................................................. 23 1.2.1 Farming and Water Management in EAA .............................................. 24 1.2.2 Drainage and Concern about Nutrients ................................................. 24 1.2.3 Best Management Practices (BMPs) and Restoration .......................... 26 1.2.4 Particulate P in EAA Drainage ............................................................... 27 1.3 Physicochemical Properties and P Fractions of EAA Canals ............................ 28 1.3.1 pH .......................................................................................................... 28 1.3.2 Organic Matter ....................................................................................... 29 1.3.3 Bulk Density .......................................................................................... 29 1.3.4 Phosphorus Fractions ........................................................................... 30 1.4 Nu trient P and Internal Loading ........................................................................ 31 1.4.1 Internal P Loading ................................................................................. 31 1.4.2 Equilibrium Phosphorus Concentration (EPC) ...................................... 32 1.4.3 Mineral Solubility and Internal P Loading .............................................. 33 1.4.4 Organic P and Internal P loading ........................................................... 33 1.5 Research Objectives ......................................................................................... 34 1.6 Dissertation Format ........................................................................................... 35 2 PHYSICOCHEMICAL CHARACTERISTICS AND PHOSPHORUS FRACTIONS OF THE EVERGLADES AGRICULTURAL AREA (EAA) FARM CANAL SEDIMENTS. .......................................................................................................... 38 2.1 Introduction ....................................................................................................... 38 2.1.1 Historical Background ........................................................................... 38 2.1.2 Phosphorus in the EAA ......................................................................... 40 2.1.3 Phosphorus Fractionation ..................................................................... 42 2.2 Material and Methods ....................................................................................... 44 2.2.1 Site Description and Sample Collection ................................................ 44

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7 2.2.2 Sediment Analyses ................................................................................ 47 2.2.3 Statistical Data Analysis ........................................................................ 49 2.3 Results and Discussion ..................................................................................... 50 2.3.1 Physicochemical Properties .................................................................. 50 2.3.2 Phosphorus Fractions of EAA Farm Canals .......................................... 53 2.4 Conclusions ...................................................................................................... 58 3 PHYSICOCHEMICA L CHARACTERISTICS AND PHOSPHORUS FRACTIONATION OF THE EVERGLADES AGRICULTURAL AREA (EAA) MAIN CANAL SEDIMENTS .................................................................................... 69 3.1 Introduction ....................................................................................................... 69 3.1.1 Historical Background. .......................................................................... 69 3.1.2 Factors Affecting Sediment Properties in EAA ...................................... 71 3.2 Materials and Methods ...................................................................................... 73 3.2.1 Description of Main Canals ................................................................... 73 3.2.2 Sediment Sampling ............................................................................... 75 3.2.3 Sediment Analysis ................................................................................. 75 3.2.3.1 Physicochemical properties ..................................................... 75 3.2.3.2 Phosphorus fractions ............................................................... 76 3.2.3.3 Thermogravimetry ................................................................... 76 3.2.3.4 X ray diffraction (XRD) ............................................................ 77 3.2.3.5 31P NMR .................................................................................. 78 3.2.4 Statistical Data Analysis ........................................................................ 78 3.3 Results and Discussion ..................................................................................... 79 3.3.1 Physicochemical Properties .................................................................. 79 3.3.2 Phosphorus Fractions of EAA Main Canal Sediments .......................... 81 3.3.3 Thermogravimetry and X Ray Diffraction .............................................. 82 3.3.4 31P NMR Analysis .................................................................................. 86 3.4 Conclusions ...................................................................................................... 87 4 PHOSPHORUS RELEASE FROM THE MAIN CANAL SEDIMENTS OF THE EVERGLADES AGRICULTURAL AREA (EAA) .................................................... 101 4.1 Introduction ..................................................................................................... 101 4.1.1 Influence of Redox on P Release ........................................................ 101 4.1.2 Influence of Sediment pH on P release ............................................... 102 4.1.3 Phosphorus Flux from Sediments ....................................................... 102 4.1.4 Influence of Organic Matter on P release ............................................ 103 4.1.5 Other Factors Influencing P Release ................................................... 104 4.2 Materials and Methods .................................................................................... 107 4.2.1 Study Site Description ......................................................................... 107 4.2.2 Sediment Sampling ............................................................................. 107 4.2.3 Sediment Core Incubation ................................................................... 108 4.2.3.1 Collection of water samples ................................................... 108 4.2.3.2 Estimation of P flux ................................................................ 109 4.2.4 Sediment Analysis ............................................................................... 110

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8 4.2.4.1 Sediment physicochemical properties ................................... 111 4.2.4.2 Phosphorus fractionation ....................................................... 111 4.2.4.3 Extractable Fe and Al ............................................................ 111 4.2.4.4 Extractable Ca and Mg .......................................................... 111 4.2.5 Statistical Analysis ............................................................................... 111 4.3 Results and Discussion ................................................................................... 112 4.3. 1 Phosphorus Release from Canal Sediments ....................................... 112 4.3.1.1 Miami canal ........................................................................... 112 4.3.1.2 West Palm Beach canal ......................................................... 113 4.3.1.3 Ocean canal .......................................................................... 114 4.3.2 Sediment Physicochemical Properties ................................................ 114 4.3.3 Sediment P Fractions .......................................................................... 114 4.3.4 Extractable Fe, Al, Ca and Mg ............................................................. 114 4.3.5 Factors Affecting P Release ................................................................ 115 4.4 Conclusions .................................................................................................... 118 5 DETERMINATION OF EQUILIBRIUM PHOSPHORUS CONCENTRATIONS OF EAA MAIN CANALS ....................................................................................... 130 5.1 Introduction ..................................................................................................... 130 5.1.1 Importance of EPC Values .................................................................. 131 5.1.2 Linear Adsorption Isotherms ................................................................ 132 5.1.3 Incubation of Intact Sediment Cores ................................................... 133 5.2 Materials and Methods .................................................................................... 134 5.2.1 Study Site Description ......................................................................... 134 5. 2.2 Collection of Sediment Cores .............................................................. 135 5.2.3 Phosphorus Adsorption Isotherm ........................................................ 135 5.2.4 Sediment Core Incubation ................................................................... 137 5.3 Results and Discussion ................................................................................... 138 5.3. 1 Miami Canal ........................................................................................ 138 5.3.1.1 Batch adsorption isotherm ..................................................... 138 5.3.1.2 Incubation of intact sediment cores ....................................... 138 5.3.1.3 Phosphorus release and EPCw .............................................. 140 5.4.1 WPB Canal .......................................................................................... 140 5.4.1.1 Batch adsorption isotherm ..................................................... 140 5.4.1.2 Incubation of intact sediment cores ....................................... 141 5.4.1.3 Phosphorus release and EPCw .............................................. 142 5.5.1 Ocean Canal ....................................................................................... 142 5.5.1.1 Batch adsorption isotherm ..................................................... 142 5.5.1.2 Incubation of intact sediment cores ....................................... 143 5.5.1.3 Phosphorus release and EPCw .............................................. 143 5.6.1 EPC0, EPCw, k, Smax and Sediment Properties .................................... 144 5.4 Conclusions .................................................................................................... 144 6 SUMMARY AND CONCLUSIONS ........................................................................ 159 6.1 Total Phosphorus Storage in Farm Canals ..................................................... 159

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9 6.2 Total Phosphorus Storage in Main Canals ...................................................... 160 6.3 Phosphorus Fractions ..................................................................................... 161 6.4 Phosphorus Release from EAA Main Canals ................................................. 162 6.5 Internal P loading from EAA Main Canal Sediments ....................................... 164 6.6 Equilibrium Phosphorus Concentrations ......................................................... 165 6.7 Conclusions .................................................................................................... 166 APPENDIX A INORGANIC P FRACTIONATION ........................................................................ 175 B EXTRACTABLE Fe AND Al .................................................................................. 178 C EXTRACTABLE Ca AND Mg ................................................................................ 179 D ESTIMATION OF AREA AND VOLUME OF EAA CANALS ................................. 179 E FIGU RES .............................................................................................................. 180 F LATITUDE AND LONGITUTE OF EAA FARM AND MAIN CANALS ................... 184 G ESTIMATION OF ANNUAL INTERNAL P LOADING RATES FROM EAA MAIN CANALS ............................................................................................................... 186 LIST OF REFERENCES ............................................................................................. 189 BIOGRAPHICAL SKETCH .......................................................................................... 210

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10 LIST OF TABLES Table page 2 1 Total P and bulk density values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depths 0 5 cm and 510 cm. ...................... 61 2 2 Percent LOI and pH values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depths 05 cm and 5 10 cm. ................................... 62 2 3 Mean total P, bulk density(BD), %LOI and pH values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depths 05 cm and 510 cm. ...................................................................................................................... 62 2 4 Mean total P, bulk density(BD), %LOI and pH values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depth 05 cm and 5 10 cm depth. ............................................................................................................ 63 2 5 KClP, NaOH Pi and NaOH Po fractions of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) at depths 05 cm and 510 cm. ................ 66 2 6 KClP, NaOH Pi, NaOHPo, of farm canals 00A, 09A and 06AB from transect 1(T1 ) to transect 5(T5) at depths 05 cm and 5 10 cm. ...................................... 67 2 7 Mean HCl P and ResidueP of farm canals 00A, 09A and 06AB from transect 1( T1) to transect 5(T5) at depths 05 cm and 5 10 cm. ...................................... 67 2 8 HClP and ResidueP of farm canals 00A, 09A and 06AB from transect1(T1) to transect 5(T5) at depths 05 cm and 510 cm. ................................................ 68 2 9 Correlation between sediment BD, %LOI, pH and Total P. ................................ 68 3 1 Mean total P and bulk density of Miami, WPB and Ocean canal sediments from T1 to T4. ..................................................................................................... 90 3 2 Mean total P and bulk density (BD) of Miami, WPB and Ocean canal sediments. .......................................................................................................... 91 3 3 Mean %LOI and pH values of Miami, WPB and Ocean canal sediments from T1 to T4. ............................................................................................................. 91 3 4 Mean %LOI and pH of Miami, WPB and Ocean canal sediments. ..................... 92 3 5 Mean labile P, NaOH Pi and NaOH Po fractions of Miami, WPB and Ocean canal sediments from T1 to T4. .......................................................................... 95 3 6 Mean KCl P, NaOH Pi and NaOH Po of Miami, WPB and Ocean canal sediments. .......................................................................................................... 96

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11 3 7 Mean HCl P and Residue P fractions of Miami, WPB and Ocean canal from T1 to T4. ............................................................................................................. 96 3 8 Mean HCl P and ResidueP of Miami, WPB and Ocean canal sediments. ........ 97 3 9 Minerals identified in sediments of Miami canal sediments from T1 to T4. ......... 98 3 10 Minerals identified in sediments of WPB canal sediments from T1 to T4. .......... 99 3 11 Minerals identified in sediments of Miami, WPB and Ocean canal sediments from T1 to T4. ................................................................................................... 100 4 1 Ammonium oxalate extractable Fe, Al, and acetic acid extractable Ca, Mg from Miami, WPB and Ocean canal sediments. ............................................... 127 4 2 Correlation of total P released from canal sediments over exchange 1, 2 and 3 with sediment physicochemical properties BD, %LOI, pH, Fe, Al, Ca and Mg. ................................................................................................................... 127 4 3 Correlation of total P released from canal sediments over exchange 1, 2 and 3 with total P and sediment P fractions. ............................................................ 127 5 1 Equilibrium Phosphorus Concentrations (EPC0) from adsorption isotherms, maximum sorption capacity (Smax) and intensity of adsorption (k) for Miami canal T1, T2, T3 and T4 sediments. ................................................................. 146 5 2 Equilibrium Phosphorus Concentrations (EPCw) from sediment column incubation study for Miami canal T1, T2, T3 and T4 sediments. ....................... 148 5 3 Equilibrium Phosphorus Concentrations (EPC0) from adsorption isotherms, maximum sorption capac ity (Smax) and intensity of adsorption (k) for WPB canal T1, T2, T3 and T4 sediments. ................................................................. 150 5 4 Equilibrium Phosphorus Concentrations (EPCw) from sediment column incubation study for WPB canal T1, T2, T3 and T4 sediments. ........................ 152 5 5 Equilibrium Phosphorus Concentrations (EPC0) from adsorption isotherms, maximum sorption capacity (Smax) and intensity of adsorption (k) for Ocean canal T1, T2, T3 and T4 sediments. ................................................................. 154 5 6 Equilibrium Phosphorus Concentrations (EPCw) from sediment column incubation study for Ocean canal T1, T2, T3 and T4 sediments. ...................... 156 5 7 Correlation between sediment metal (Fe, Al, Ca and Mg) and EPC0, EPCw, k and Smax. ........................................................................................................... 158 5 8 Correlation between sediment physicochemical properties with EPC0 and EPCw. ............................................................................................................... 158

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12 5 9 Correlation between sediment EPC0 and EPCw with sediment P fractions, total P and P released from intact sediment study. ........................................... 158 6 1 Estimation of total P storage in EAA main (Miami, WPB, Ocean) and farm (09A, 00A, 06AB) canal sediments. .................................................................. 168 6 2 Estimation of annual internal P loading from Miami canal exchanges 1, 2 and 3. ...................................................................................................................... 172 6 3 Estimation of annual internal P loading from WPB canal exchanges 1, 2 and 3. ...................................................................................................................... 172 6 4 Estimation of annual internal P loading from Ocean canal sediments during exchanges 1, 2 and 3. ...................................................................................... 173 6 5 Estimation of annual internal P loading from Miami, WPB and Ocean canal sediments over exchange 1, 2 and 3. ............................................................... 173 6 6 Comparison of EPCw and SRP concentrations of Miami, WPB and Ocean canal sediments. ............................................................................................... 174 F 1 Latitude and longitude values of farm canal 09A transects. ............................. 184 F 2 Latitude and longitude of farm canal 00A transects .......................................... 184 F 3 Latitude and longitude of farm canal 06AB transects ....................................... 184 G 1 Estimation annual internal P loading from Miami canal exchange 1. ................ 186 G 2 Estimation annual internal P loading from Miami canal exchange 2. ................ 186 G 3 Estimation annual internal P loading from Miami canal exchange 3. ................ 186 G 4 Estimation annual internal P loading from WPB canal exchange 1. ................. 187 G 5 Estimation annual internal P loading from WPB canal exchange 2. ................. 187 G 6 Estimation annual internal P loading from WPB canal exchange 3. ................. 187 G 7 Estimation annual internal P loading from Ocean canal exchange 1. ............... 188 G 8 Estimation annual internal P loading from Ocean canal exchange 2. ............... 188 G 9 Estimation annual internal P loading from Ocean canal exchange 3. ............... 188

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13 LIST OF FIGURES Figure page 1 1 Flowchart of the different experimental steps performed upon the EAA farm canal sediments. ................................................................................................. 36 1 2 Flowchart of the different experimental steps performed upon the EAA main canal sediments. ................................................................................................. 37 2 1 Farm basins and positions of farm canals 00A, 09A and 06AB in EAA. ............. 61 2 2 Percent comparison of KCl P, NaOH Pi, NaOHPo, HClP and Residue P fractions at five transects (T1T5) at depth 05 cm in farm canal 00A, 09A and 06AB. ........................................................................................................... 64 2 3 Percent comparison of KCl P, NaOH Pi, NaOHPo, HClP and Residue P fractions at five transects (T1T5) at depth 510 cm in farm canal 00A, 09A and 06AB. ........................................................................................................... 65 3 1 Different bedrock layers underlying EAA soils (USGS maps). ............................ 89 3 2 Position of EAA main canals and the sampling transects within the main canals. ................................................................................................................ 90 3 3 Percent comparison of different P fractions from T1 to T4 in Miami, WPB and Ocean canal at depth 05 cm. ............................................................................. 93 3 4 Percent comparison of different P fractions from T1 to T4 in Miami, WPB and Ocean canal at depth 510 cm. ........................................................................... 94 3 5 Weight loss due to OM, Dolomite and Calcite of Miami, WPB and Ocean canal sediments from T1 to T4. .......................................................................... 97 3 6 X ray diffraction patterns from Miami canal sediments from T1 to T4. ................ 98 3 7 X ray diffraction patterns from WPB canal sediments T1 to T4. ......................... 99 3 8 X ray diffraction patterns from Ocean canal sediments T1 to T4. ..................... 100 4 1 Transect locations T1 to T4 of Miami canal, WPB canal and Ocean canal in Everglades Agricultural Area. ........................................................................... 120 4 2 Phosphorus release from Miami canal sediments T1T4 and exchange 1, 2 and 3. ............................................................................................................... 121 4 3 Total P released from Miami canal sediments over exchange 1, 2 and 3. ........ 122

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14 4 4 Phosphorus flux from Miami canal sediments T1T4 and exchange 1, 2 and 3. ...................................................................................................................... 122 4 5 Phos phorus release from WPB canal sediments T1T4 and exchange 1, 2 and 3. ............................................................................................................... 123 4 6 Total P released from WPB canal sediments over exchange 1, 2 and 3. ......... 124 4 7 Phosphorus flux from WPB canal sediments T1T4 and exchange 1, 2 and 3. 124 4 8 Phosphorus release from Ocean canal sediments T1T4 and exchange 1, 2 and 3. ............................................................................................................... 125 4 9 Total P released from Ocean canal sediments over exchange 1, 2 and 3. ....... 126 4 10 Phosphorus flux from Ocean canal sediments T1T4 and exchange 1, 2 and 3. ...................................................................................................................... 126 4 11 Correlation between water column total P and SRP from sediment incubation study. ................................................................................................................ 128 4 12 Sediment surface layer of sediment core from Ocean canal. ........................... 128 4 13 Sediment surface layer of sediment core from WPB canal. .............................. 128 4 14 Sediments from WPB canal. ............................................................................. 129 4 15 Sediment cores from WPB canal showing layers of CaCO3. ............................ 129 5 1 Determination of EPC0 from linear adsorption isotherm for Miami canal, T1. ... 146 5 2 Cumulative P release from Miami canal T1T4 sediments during exchanges 1 5. ................................................................................................................... 147 5 3 Determination of EPCw of Miami canal T1 from sediment core incubation study. ................................................................................................................ 148 5 4 Total P released and retained from Miami canal T1T4 sediments during exchanges 15. ................................................................................................. 149 5 5 Determination of EPC0 from linear adsorption isotherm for WPB canal T1. ..... 150 5 6 Cumulative P release from WPB canal T1T4 sediments during exchanges 15. ...................................................................................................................... 151 5 7 Determination of EPCw for WPB canal T1 from sediment core incubation study. ................................................................................................................ 152

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15 5 8 Total P released and retained from WPB canal T1T4 sediments during exchanges 15. ................................................................................................. 153 5 9 Determination of EPC0 from linear adsorption isotherm for Ocean canal T1. ... 154 5 10 Cumulative P re lease from Ocean canal T1T4 sediments during exchanges 1 5. ................................................................................................................... 155 5 11 Determination of EPCw for Ocean canal T1 from sediment core i ncubation study. ................................................................................................................ 156 5 12 Total P released and retained from Ocean canal T1T4 sediments during exchanges 15. ................................................................................................. 157 6 1 Schematic representation of P release from a section of Miami canal sediments ......................................................................................................... 169 6 2 Schematic representation of P release from a section of WPB canal sediments ......................................................................................................... 170 6 3 Schematic representation of P release from a section of Ocean canal sediments ......................................................................................................... 171 6 4 Water and nutrient flow through the Everglades system. ................................. 174 E 1 Inorganic P fractionation scheme. .................................................................... 180 E 2 Map of farm canal 09A .................................................................................... 180 E 3 Map of farm canal 00A. .................................................................................... 181 E 4 Map of farm canal 06AB. .................................................................................. 181

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16 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CHARACTERIZATION OF PHYSICOCHEMICAL PROPERTIES, PHOSPHORUS (P) FRACTIONS AND P RELEASE OF THE EVERGLADES AGRICULTURAL AREA (EAA) CANAL SEDIMENTS By Jaya Das December 2010 Chair: Samira Daroub Cochair: George OConnor Major: Soil and Water Science Nutrient enrichment from the EAA particularly P is thought to be responsible for the ecosystem changes in the Ever glades. Reduction of P loads fro m the EAA farms through the implementation of Best Management Practices (BMP) have been going on since 1995. Nevertheless years of P loading the EAA canal sediments portends that the sediments can act as P sourc e s affecting water quality in downstream ecosystems for years to come. Sediment physicochemical properties of the EAA farm and main canals were analyzed. The pH of the canal sediments varied from 7.1 to 8.0 and organic matter content ranged from 20 to 70%. Phosphorus fractionation indicated that the majority of P compounds in the sediments exist as Ca and Mg P which is generally regarded as stable, but that can be released P over time. Unlike the sediments from the downstream ecosystems organic P content was insignificant and comprised about 613% of total P Phosphorus release from Miami canal was greater than both WPB and Ocean canal. Equilibrium Phosphorus Concentration (EPC) measure ments were used to identify sediments either as P sources or sinks. Higher P release from Miami canal sediments

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17 resulted in higher EPC values compared to WPB and Ocean canal. The EPC values of Miami canal ranged from 0.07 to 0.15 mg L1, WPB canal 0.02 to 0.05 mg L1 and Ocean canal from 0.03 to 0.08 mg L1. Comparing the EPCw values with the canal water column SRP concentrations it was concluded that portions of Miami canal and Ocean canal were functioning as a P source. Thus the EAA main canals are the new P sources in addition to the established P sources to the Everglades including the agricultural farms, water from lake Okeechobee. Attempts to reduce P concentrations in the main canals by management of the farm canals can be compensated by P release fr om the main canal themselves. Thus maintenance and management of the main canals in at least the portions that were found functioning as P source is critical in order to reduce P loads to the Everglades.

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18 CHAPTER 1 INTRODUCTION AND LIT ERATURE REVIEW 1.1 Role of Sediments in Eutrophication P hosphorus (P) releases from sediments including sea (Smith, 1984) streams and lakes (Mortimer, 1941, 1942; Holdren and Armstrong 1980) can result in nutrient enrichment and is considered an important control for the productivities of these water bodies Studies on lake sediments in the Netherlends, Lijklema (1980) observed that depending upon hydraulic detention time about 50% to 100% of the total P load can accumulate in t he sediments This accumulated P can cause P release through internal loading and can lead to eutrophication of lakes through increased primary productivity ( Lijklema 1980) The flux of P in these water bodies play a key role in regulating the P concentration in the water column ( Filippelli and Delaney, 1992, 1994) thus, understanding the processes that cause P release or P accumulation in sediments is crucial to comprehend P cycling and possible control mechanisms in these water bodies. 1.1.1 Phosphorus Cycling in Marine Sediments Studies by Ingall and Jahnke (1994) have indicated that sedimentation of P in marine sedi ments are affected by the water oxygen concentrations and the sedimentation efficiency of oxygen depleted waters is lower than oxygen rich waters. Lower oxygen concentrations are also thought to be important in controlling the accumulation of organic matter in marine sediments (Thiede and van Andel, 1977). The r easons for the development of anoxic conditions and the resultant accumulation of organic matter in bottom waters of marine environ ments are thought to be due to reduced circulat ion of oxygen in deep waters accompanied by high productivity and

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19 respiratory oxygen consump tion (Herbert and Sarmiento, 1991). Organic matter oxidation and resultant P release in marine sediments can occur through a sequence of different pathways in the order of decreasing free energy yield per mole of carbon oxidized, that occurs sequentially t hrough oxic respiration, denitrification, metal oxide reduction, sulfate reduction and methanogenesis respectively (Froelich et al., 1979). The actual scenario is much more complex since the reactants participating in organic matter decomposition take part simultaneously in other reactions as well. The composition of organic matter is also thought to influence P flux in marine sediments. Studies by Likens et al. ( 1981) showed that the C/P ratio s of marine planktonic organic matter is around 106 whereas terr estrial organic matter has a ratio of 800 to 2050, which suggests that organic matter decomposition in sites containing a high proportion of marine planktonic material would yield higher P flux compared to terrestrial organic matter. Higher P flux from anoxic marine, lake or estuarine sediments relative to oxic sediments, can also result from the reduction and simultaneous P release from iron oxides due to high P sorption capacity of these oxides for phosphates (Lucotte and dAnglejan, 1988; Buffle et al., 1989). Increased P flux due to reduction of iron oxides are more likely to occur at sites with low oxygen concentrations (Ingal and Jahnke, 1997). It is suggested that in sediments with oxic waters, oxic conditions can develop in the top few centimeters of the sediments that can prevent P release by oxidative precipitation of the iron oxides (Froelich et al., 1988). However, it is considered highly unlikely that the oxic layer will completely prevent P flux, rather it is thought that a steady state condition develops where the quantity of P precipita ted is a function of the concentration of oxidized and reduced iron (Ingall and Jahnke, 1997). Working with lake

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20 sediments Mortimer (1942, 1942) demonstrated the presence of an oxic microzone at the sediment water interface that inhibited P release from sediment layers below. Anoxic conditions in the overlying water however were shown to stimulate P release (Mortimer, 1941, 1942). Studies on bacteria and protozoa have shown that, they can store utilize and release P that is dependent on redox conditions (Van Veen et al., 1993). Thus redox fluctuations can also cause P release from sediment bacterial communities. For example, Acinetobacter spp immobilizes or stores P under aerobic conditions and in oxygen depleted conditions uses the stored P as energy source that is subsequently released as dissolved P (Van Veen et al., 1993). During immobilization o f dissolved P by bacteria, a fraction of the assimilated P can also be stored as recalcitrant organic P compounds In marine environments, high fluoride concentrations can cause the precipitation of calcium phosphate phases like carbonate fluorapatite (Rut tenberg and Berner, 1993). 1.1.2 Phosphorus Cycling in Stream and Lake Sediments Similar to marine sediments, researchers have suggested three important mechanisms for P release from lake sediments that are: P release from sediments under anoxic conditions ( Mortimer, 1941, 1942; Holdren and Armstrong 1980); resuspension of sediments (Reynoldson and Hamilton, 1982) and release of dissolved and particulate P from macrophytes (Landers 1982). Increased P release under anoxic conditions have been studied in several lake sediments including mud sediments of Denmark (Kamp Nielsen 1974), estuarine sediments ( Khalid et al., 1978) and near shore/littoral sediments (Bostrom and Pettersson, 1982). In spite of the fact that anoxic conditions encourage P release, sediments i n aerated waters have been shown to substantially release P ( Ryding and Forsberg

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21 1977; Stevens and Gibson, 1977). It has been demonstrated that redox values can decrease to around 200 mV ( Sediment resuspension in lake Arreso, Denmark, caused 2030 times greater P release than undisturbed lake sediment (Sondergaard et al., 1992) and about 810 times greater P release in lake Taihu, China, (Fan et al., 2001) Interestingly enough bioturbation and resuspension of sediments was found to cause high P flux in calcareous lake Vombsjon, Sweden but inconsequential P rel e ases from noncalcar eous lakes Trummen, Sweden and l ake Arungen, Norway (Graneli 1979) Bostrom et al., 1982) at a depth of 1 cm in sediments under aerobic water column. The P release due to mineralization of organic matter, (Lee et al. 1977), high sediment pH and increasing temperature (MollerAndersen, 1974) are considered important factors in affecting P flux from sediments in aerobic waters. Increased bacterial activities in sediment interface with aerobic water at high temperatures can create an anoxic microzone (Kam p Nielsen 1974 ; Holdren and Armstrong 1980; Bostrom and Pettersson, 1982). Phosphorus release from such temporary or short ti me anoxic sediments can be affected by all the processes as in anoxic sediments (Kamp Nielsen 1974; Holdren and Armstrong 1980). Increased temperature and resultant increased rates on microbial oxygen consumption in sediments have been universally shown to increase P release, ( Holdren and Armstrong 1980; Kelderman, 1984) although Holdren and Armstrong (1980) found that temperature increase had inconsequential effect on P release from non calcareous Wisconsin lakes. In contrast, it was found that increase d temperature caused considerable P release from calcareous lake Wisconsin sediments ( Holdren and Armstrong 1980) and lak e Vallentunasjon, Sweden ( Bostr om and Pettersson 1982 ).

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22 Sediment pH, presence of nitrates, diel variations, seasonal variations, temperature, bioturbation, microbial activity and presence of macrophytes, are other factors identified as factors affecting P release from lake sediments (Bostrom et al. 1982). Nitrate concentrations and pH have been shown to both increase and decrease P release (Andersen 1982; Bostrom and Petterss on, 1982; Tiren and Pettersson, 1985). The presence of macrophytes and microalgae can considerably influence P flux by photosynthesis and respiration (Carlton and Wetzel 1987) Photosynthesis of macrophytes and microalgae at low light intensities of as much as <50 mol quanta m2 s1 have been found to be sufficient to affect pH and oxygen concentrations in sediments (Carlton and Wetzel 1987). Using oxygen sensitive microelectrodes, 32PO4 3 In addition to biogeochemical factors, s trati fication of water layers in lakes have been shown to affect P flux (Larsen et al., 1981; Riley and Prepas 1984). The relationship between deepwater accumulations of P with the surface water P concentration is subject to study and research has shown a total P increase of about 1391000% in surface water after P releases from sediments (Larsen et al., 1981). Studies in Nakamun and Halfmoon lakes in Alberta, Canada showed total P increase of 3 43% and 3152% in the surface water compared to deep water (Riley and Prepas radiotracer and a flow through system using sediment cores collected from Lawrence lake, Michigan, Carlton and Weltzel ( 1988) demonstrated that c onsecutive photosynthesis and respiration can result in oxic conditions during day while anoxic conditions at night This diel variation can result in the daily construction and destruction of oxidized microzone in surficial lake sediments (Mortimer 1941, 1942) promoting P releases

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23 1984). The reason of t he increase in total P in surface waters is not very clear but was attributed to mixing of resuspended sediments (Riley and Prepas, 1984). 1.1.3 Phosphorus Cycling in Estuarine Sediments In estuarine environments tidal flooding and ebbing present a dynamic and complex environment that includes tidal currents, sediment resuspension, settling of particulates, daily variation of water depth, which has been s hown to influence P flux (L illebo et al., 2004; Ha kanson and Jansson, 1983) Lillebo et al., 2004 determined P flux in land forms in Mondego estuary, Portugal including seagrass beds, salt marshes, mud and sand flats without vegetation and concluded that P flux from all the estuarine land forms were higher during t he first hours of a tidal flood and lowers at high tide. Lillebo et al., 2004 also showed that P release increased with the combination of shallow depth and enhanced temperature. 1.2 Everglades Agricultural Area (EAA) The original Florida Everglades water shed was a broad, freshwater marsh that extended from what is now the Kissimmee River basin, through l ake Okeechobee to the southern tip of the Florida peninsula. The historic flow, arising from a nearly flat land slope, was at very low velocity from north to south. Historically the Everglades was a contiguous wetland rich in organic soils underlain by marl and limestone The system was characteristically oligotrophic (Davis and Ogden, 1994) and P limited (McCormick et al., 1996). A s a part for the Central and South Florida Project (1953 to 1967) the US Army Corps of Engineers (USCOE) drained and divided the Everglades into the Everglades Agricultural Area (EAA), the Water Conservation Areas (WCA) and the Everglades National Park (ENP) Drainage was accompl ished by the construction of

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24 over 2500 canals, levees and hundreds of water control structures (Chimney and Goforth 2001). 1.2 .1 Farming and Water M anagement in EAA Agricultu re in the Everglades began after drainage development ( 1906 1927) and expanded with the completion of several water control projects in the early 1950s (Snyder and Davidson, 1994). T oday t he EAA c onsists of approximately of 2,872 km2Water management in the EAA is crucial due to the flat topography of the area and uneven rainfall distribution makes drainage compulsory (Bottcher and Izuno, 1994). During the wet season, surp lus rainfall and runoff has to be pumped out of the EAA. During the dry season, irrigation water is supplied primarily from l ake Okeechobee ( SFER 2010a ). of organic soils (SFER 2010a ). The main commercially grown crops in EAA are sugarcane, winter veget ables, rice ( Oryza sativa ) and sod ( Bottcher and Izuno, 1994). 1.2 .2 Drainage and Concern about N utrients The EA A is divided into four agricultural basins S 8/S3, S 7/S2, S 6, and S 5A, each drained by main canals originating from l ake Okeechobee and emptying i nto the Atlantic Ocean. Drainage in EAA is accomplished using pumps and a network of field ditches and canals operated by pumps and gates. Ditches are onfarm waterways that discharge into the farm canals. Farm canals are controlled by privately owned pump stations and are used to irrigate and drain the farms which drain into the main canals. The S 8/S3 basin is drained by the Miami canal the S 7/S2 basin by t he North New River canal the S 6 basin by Hillsboro canal and the S 5A basin drained by West Palm Beach and Ocean canal (Tracey, 2006) ( see Chapter 2, Figure 21 ). Three connecting canals facilitate runoff and supply irrigation water: Bolles canal, Cross c anal, and Ocean

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25 canal (SFER 2010a). The connecting canals do not originate from l ake Okeechobee but connect the main canals. Nutrient rich agricultural drainage water generated in the EAA flow s from the farm canals to the main canals (Stuck et al., 2002). On average, about 1 x 109 m3Agricultural drainage water containing P from the EA A has been linked to several ecosystem changes including reduction in population of wading birds and intrusion of cattails into native sawgrass and slough habitat s (Noe et al., 2001). Responses to P enrichment have been documented in several of the ecosyst em components including surface water (Koch and Reddy, 1992; McCormick et al., 1996), periphytons (Pan et al., 2000), soils (Koch and Reddy, 1992; Craft and Richardson 1993), macrophytes (Doren et al., 1997; Miao and Skl ar, 1998) and consumers (Rader and Richardson, 1994). Efforts to mediate the environmental changes arising from modified flow include restoration efforts focus ed on reducing nutrient loading ( especially P ) and restoring a more natural hydroperiod to sensitive wetland areas (Light and Dineen, 1994). of drainage water is discharged from the EAA annually (SFER, 2010 a ) and flows into the Everglades Protection Area (EPA) (Abtew and Khanal, 1994; Abtew and Obeysekera, 1996). The EPA consists of Arthur R. Marshall Loxahatchee National Wildlife Refuge (Refuge), Water Conservation Areas (WCAs), the Everglades National Park (ENP) and the Storm Water Treatment Areas (STAs) (SFER 2009). The drainage/runoff of the EAA is the main source of surface wat er inflow into the EPA ( SFER 2009). The nutrient enrichment, specifically phosphorus (P), is cited as one of the causes of ecosystem changes in the WCAs and the ENP (LOTAC 1990; Whalen et al., 1992).

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26 1 .2 .3 Best Management Practices (BMPs) and Restoration Remediation plans were dictated by the Everglades Forever Act (EFA) of 1994 [Section 373.4592, Florida Statutes (F.S.)]. The Restoration Planning and Permitting Program under the EFA is the principal guide in the restoration and protection of the Everglades ecological system. T he Plan for Achieving Long Term Water Quality Goals (Long Term Plan) in EFA include control of P sources by implementation of BMPs for P reduction, ( SFER 2009). Categ ories of BMPs implemented in the EAA to control agricultural drainage water runoff quality include water management, nutrient management and control of particulate matter from farms and canals ( SFER 2002). P ractices include modifying pumping practices, pr otecting canal banks with vegetation, minimizing fertilizer application, using cover crops, and retention of on farm drainage ( SFER 2002). The BMP regulatory program requires P loads in drainage water leaving the EAA to be reduced by at least 25% relativ e to the historic levels ( SFER 2009). The Comprehensive Everglades Restoration Plan (CERP) was authorized in 1999 as part of the Federal Water Resources Development Act to protect the ENP. Under CERP, the South Florida Water Management District (SFWMD) co nstructed six large wetlands located between the EAA and WCA, to remove excess P from agricultural drainage water before it is discharged into the WCA canals. The wetlands also called the Storm Treatment Areas or STAs rang e in size from 3500 to 6 700 ha are situated along the SFWMD main canals that treat discharges from the Everglades basins ( Chimney and Goforth 2001).

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27 1.2 .4 Particulate P in EAA D rainage The nature and composition of particulate matter from farms can considerably influence the physical and chemical properties of the EAA canal sediments. The predominantly organic particulate matter is light and flocculent that can be easily transported to downstream ecosystems (SFER 2004; Dierberg and DeBusk 2008) as suspended particles spread throughout the entire water column (Daroub, 2002a). The P content of particulate materials containing a mixture of detrital waterweeds and planktonic growth can range from 15003500 mg kg1 for waterweeds and from 900015000 mg kg1Drainage water from EAA consists of dissolved P and particulate P. The so urce of dissolved P can be fertilizers and mineralized soil organic matter (Daroub et al., 2002a). Izuno and Rice (1999) estimated that particulate P constitutes about 20 to 70% of the total P exported from EAA farms. Particulate P consisting of filamentous algae, plankton, macrophyte particles and soil particles dominate P export of ag ricultural drainage water from the EAA farms (Stuck, 2001). Apart from EAA farms particulate P can also arise from erosion of P enriched canal banks (Andreis, 1993; Hutcheon Engineers, 1995). The biological nature of particulate P and the presence of calc ium carbonate bedrock influence the sediment characteristics. The EAA bedrock formed from precipitated calcium carbonate (CaCO for different planktons The part iculate P can increase P storage in EAA canal sediments and in the P limited downstream ecosystems. 3) (Scott, 1997) can influence sediment properties including pH, mineralogical composition and distribution of different P fractio ns.

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28 1.3 Ph ysicochemical Properties and P F ractions of EAA Canals 1.3 .1 pH Soils and sediments in Everglades have circum neutral pH compared to extremely low pH values found in organic and peat soils. The pH values of sediments in WCA 2A are around 7.2 (DeBusk et al., 1994) and in WCA 3A around 7 (Swift and Nicholas, 1987). The p h values of cultivated soils in EAA, was found to be around 7.3, 7.4 and 6.6 for Dania, Lauderhill and Pahokee soil series respectively (Janardhanan, 2007). Typically rain fed peat lands are low in plant nutrients and have low pH values between 3 and 5.5 (Clymo et al., 1984) but at the same time e xtremely acidic Histosols with pH values around 3, have also been observed in drained coastal region bogs containing pyrite (FeS2Sediment pH values can influence the distribution of different P fractions. Phosphorus in alkaline wetland sediments tend to be preferentially retained as insoluble Ca P or Mg P compounds (Moore and Reddy 1994; Reddy et al., 1 999; Richardson, 1999) whereas Fe and Al phosphate compounds tend to dominate in wetland systems with low pH values (Khalid et al., 1977). ) ( White et al., 1997) Several laborat ory studies have demonstrated increased P flux from sediments to the overlying water column with increasing pH (Andersen, 1975). H igh pH values facilitate P release from sediments by competition between hydroxide (OH-) and phosphate (H2PO4 -) ions for sorption sites on iron (Bostrm, 1984). The proposed release mechanism was supported by a correlation between pH and internal p hosphorus loading (Walker, 2001).

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29 1.3 .2 Organic M atter Farm canals in EAA can retain drainage water for long periods during which plant detritus, algae and macrophyte particles accumulate until they are discharged by pumps to the farm canals (Dierberg and DeBusk, 2008). The accumulation of organic matter in farm canals can influence sediment physical properties as well as quality of the overlying water column. T he light and flocculent nature of organic m atter accumulated in EAA canals leads to surface layer sediments with lower bulk densities than subsurface layers and affect transport properties. During aerobic decomposition of organic matter, P and other elements associated with organic matter along with carbon are mineralized, releasing P (Qualls and Richardson, 2008). Anoxic conditions prevailing in sediments promote fermentation of organic matter, which can also release P (Goltermann, 2001). Organic acids released during fermentation can reduce the interstitial pH dissolve carbonate minerals and rel e ase associated P (Marsden, 1989). The o rganic acids chelat e with calcium, iron, manganese and aluminum thereby promoting P release (Bostrm et al., 1982; Stauffer and Armstrong, 1986) 1.3 .3 Bulk Density Sediments can affect water quality wherever they are transported, and the transport of sediments in EAA is profoundly affected by the pumping rates Rates are easily doubled or tripled by running multiple pumps or by switching from small to large capacity pumps (SFER 2004). Sediment transportability varies with pumping rates, velocity of water in the canals and bulk density of sediments (Lick et al., 2001). Studies in the EAA have shown that lower sediment bulk densities were related to greater transportability (Daroub et al., 2002b). Sediment erosion rates (cm s1) of river

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30 sediments determined by Jepsen et al. ( 1997) in laboratory studies were unique function s of bulk density and decreased as the bulk density increased. Low bulk densities make sediments susceptible to resuspension that can affect water quality. Resuspension of lake sediments in the windexposed l ake Arreso, De nmark, resulted in P loading 2030 times greater than loading from undisturbed lake sediment (Sondergaard et al., 1992 ). S torm events that resuspend sedim ents have the potential to enhance P mobilization by increasing sediment surface for P release, as well as by carrying P mass into the water column from sediments (Laenen and LeTourneau, 1996). 1.3 .4 Phosphorus Fractions The general nature of canal sediments in the EAA has been investigated by measuring total P content in suspended solids of drainage water from EAA farms (Stuck, 1996; Stuck et al., 2001; SFER 2006), but the exact chemical nature of the sediments is not known. The forms in whi ch total P is chemically held is best understood by sequential fractional techniques that extract theoretically discrete forms of P removing one component after another (Graetz and Nair 1995; Reddy et al., 1995). The quantification of the different P fra ctions can be useful in predicting P responses to physicochemical changes and in understanding the internal P cycling (Olila et al., 1994). James et al. (1995) studied sediments of l ake Pepin and showed that P could be released under both oxic and anoxic c onditions Release depended on P forms, and P release rates cor related with the labile and Fe and Al associated P Phosphorus fractionation schemes divide P into inorganic and organic fractions of different solubility and identify the nature and distributi on of the different P fractions including labile and recalcitrant P fractions. Reddy et al. ( 1995, 1998 ) suggested

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31 fractionation schemes consisting of five steps: KCl extractable P (KCl Pi), NaOH extractable P, HCl extractable P (HCl Pi), and residual P ( ResidueP). The KClPi fraction represents labile Pi that is water soluble and exchangeable (loosely adsorbed); NaOH extractable P represents Feand Al bound P (NaOH Pi) and humic and fulvic acids (NaOH Po). The HClPi fraction represent Ca and Mg bound P, and r esidueP represents recalcitrant organic P compounds and P bound to minerals. 1.4 Nutrient P and Internal Loading 1.4 .1 Internal P Loading The ultimate goal of farm BMPs and constructed wetlands is to deliver water of low P concentration to the downstream ecosystems in South Florida. Historic P loading to main canals, and the resulting P flux from accumulated sediments to the water column, i s a potential additional source of P. A reduction in external P load does not alw ays translate in a decrease in t otal P in the water column because high internal sediment P load can initiate and sustain algal blooms and eutrophication (Welch and Cooke, 1995). The quantity of P stored in the sediments is great compared to P in the water column, so even small amou nts of P released from sediments can significantly impact P concentrations in the water column (Bostrm et al., 1982). Internal loading is the recycling of nutrients from bottom sediments to the overlying water column (Carpenter, 1983). After external load reduction, internal loads of sediments determine the trophic status of a water body and the time for recovery (Petterson, 1998). It is suggested that P stored in surface soils in the EAA can sustain a P load of 170 mt per year for 47 to 118 years to the downstream ecosystems (Reddy et al., 2010).

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32 1.4 .2 Equilibrium Phosphorus Concentration (EPC) Equilibrium Phosphorus Concentration (EPC) values can indicate previous loading s to the sediments (Martin, 2004). The extent of internal loading from the sediments can be determined by the EPC (Martin, 2004). The EPC is the P concentration in the water column at which no net flux i.e. release or retention, occurs from the sediments to the water and the P in solution is considered to be in equilibrium with P in the s olid phase (Reddy et al., 1999). The concept of EPC has been used to understand the quantity and direction of soluble reactive phosphorus (SRP) flux in sediments (House and Denison, 2002). At water column SRP concentrations above the EPC, SRP is retained b y the sediments whereas at SRP concentrations below EPC, the sediments serve as source for SRP (Reddy et al., 1995; Pant and Reddy, 2001; Zhou et al., 2005). Agricultural input of P into the canals can increase the EPC values of the sediments and reflect P loading (Reddy et al., 1998). Determination of EPC values in the Everglades have b een conducted in the Kissimmee R iver watershed, l ake Okeechobee sediments, the dairies and farms north of the lake and the Wa ter Conservation Areas. For example, the EPC v alues of stream sediments in Lower Kissimmee River Basin, Florida, was around 0. 0 13 mg P L1 (Martin, 2004) The nutrient impacted wetland soils in Fisheating Creek and Istokpoga Basins had EPC values of 1.95 and 3.9 mg P L1 respectively (Dunne et al., 2005). Clark et al. (2002) noted the wide spatial and temporal variability of internal P loads and P release potential s within the south Florida canals adjacent to the EAA and the Water Conservation Areas (WCAs). The roles that the canal sediments play in maintaining P levels in EAA canal waters are largely unknown; thus measures of internal loading and

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33 EPC values of the EAA canal sediments are critical to determining the P status and extent of P loading in the sediments. 1.4 .3 Mineral S olubility and Internal P L oading P hosphorus flux from the sediments to the overlying water column can be controlled by mineral solubility (Haggard, 2005). Oxygenated water has a redox potential of around +500 mV but the potential decreases rapidly below the sediment surface and anoxic and reducing conditions predominate (Bostrm et al., 1982). At sediment depths > 1 cm redox potential s < 200 mV and oxygen concentrations ~ 0.1 mg L1Mineralogical studies on the presence or absence of mineral P forms in the canal sediments can explain the P dynamics in canal sediments. Non apatitic CaP com pounds were found in the l ake Apopka sediments suggesting that P in the sediments was due to the P coprecipitation with CaCO can develop (Bostrm et al., 1982). Amorphous Iron (III) oxides and hydroxides are reduced at Eh values around 200mV, thereby releasing phosphate to the water column (Bostrm et al., 1982). 3 1.4 .4 Organic P and Internal P loading (Olila and Reddy, 1995) Sediments in l ake Okeechobee contained quartz and calcite but no P associated minerals (Olila et al., 1994). The lack of crystalline forms of CaP minerals was attributed to insuffic ient time for mineral formation or inhibition in mineral formation by humic acids or other ions (Harris et al., 1994). Organic P can occur i n dissolved, particle associated and colloidal forms and can contain a wide variety of compounds including phospholipids, nucleic acids, inositol phosphates, phosphoproteins, sugar phosphates, phosphonic acids, humic associated organic compounds, polyphosphates and pyrophosphates (McKelvie, 2005).

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34 Condensed P compounds such as polyphosphate and pyrophosphate, are termed biogenic P i.e. inorganic P compounds derived from organic compounds (Hupfer et al., 2004). Hupfer and Lewandowski ( 2005) showed that or ganic P compounds can influence internal loading of P. Ahlgren et al. ( 2006) studied Baltic sea sediments and concluded that degradation of organic P compounds were involved in the internal loading from the lake sediments. Enzymes like alkaline phosphatase s are thought to hydrolyze organic phosphate esters thereby releasing dissolved P (Bostrm et al., 1982). Robinson et al. (1998) conducted 311 5 Research Objectives P NMR spectroscopic studies on the wetland soils of Apopka Marsh, Eustis Muck Farm, an d Sunny Hill Farm (SHF) Florida and identified phytate along with different inorganic ortho P esters and organic mono and diesters. Pant et al. ( 2002) identified p olynucleotides, nucleoside monophosphates, and glycerophosphoethanolamine and phosphoenolpyr uvates in inflow sedi ments of STA 1W. Turner et al. ( 2006) identified inorganic orthophosphate, phosphate monoesters, DNA and pyrophosphate in sediments from STA 1W. Turner and Newman ( 2005) found phosphate, phosphate monoesters, DNA, and pyrophosphate in the sediments of WCA 1 and 2A. Confirming the presence or absence of the organic P compounds in the canal sediments should help determine whether the canal sediments are the source of these organic P compounds to the EAA canals and downstream ecosystems. K nowledge about the physical and chemical properties of the EAA canal sediments is important to enhance our understanding of the entire Everglades system. S ediment properties can affect the water quality in the canals as well as downstream ecosystems, owing t o the easy transportability of the sediments.

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35 The objectives of this research were to: Determine the spatial variability of EAA farm canal sediments with respect to physicochemi cal properties and P fractions ( Study 1,Figure 11). Determine the spatial variability of EAA main canal sediments with respect to physicochem ical properties and P fractions ( Study 2, Figure 12). Determine the P release potential of the EAA canal sediments ( Study 3, Figure 12) Determine the EPC values of the sediments by adsorpti on isotherm and incubation studies ( Study 4, Figure 12) 1.6 Dissertation Format The dissertation consists of four major studies to address objectives in a manuscript format. Chapter 1 includes literature review of factors influencing P releases from marine, lake and stream sediments. Thereafter, the literature review focuses on EAA. Chapter 2 evaluates the physicochemical properties and P fractions of the EAA farm canal sediments. Chapter 3 evaluates the EAA main canal sediments with respect to their physicochemical properties, P fractions and mineralogical properties. Attempts are made to understand th e P release potential of main can al sediments using information on sediment physical and chemical properties. A detailed site desc ription of the farm and main canals are provided in Chapter 2 and 3. Sediment P fluxes from main canal sediments were determined using an incubation experiment that is reported in chapter 4. Chapter 5 is on the evaluation of the Equilibrium Phosphorus Conc entrations (EPC) of the main canal sediments that was performed using two separated experiments; incubation of sediment cores and adsorption isotherm. Overall summary and conclusions are presented in Chapter 6. .

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36 Farm canals Main canals 1a. Physicochemical properties 1b. Phosphorus fractionation Study 1: Characterization of farm canal sediments EAA canals Figure 11 Flowchart of the different experimental steps performed upon the EAA farm canal sediments.

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37 Figure 12 Flowchart of the different experimental steps performed upon the EAA main canal sediments.

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38 CHAPTER 2 PHYSICOCHEMICAL CHARACTERISTICS AND PHOS PHORUS FRACTIONS OF THE EVERGLADES AGRIC ULTURAL AREA (EAA) F ARM CANAL SEDIMENTS. 2.1 Introduction 2.1.1 Historical Background The original Florida Everglades watershed was a broad, freshwater marsh that extended from what is now the Kissimmee River basin, through l ake Okeechobee, to the southern tip of the Florida peninsula consisting of an area of more than 10,000 km2 (Light and Dineen, 1994). The historic flow arising from a nearly flat land slope was at very low velocity from north to south. Historically the Everglades was a contiguous wetland rich in organic soils that was drained for agriculture by the construction of over 2500 canals and levees and hundreds of water control structures (Light and Dineen, 1994). Presently the Everglades is fragmented into the Everglades Agricultural Area (EAA), the Water Conservation Areas (WCAs) and the Everglades National Park (ENP). The EAA presently comprises of 2,872 km2Agriculture in EAA is focused on sugarcane but other crops like corn, winter vegetables and sod are also grown (Bottcher and Izuno, 1994). The hydrology of the of organic soils (SFER 2010b ) drained during 1953 to 1967 by the US Army Corps of Engineers for flood protection and agricultural production (Chimney and Goforth, 2001). The wetland remains of ENP, the WCAs and the Holeyland and Rotenberger Wildlife Management Areas is considered an ecosystem of immense importance because it contains a multitude of habitats that supports unique biotic communities. Everglades National Park, the largest subtropical wilderness in the United St ates has been declared as a Wetland of International Importance under the 1987 Ramsar Convention, an International Biosphere Reserve and as a United Nations World Heritage site and (Maltby and Dugan, 1994).

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39 EAA is managed by the South Florida Water management District (SFWMD) and the region is drained by network of field ditches and canals. Nutrient rich agricultural drainage water is pumped from the farm canals to the main canals and, the WCAs and finally discharged into the downstream ecosystem including the ENP. The farm canals are used to irrigate and drain the farms which drain into the main canals. The main canals originate from l ake Okeechobee and ultimately drain into the Atlantic Ocean (Light and Dineen, 1994). Native Everglades vegetation including sawgrass and upland pine ( Pinus spp ) is adapted to low nutrient levels and is P limited (Davis and Ogden, 1994) N utrient enrichment from EAA agricultural drainage, specifically phosphorus (P), has been identified as one of the causes of ecosystem changes in the WCAs and the ENP (LOTAC., 1990; Whalen et al., 1992). About 129 metric tons of total P load wit h total P concentration of 119 g L1 from the EAA was estimated to have been discharged in 2009 (SFER, 2010a ). To mediate the environmental changes, restoration efforts have focused on reducing nutri ent loading from EAA and restoration of a more natural hydroperiod to sensitive wetland areas of WCAs and ENP (Light and Dineen, 1994). Current remediation plans require area growers to implement Best Management Practices (BMPs) in EAA. Practices include m odifying pumping practices, protecting canal banks with vegetation, minimizing fertilizer application, using cover crops, and retaining of on farm drainage to reduce P discharge to the canals of the EAA ( SFER 2003; SFER 2002). To further treat agricultur al drainage water, several wetlands called Storm Treatment Areas (STAs) have been constructed in the southern edge of the EAA.

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40 2.1.2 Phosphorus in the EAA Agricultural farms in EAA are privately owned and managed by growers. The farms are drained by farm c anals that discharge into the EAA main canals. Along with the flow of water, canals can carry suspended solids, nutrients and other constituents from the farms can either accumulate or be further transported depending upon the canal management practices. Phosphorus in the EAA farms can be sourced from fertilizer application to agricul tural farms, inflow water from l ake Okeechobee or the mineralization of the organic soil (Stuck 1996). Historically before the initiation of farming rainfall was the dominant source of P in the Everglades (Davis 1994). Phosphorus sorbed by soil particles and organic materials is termed particulate P and consists of solid phases of P (Diaz et al., 2005). Particulate P constitutes about 20 to 70% of the total P exported from EAA farms (Izuno and Rice, 1999). The P in organic particulate P consists of a mixture of detrital water weeds, and planktonic growth that can range from 15003500 mg kg1 and 900015000 mg kg1 resp ectively (Daroub et al., 2002a). Particulate P in agricultural residues in EAA is highly variable and varies with land use and management practices. Farms in EAA grow different crops with different fertilizer requirements and management practices. In a study conducted by the engineering firm CH2M Hill (1978), vegetable farms in EAA were shown to have an annual total P load four times than that of sugarcane farms. Canal management factors like pump velocity, canal depth and canal maintenance can determine parti culate P load from canals (SFER 2004). The pump operated water movement in EAA is characterized by rapid hydrodynamic changes that are different than a natural system thus causing the EAA canal systems to undergo changes from static conditions to very high velocities (Daroub et al., 2002b). Hydraulic quiescence period in canals can

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41 facilitate particulate deposition and increase the concentration of organic particulates (Engle and Melack, 1990) subject to remobilization during flow conditions (Daroub et al. 2002b; Svensdsen et al., 1995). Good aquatic weed management program can prevent accretion of particulate P in farm canals resulting in lower total P and organic matter content than in canals that do not have similar management programs. The light and flocculent nature of the predominantly organic particulate matter is easily transportable to the downstream ecosystems (SFER 2004; Dierberg and DeBusk, 2008). Accumulation of particulate matter can lead to higher total P and organic matter content on the surface sediments compared to the subsurface sediments, as has been observed in the Everglades (Newman et al., 1997; White and Reddy, 2001, 2003). P hysicochemical properties of EAA farm canal sediments can be vary with the geological ( mineralogical ) comp osition of bedrock at that location. The presence of calcium carbonate bedrock can also influence sediment properties including pH, mineralogical composition and distribution of P fractions. The calcium carbonate bedrock in combination with the biological nature of particulate P can influence the sediment physical and chemical properties in EAA canal sediments. The heterogeneous mixture of organic matter with various levels of P content have variable transport properties (SFER, 2004), which can lead to changes in sediment properties within different locations of a canal. Other factors leading to differential physicochemical properties along canals can be changes in sediment depth, varying degree of incorporation of limestone into sediments, presence of struc tures obstructing sediment transport.

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42 Due to the underlying limestone bedrock and the accumulation of particulate matter on top, the EAA canal sediments are very different from either organic or mineral soils. The biological nature, the heterogeneity of the suspended solids, varied erosion rates, sedimentation velocities, and rates of disengagement of attached plant growth, result in dynamic changes in the sediments and the overlying water column that may not occur in systems that are predominantly mineral in nature (Daroub et al., 2002a). The differences in the mobility and reactivity of the P stored in EAA canal sediments are controlled by the chemical composition and f orms of P in sediments. The ability of sediments to store or release P has repercussion on water quality as well as on management and restoration strategies. The detailed study of sediment P fractions is critical to a better understanding the P cycle in the EAA canals. 2.1.3 Phosphorus Fractionation Phosphorus fractionation allow s us to distinguish and quantify both inorganic and organic pools of P, and the recalcitrance of these P pools. P hosphorus availability from different P pools can determine the mobility of stored P which can affect water quality of the canals. Phosphorus f ractionation methods are operationally defined and involve selective dissolution of different P forms in different solvents (Ivanoff et al., 1998). Loosely bound P or labile P is extracted using salt solution s like KCl, NH4Cl and NaCl (Re ddy and Delaune, 2008). Following the extraction of loosely bound P, alkali (NaOH) is used to extract Fe and Al bound P. A cid (HCl) is subsequently used to extract Ca and Mg bound P. Other alkali extractants used by researchers to extract Fe and Al bound P, are NaOH with ci trate ditionite bicarbonate (CDB). Hieltjes and Lijklema, (1980) concluded that NaOH and CDB was unsuitable for the extraction of Fe and Al bound P in calcareous sediments because the strongly complexing citrate solubilizes substantial

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43 quantities of Ca bou nd P. R esidual P is the P fraction left when all other P fractions i.e. labile P, Fe and Al bound P and Ca and Mg bound P are extracted. The residual P is considered to be mostly recalcitrant organic P or P that is occluded into mineral matter. Phosphorus fractionation procedures have been used to investigate the transformation and P movement in upland soils (Tiessen et al., 1983; Beck and Sanchez, 1996), organic wetland soils (Ivanoff et al., 1998), lake sediments (Hieltjes and Liklema, 1980) and calcareous sediments (Clark and Reddy, 2002). In South Florida, White et al. (2004) performed inorganic P fractionati on (KCl NaOHHCl) on sediments from STA 1W and found that the Ca phosphates and residual P accounted for more than 75% of total P with half of all P present as organic P Phosphorus fractionation on sediment samples of the WCA 1 performed by Newman et al. (1997) showed that almost 70% of the total P was organic in nature. The constructed wetlands in Everglades or the STAs operate as flow through treatment systems to reduce phosphorus levels entering the Everglades by removing P through emergent aquatic vegetation, submerged aquatic vegetation, periphyton and sediment accretion ( Chimney and Goforth, 2010) The WCAs are shallow diked marshes maintained for flood control, water supply, and environmental restoration. The hydrologic regime and vegetation in wetlands promote accumulation of organic matter due to low decomposition rates under flooded conditions ( DeBusk and Reddy, 1998) resulting in organic matter accumulation rates in the WCAs in the order of millimeters per year and in the Everglades about cm s per year (Craft and Richardson, 1993; Reddy et al., 1993). High organic matter accumulation rates in the Everglades wetlands result in higher organic P than in EAA canal sediments.

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44 The KCl NaOHHCl fractionation scheme was applied by Diaz et al. (2006) on the canal sediments within the STAs to evaluate the different inorganic and organic fractions of P. They found that Ca and Mg bound P and residual P were the dominant P forms in these canals. Though successfully performed on the sediments and soils of the STAs and the WCAs, this fractionation scheme has not been used to analyze the canal sediments within EAA. We hypothesize that the (i) physic ochemical properties of EAA farm canal sediments vary with depth (surface and subsurface layers) and between locations in the farm canals, and (ii) sediment P fractions vary with depth (surface and subsurface layers) and between different locations within the farm canals. The objectives of this study were to (i) characterize physicochemical properties in surface (05 cm) and subsurface (510 cm) sediments from different locations of three EAA farm canals and (ii) characterize sediment P fractions in surface (0 5 cm) and subsurface (510 cm) sediments from different locations of three EAA farm canals. 2.2 Material and Methods 2.2.1 Site Description and Sample Collection Sediments were collected from three farm canals : UF9209A (09A) situated in the western part of the EAA; UF9200A (00A) situated in the eastern part of EAA ; and UF9206AB (06AB) located in the southeastern EAA near STA 1W (Figure 21). Farm 09A is a large (12.4 km) sugarcane monoculture farm drained by three manually operated pumps (6.3136.8 m3 min1 range). Farm 09A is situated within Terra Ceia (Typic Haplosaprists) and Pahokee (Lithic Haplosaprists) soil map units Depth to bedrock range from 50.8 91.4 cm (West Palm Beach Soil Survey, 1978) at farm 09A, which is situated in the S8 basin (Fi gure 21). Farm canal 09A represents a large farm

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45 with a large canal relative to pump capacity and the farm canal has low velocity (0.13 m s1Farm 00A is located in the eastern part of EAA and i s a medium size (5.18 km) sugarcane monoculture farm It is drained by two high capacity (9.46 29.44 m ) (SFER 2004). Owing to low pump velocity and moderately large canal depth (0.98 m) (Daroub et al., 2009), farm c anal 09A sediments are slow to mobilize or have long response times (SFER 2004). Particulate P from farm canal 09A averaged about 70% of total P (SFER, 2004). Farm canal 09A drains into the Miami canal. 3 min1 range), and one lower capacity (5.28.93 m3 min1Farm 06AB is a medium size (7.08 km) mixedcrop farm located in the S 5A sub basin in eastern part of EAA. Farm 06AB consists of Terra Ceia (Typic Haplosaprists) and Pahokee (Lithic Haplosaprists) soil series and depth to bedrock ranges from range) single speed electrical pumps with automatic onoff level control. Automatic level controls ensure that the farm canal is drained regularly and that water is not held up for a long time, which prevents the accumulation of p articulate P. Farm 00A consists of Terra Ceia (Typic Haplosaprists) and Pahokee (Lithic Haplosaprists) soil series with depths to bedrock >129.5 cm and 91.4129.5 cm respectively. Farm 00A is situated within the S5A farm basin and has average sediment dredging program and clean the canal s a s necessary. Average sediment dredging program consists of cleaning canals when thought necessary by the farm owner in contrast to a periodic program. T here was no major canal work conducted on farm canal 00A over a period of four years (S FER 2004) Fa rm canal 00A sediments ( due to high velocity flow in the canals) responds faster than farm canal 09A sediments, i.e. farm 00A sediments are likely to be transported than 09A canal sediments. Farm 00A receives irrigation water and discharges into the West P alm Beach canal

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46 >129.5 cm and 91.4129.5 cm respectively. Farm 06AB has two pump stations, each with two high capacity diesel pumps. This farm is partitioned into multiple hydraulic units and has a sophisticated hydraulic system with culverts, risers and booster pu mps placed strategically throughout the farm. Farm 06AB includes multiple control structures that allow an aggressive water management program that prevents build up of partic ulate P in the farm canal (SFER 2004). Farm 06AB has depth 0.88 m (Daroub et al. 2009) lower than both farm canals 09A and 00A. Farm canal 06AB has the highest average velocity 0.27 m s1Sediment cores were collected from five transects within each of the three farm canals (Figure 21). The first transect (T1) was near the intersection where the farm canals drain into the main canal, i.e., where farm canal 00A drains into the West Palm Bea ch canal 09A drains into the Miami canal and the 06AB drains into the Ocean canal The remaining four transects (T2, T3, T4, and T5) of each canal were taken progressively away from T1 into the central part of the canals Triplicate sediment cores were collected at each transect within the middle two thirds of the canal cross sectional area. which causes particulates in the canal to mobilize faster than both 09A and 00A. Thus canal 06AB is likely to have greater mineral matter content t han the deeper 09A (0.98 m) and 00A (1.16 m) canals as the light and flocculent particulates could be tr ansported along the canal (SFER 2004). Irrigation and drainage in farm 06AB is accomplished through farm canal 06AB which drains into the Ocean canal. All the transect locations (T1 to T5) in each of the canals were georeferenced by the GPS coordinates using a Trimble Unit Pro XR DGPS Unit (Trimb le Navigation

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47 Limited Mapping and GIS Systems, Sunnyvale, CA). The GPS position and the distance between transects are given in Appendix A (Tables A1, A2 and A3). At each transect location two steel rebars were installed at the edge of the water on each side of the canal. D uring sediment sampling, a steel cable was attached to the rebars to anchor a boat used during measurements. Sediment cores were collected using a sediment sampler fitted with a polycarbonate core that was inserted on the sediment bed. The sampler along wi th the core was then quickly pulled up into the boat, stoppered at both ends and transported upright to the laboratory. The sediment cores were stored at 4oC until sectioned, which was done within 24 h of sampling. The water in the columns was removed by v acuum suction and the sediment sectioned at depth increments of 05 cm and 510 cm. Sediment samples were stored in plastic jars at 4o2.2.2 Sediment Analyses C until analysis. A total of 3 replicates were taken from each of the 5 transects from each canal leading to 15 sediment c ores from each canal, totaling up to 45 cores from the three canals. All sediment samples were analyzed for total P, bulk density (BD), %Loss on ignition (%L OI) and pH. Loss on ignition was determined by combusting an ovendried sed iment sample at 550oC for 4 h in a muffle furnace, and the weight loss was considered a measure of the organic matter content. (Andersen, 1974) This method was based on the principle that, at the chosen temperature, all organic carbon was converted to CO2, whereas loss of CO2 from carbonates and loss of water from clay minerals are negligible. Thermogravimetric studies using standard calcium carbonate by Kasozi, ( 2007) indicated that the required activation energy needed for decomposition of calcium carbonate necessitates a temperature of at least 600oC. Kasozi, ( 2007) concluded that the decomposition of calcium carbonate was energy reliant rather than

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48 temperature reliant. Similar results using t hermogravimetry were also observed by Singh and Singh ( 2007 ) The atmospheric partial pressure of CO2 is 0.00035 Pa. It is suggested that, in a closed furnace undergoing decomposition of CaCO3 the parti al pressure of CO2 can increase which necessitates high temperature of decomposition (Lide, 2005). In fact there has been attempts to lower the calcium carbonate decomposition temperature using carboxylic acids primarily to save energy in the cement industry (Kasselouri et al.,1995) The ash from the muffle furnace was digested with 6N HCl and analyzed for total P using the ascorbic acid method (Method 365.4, U.S. Environmental Protecti on Agency, 1983) using an Alpkem segmentedflow 650 nm analyzer (The limit of detection for the Alpkem analyzer was 0.007 mg L1). Bulk density was measured by placing 10 g of sediment in glass beaker in an oven at 105oThe P fractionation scheme developed by Reddy et al., 1995, 1998 was used in this s tudy. The five step fractionation included of both organic (o) and inorganic (i) fractions of P: KCl extractable P (KCl Pi), NaOH extractable P, HCl extractable P (HClPi), and residual P (ResidueP). The KCl Pi fraction represents the labile Pi that is water soluble and exchangeable (loosely adsorbed); NaOH extractable P represents Feand Al bound inorganic P (NaOH Pi) and organic P associated with humic and fulvic acids (NaOH Po). The HCl Pi are the Caand Mg bound P, while ResidueP represents recalc itrant organic P compounds and P bound to minerals. C for 12 h. Sediment pH was determined by weighing 10 g of sediment and adding 20 mL of DI water (mass to volume ratio 1:2 ) (Thomas, 1996). The fractionation procedure involves sequential extraction of 0.3 g dry sediment equivalent of wet sediments with 1 M KCl, 0.1 M NaOH, and 0.5 M HCl solutions in that

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49 order. Residual P fraction was determ ined in the residues left after solution extractions and involved ashing followed by dissolution with 6N HCl acid. Details of the fractionation are given in Reddy et al. ( 1998) Concentrations of P in the filtrates of each sequential extraction and the aci d digestion were determined by colorimetry using Spectronic 20 Genesys spectrophotometer and Lachat Quickchem FIA 8000 series (Murphy and Riley, 1962). Quality assurance/quality control was strictly followed with calibration, standards, spikes, and blanks routinely included in the analysis. A check standard was included every 10 samples and a duplicate after every 10 samples. A spike was included for every 20 samples. The limit of detection for the Lachat Quickchem was 0.001 mg L12.2.3 Statistical Data Analysis Descriptive statistics of means, standard deviation and standard errors (proc MEANS), were performed on data collected from the sediment sample analysis using SAS statistical program (SAS Institute, 2003). Normality and goodness of fit tests were conducted to check the distribution patterns of the physicochemical properties and P fractions data. Where the data were not normally distributed, log transformations were used to stabilize the variance, and make the residuals Gaussian distributed for par ametric analysis. Analysis of variance (ANOVA) was used to compare sediment physico chemical properties and P fractions between canal transects (USEPA 1989). Summary statistics were conducted and Tukey test were used (SAS Institute, 2003) to assess signi ficant differences between physicochemical properties, P fractions between transects within each farm canal and between the canals.

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50 2.3 Results and Discussion 2.3.1 Physicochemical Properties Sediment physicochemical properties varied between transects, ca nals, and canal depths, (Table 21, Table 2 2 and Table 23 and Table 24 respectively ). The sediment total P values of farm canal 09A in the 05 cm layer varied from 571 mg kg1 at T4 to 1110 mg kg1 at T1. In canal 00A total P varied from 928 mg kg1 a t T5 to 2460 mg kg1 at T3. For canal 00A at depth 510 cm total P values varied from 480 mg kg1 at T1 to 221 0 at T3. Canal 06AB total P values at 05 cm varied from 344 mg kg1 at T1 to 742 mg kg1 at T4. The total P content for the 510 cm layer did not vary significantly among the five transects of farm canals 09A and 06AB and averaged 636 mg kg1 and 569 mg kg1Bulk density values of farm canal 09A did not vary significantly among transects and averaged 0.19 g cm respectively Both at the 05 and 510 cm depths the average total P values followed the trend 00A>09A>06AB i.e. canal 00A had greater tota l P values while 06AB had smaller total P values. Total P of sediments decreased with depth for farm canal 09A and 00A. High total P at 05 cm layer could be due to higher P content of accumulated detrital matter. Similar trends of decreasing total P with depth have been found by researchers in sediments of the Everglades region (Reddy et al., 1993; Newman et al., 1997; White and Reddy, 2001, 2003). There was no change in total P values with depth for 06AB canal sediments. Aggressive aquatic weed control and canal cleanup operations possibly have prevented accumulation of high P content detrital matter on the surface resulting in no change in total P content at depths 05 and 510 cm layers. 3 at 0 5 cm. Bulk density values varied from 0.080.16 g cm3 and 0.240.54 g cm3 at depth 05 cm for farm canal 00A and 06AB respectively. At 510

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51 cm layer the bulk density values varied from 0.190.56 g cm3, 0.1 0 0.5 0 g cm3 and 0.290.5 0 g cm3 for farm canals 09A, 00A and 06AB respectively. Similar bulk density values ranging from 0.10 0.6 0 g cm3 were found by Diaz et al. (2006) in the canal sediments of the STAs and the WCAs of the Everglades. Studies performed by Reddy et al. (1998) on the EAA soils yielded average bulk density value of 0.42 g cm3. Bulk density values in the sediments of the farm canals are lower than typical bulk density values of mineral soils. These low bulk density sediments thus are susceptible to be transported in the EAA drainage waters as suspended load distributed throughout the water column (Daroub et al., 2002b). Mineral soil bulk density values range from 1.01.6 g cm3 in fine textured soils and 1.21.8 g cm3 in coarsetextured soils (Brady et al., 2002). Bulk density values at 510 cm layer were higher than that at 05 cm layer in all farm canals. This increase in bulk density with depth can be due to increased incorporation of limestone into sediments and compaction. Lower bulk density values at 0 5 cm layer were possibly the consequence of deposition of detrital matter. Bulk density values in the surface sediments of WCA 2A were found to be 0.049, 0.050, 0.052, 0.070 g cm3 at the surface 010 cm depth compared to 0.086, 0.104, 0.094 and 0.092 g cm3 at subsurface 1030 cm depth (White and Reddy, 2000). Average bulk density values determined in STA 1W by at surface 0 5 cm and 530 cm layer were 0.306 g cm3 and 0.369 g cm3 (White et al., 2006). The narrow range of difference between the surface and subsurface bulk density values at the STA 1W is attributed to the incorporation of limestone in the surface layers of the soil. The smallest bulk density values among the three farm canals were observed in sediments of 00A canal in both

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52 surface and subsurface sediments whereas the greatest bulk density values were observed in farm canals 06AB and 09A at depth 510 cm. Th e %LOI values of farm canal 09A did not vary significantly among transects at both depths and averaged 31.8% at both 05 cm and 510 cm layers (std dev 5.18 and 5.27) For farm canals 00A and 06AB at 05 cm depth %LOI values varied from 41.957.4% and 13. 9 41.6% respectively. At 510 cm depth for farm canal 00A %LOI values varied from 16.473.6% while for farm canal 06AB, %LOI values did not vary significantly among transects and averaged 30.1%. Among all the three farm canals, canal 00A had the high %LOI values (74.2 and 73.6%) at both 05 and 510 cm depths. Both canal s 00A and 06AB have smaller %LOI at T1 which is probably due to the close proximity of pumps that effectively mobilize the light and flocculent sediment surface layer. The canal %LOI values followed the trend 00A>09A, 06AB both at the surface and subsurface layers. The %LOI values decreased with depth for 00A canal but the values were not significantly different at either depth for 09A and 06AB canals Sediment pH values between different tr ansects were not significantly different at the 05 cm layers of 09A and 00A canals and 510 cm layer of 09A canal. The average pH values of canal 09A, 00A at 05 cm sediment layer and 09A at 510 cm sediment layer were 7.5, 7.1 and 7.5 respectively. Both at surface and subsurface layer farm canal 00A had smallest pH values at both the surface and subsurface layers (7.1 and 7.2), while 06AB had the greatest pH values of 7.7 at both the layers. The circum neutral values of the sediments are most likely due t o incorporation of limestone from the limestone bedrock. Similar pH values have been found in the sediments of the

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53 Everglades region including WCA 2 (7.2), WCA 3 (6.7) and Holey Land Wildlife Management Area (7.5) (Reddy et al., 1998). 2.3.2 Phosphorus Fra ctions of EAA Farm Canals Sediment KCl Pi comprised an average of 1 to 2% of total P at the 0 5 and 510 cm layer (Figure 22 and Figure 23) and the values were not significantly different between transects of farm canal 09A, 00A and 06AB (Table 25 ). Farm canal 00A had the greatest KClPi value at the 05 cm layer while at 510 cm layer there were no significant differences in KCl Pi values between the three farm canals (Table 26 ). Phosphorus stored in KCl Pi is of concern because it represents the readily available P pool. However, the low KCl Pi values in the farm canal sediments were in accordance to those reported by various researchers in South Florida, 0.12.3% of total P in stream sediments of l ake Okeechobee watershed (Reddy et al., 1995), 0.3 3% in the organic soils of Everglades (Reddy et al., 1998), <1% in the canal sediments of the Everglades (Diaz et al., 2006), 0.01% of total P in the mesocosm of STA 1W (White et al., 2006). White et al. (2004) found an average KCl Pi value of 2.99 mg k g 1 in the mesocosms of the Everglades Nutrient Removal (ENR) Project (STA 1W). In contrast the concentrations of readily available P measured by 1M NH4Cl varied between 10 to 2 4% in the surface sediments in l ake Apopka and 1017% of total P in the littora l and peat sediments of l ake Okeechobee (Olila et al., 1995). The authors concluded that this fraction could act as a source of P to the overlying water and may be important in internal P cycling (Olila et al., 1995). The variations in the ionic strength and water to soil ratio can cause variation in P desorbed. Both procedures using (KCl and NH4Cl) used the same soil to solution ratio, same concentrations of the extractant (1 M) and the same shaking time (2 h) for extracting labile P. Since both KCl and NH4Cl are ionic salts

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54 and dissociate completely in aqueous solutions, the resulting ionic strength of the aqueous solutions can affect the quantity of P desorbed thus changing the labile P estimates. P desorption experiments conducted on soil consecutively w ith reverse osmosis water, a 50:50 mix of reverse osmosis water and well water, and 0.01 M CaCl2 yielded progressively lower dissolved P concentrations (Turner et al., 2002). Similar results were obtained by McDowell and Sharpley ( 2001) using water and 0.0 1 M CaCl2 n icizi I1 22 / 1 Thus increasing the ionic st rength of the solutions yielded progressively lower dissolved P concentrations. Since the ionic strength ( where ci=concentration and zi=charge) are both same for the extractants I would expect no significant differences in labile P estimates by 1M KCl and 1M NH4The NaOH Pi fraction comprised 47% of total P in the 05 cm layer and 57% of total P in the 510 cm layer of t he canal sediments and did not vary significantly between transects except 510 cm layer of 00A canal. Average NaOH Pi values at 09A canal at 05 and 5 10 cm layers were 68.9 and 43.3 mg kg Cl. 1, at 00A canal 74.4 and 62.4 mg kg1 while at 06 AB canal the values were 15.2 and 9.32 mg kg1. Mean NaOH Pi values of 09A canal and 00A were significantly higher than for 06AB at both 05 cm and 5 10 cm layers. The NaOH Pi fraction consists of P associated with amorphous and crystalline Fe and Al oxides and oxyhydroxides that can act as a potential long term source of P to the water column under fluctuating redox conditions (Hieltjes and Lijklema, 1980; Olila et al., 1995). Phosphorus fractionation studies by Diaz et al. (2006) on the canal sediments of the STA and the WCA canals found that the NaOH Pi fraction varied from 113% of total P. The Fe and Al bound P is usually relatively stable, but is subject to changes in sediment physicochemical properties like changes in redox

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55 potential (Moore and Reddy, 1994) whereby it can get reduced. The reduced form of Fe being more soluble can be released from the sediments to the water column (Mortimer, 1941; Holdren and Armstrong, 1980). Drastic decreases in dissolved oxygen concentrations can occur during summer when high primary productivity and subsequent degradation can result in high sediment oxygen demand (Moore and Reddy, 1994). Redox fluctuations are more likely in sediments with high organic matter, high primary productivity or low flow velocities or pulse flow (Diaz et al., 2006). This is particularly important as water flow in EAA farm canals are not continuous but are regulated by pumps Such conditions result in pulsed flow including quiescent noflow periods between pumping events that favor accumulat ion of detrital material in the canals (Daroub et al., 2002a). The NaOH Po values did not vary significantly between transects in farm canal 09A and 00A T he average NaOH Po values in canal 09A at 05 and 510 cm layers were 121 and 82.3 mg kg1 respectively. I n canal 00A the average NaOH Po values at depth 05 and 5 10 cm were 38.0 and 17.7 mg kg1. Farm canal 06AB, NaOH Po values ranged from 18.439.4 mg kg1 at the 0 5 cm and 15.331.6 mg kg1 at the 5 10 cm layer. Canal 09A had significantly higher NaOH Po values than 00A and 06AB canals. The NaOH Po fraction represented about 314% of total P in the surface sediments of all three farm canals. The NaOH Po fraction represents P bound to humic and fulvic acids and is susceptible to hydrolysis and subsequent release (Bowman and Cole, 1978; Ivanoff et al., 1998). Qualls and Richardson (1995) and Reddy et al. (1998) suggested that the deposition of NaOH Po in the Everglades was due to vegetative upt ake and detrital deposition. The decom position of the NaOH Po pool depends on the

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56 availability of oxygen and this P pool is relatively stable under hypoxic conditions. Ivanoff et al. (1998) found that NaOH Po values in a drained agricultural farm, pasture in EAA and flooded soils (ENR project) comprised of 74%, 68% and 54% of total P and concluded that the soils of the three Histosols were highly humified. In the EAA canals, the deposition of detrital matter is not favored due to canal hydrology and managem ent practices In the Everglades as a result of hydrology and accumulation of nutrients the organic P forms are dominant forms of P storage. The hydrology in EAA canals is very different than that in the rest of Everglades governed primarily by canal manag ement practices that includes use of pumps resulting in rapid changes in water velocity, canal management practices including re moval of canal aquatic weeds that does not promote accumulation of organic P Thus the NaOH Po content is lower than the sedimen ts in Everglades. Phosphorus bound to Ca and Mg minerals (HCl Pi) was the dominant fraction at both depth 05 cm and 5 10 cm at all the three farm canals and at all the transects. The HClPi fraction at the three farm canals accounted for 5159% of the to tal P in the 0 5 cm level and 5661% of total P at the 510 cm depth. High levels of HClPi were also found in other parts of the Everglades. Sediments from WCA 1 were found to have HCl P ranging from 3247% and 9 16% of total P in the cattail dominated ar eas and interior marshes respectively (Reddy et al., 1998). The values of HCLPi in W CA 2A WCA 3A, Holey Land Wildlife Management Area varied as 3546% 80% and 53% and 44% of total P respectively. The HClPi ( Ca bound P fraction) also dominated (64% of total P) in the canal sediments of North Miami canal and South Miami canal (Diaz et al., 2006). White et al., 2004 found that HCl Pi fraction and the residue comprised more than 75%

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57 of the total P in the ENR project. The Ca and Mg bound P represented about 64% of t otal P in the mud sediments of l ake Okeechobee (Olila et al., 1995). The greates t concentrations of HCl Pi (1210 mg kg1) were measured in sediments from the 00A canal at depth 05 cm and the smallest concentrations (245 mg kg1Residue P was the second greatest P fraction in all the three farm canal sediments and comprised of 24.940.9% and 25.438.9% of total P at the 05 and 510 cm layers respectively. Similar residual P values were f ound by Diaz et al. (2006) in the canal ) in sedim ents of 06AB canal (Table 27 ). Mean HCl Pi values of the three farm canals followed the order 00A>09A>06AB at both 05 and 510 cm layers (Table 28 ). The HClPi is relatively stable and P release from this fraction should be comparatively slow (Sonzogni et al., 1982). The region extending from l ake Okeechobee to Florida Bay is underlain, by a series of alternating porous layers of limestone, shell, sand and marl (Jones, 1948) that allows the interaction of ground and surface water resulting in high pH and Ca concentrations (Noe et al., 2001). Drainage water from the EAA is also high in Ca and Mg concentrations (Diaz et al., 1994). Precipitation of the Ca and soluble P as phosphate minerals has been reported by Diaz et al., 1994 in the EAA drainage waters w ith high Ca concentration and pH values. In addition to precipitation of calcium phosphates, deposition of Ca bound P in EAA canals can result from coprecipitation with calcium carbonate or adsorption/precipitation of phosphates on calcium carbonate surfac es. Richardson and Vaithiayanathan (1995); Reddy et al. (1998) have shown extractable Ca and Mg to be significantly correlated with extractable HCl Pi in the WCAs. However the determination of the nature of the association of the P with the Ca is subject t o mineralogical analyses of the sediments.

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58 sediments of North and South Miami canal (2135% ). Residue P in canal 09A was not significantly different between transects and averaged 225 mg kg1 at 0 5 and 166 mg kg1 at the 510 cm layer. Residue P val ues varied from (49.4 305 ) mg kg1 in farm canal 00A and (111247) mg kg12.4 Conclusions in farm canal 06AB at the 05 cm. Both at 05 and 510 cm layers farm canal 00A had higher residue P values than 09A and 06AB canals. Residual P fraction is considered to be highly resistant and biologically unavailable (Hieltjes and Lijklema, 1980). The residual P pool can consist of stable lignin and organometallic complexes (Ivanoff et al., 1998). Differences in total P, bulk density, %LOI and pH of sediments taken from th e five transects within each farm canal show wide variability in physicochemical properties of EAA farm canals sediments. Total P and %LOI of the canal sediments both at the surface and subsurface layers were in the order of 00A>09A>06AB. Sediment %LOI and BD values were inversely related at 0.0001 probability related (Table 26) and the BD values of the canal sediments followed the opposite trend of %LOI, 00A<09A<06AB at the 0 5 cm layer. The total P values of canal sediments were positively correlated to %LOI content at the 0.0001 probability level, i.e. well managed canals having less detrital deposition will have low total P and low %LOI and vice versa. The bulk density values were inversely related to total P content i.e. sediments with high mineral mat ter due to the presence of carbonates had low total P values. The low total P concent ration of sediments with higher mineral materials could possibly be due to the lack of P containing minerals in the limestone bedrock, but this is subject to further miner alogical studies.

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59 The pH values of sediments followed the trend 06AB and 09A>00A at the surface layer and 06AB>09A>00A at the subsurface layer. The high pH values of canal 06AB at both layers suggest that 06AB canal sediments have higher mineral matter content than 09A or 00A canal. A s ophisticated hydraulic system in combination with an aggressive water management program and shallow canal depth likely promote transport of low bulk density particulate matter in canal 06AB and result in low total P, low %LOI and high bulk density values. Low bulk density and high %LOI values of the surface sediments of farm canal 00A make them susceptible to sediment resuspension and transport to downstream movement especially during high velocity pumping events. There were differences in sediment physicochemical properties in the surface and subsurface layers of the canals. Aggressive canal management of 06AB prevented accretion of detrital matter thus the total P values for surface and subsurface sediments were not differe nt in farm canal 06AB. In contrast farm canals 09A and 00A surface sediments had higher total P than subsurface sediments. Sediment bulk density increased with depth at all the canals which can be due to compaction as well as increased mineral content in t he subsurface layer. Several decades of nutrient loading from the EAA have resulted in the storage of P in the canal sediments This P reserve can lead to P flux in to the water column than can be crucial as this water eventually flows into downstream ecosy stem s including the WCAs and the Everglades National Park. Lower P content in 06AB canal may lead to lower P flux than that of 00A and 09A canals. Higher NaOHPi values in sediments of farm canal 00A and 09A can lead to slow and prolonged P release to the overlying water column. The high HCl Pi (>50 % of total P) in the farm canal sediments suggests

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60 that this pool can be an important long term storag e for P. Calcitic minerals can also be very important in storing P in EAA canal sediments thereby preventing their release into the water column. In contrast to the downstream Everglades ecosystem, organic P in the EAA farm canals ranged from 313% of total P compared to about 70% of total P in the Everglades essentially due to Everglades hydrological conditions promoting organic P retention.

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61 Figure 21 Farm basins and positions of farm canals 00A, 09A and 06AB in EAA Table 21 Total P and bulk density values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depths 0 5 cm and 510 cm. Transect Total P (mg kg 1 ) BD (g cm 3 ) 09A 00A 06AB 09A 00A 06AB -------------------------0 5 cm --------------------------T1 1110 a 1120 b 344 c 0.12 ns 0.12 ab 0.54 a T2 870 ab 1510 ab 519 b 0.16 0.13 ab 0.36 abc T3 757 ab 2460 a 559 ab 0.19 0.16 a 0.44 ab T4 571 c 1590 ab 742 a 0.23 0.11 bc 0.27 bc T5 668 b 928 b 716 a 0.22 0.08 c 0.24 c ----------------------------5 10 cm -------------------------T1 748 ns 480 c 494 ns 0.36 ab 0.5 0 a 0.44 a T2 643 917 b 572 0.33 ab 0.21 b 0.5 0 a T3 586 2210 a 516 0.56 a 0.2 0 b 0.47 a T4 550 1170 b 608 0.36 ab 0.14 bc 0.37 ab T5 653 870 b 653 0.19 b 0.1 0 c 0.29 b Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal and depth. P = 0.05. ns not significant.

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62 Table 22 Percent LOI and pH values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depths 05 cm and 5 10 cm. Transect %LOI pH 09A 00A 06AB 09A 00A 06AB -------------------------0 5 cm --------------------------T1 37.8 ns 41.9 c 13.9 c 7.5 ns 6. 8 ns 7. 8 a T2 36.9 42 .0 c 24.3 abc 7.5 7. 3 7.6 b T3 29.4 74.2 a 24.4 bc 7.5 7.0 7.6 ab T4 25.4 50.1 b 39.5 ab 7.5 7.3 7.6 b T5 32.4 57.4 b 41.6 a 7. 6 7.3 7.7 ab -------------------------5 10 cm --------------------------T1 21.7 ns 16.4 c 20.6 ns 7.4 ns 7. 2 ab 7.8 a T2 27.9 41.3 b 25.1 7. 6 7. 4 a 7. 7 ab T3 22.3 73.6 a 24.4 7. 7 7.0 b 7.7 ab T4 20.8 44.3 b 38.1 7. 6 7. 4 a 7. 7 b T5 33.2 52.3 ab 40.1 7.5 7. 4 a 7. 7 ab Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal and depth. P = 0.05. ns not significant. Table 23 Mean total P, bulk density(BD), %LOI and pH values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depths 0 5 cm and 5 10 cm. Treatment means within the same column followed by the same letter are not different by Tukeys test between canals for each depth. P = 0.05. ns not significant. Canal Total P mg kg 1 BD g cm 3 %LOI pH -------------------------0 5 cm -------------------09A 794 206 b 0.190.05 b 31.8 5.18 b 7.5 0.01 a 00A 1520 592 a 0.120.03 c 53.713.4 a 7.10.25 b 06AB 575162 c 0.370.12 a 28.8 11.6 b 7. 7 0.06 a ------------------------5 10 cm ------------------09A 636 86.5 b 0.4 0 0.08 a 31.8 4.67 b 7.5 0.06 b 00A 1130861 a 0.2 0 0.19 b 45.624.3 a 7.3 0.17 c 06AB 569120 b 0.4 0 0.11 a 30.110.6 b 7.70.09 a

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63 Table 24 Mean total P, bulk density(BD), %LOI and pH values of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) and depth 05 cm and 510 cm depth. Treatment means within the same column followed by the same letter are not different by Tukeys test between depths for each canal. P = 0.05 ns not significant. Canal Depth cm Total P mg kg 1 BD g cm 3 %LOI pH 09A 0 5 794 a 0.19 b 31.8 ns 7.5 ns 09A 5 10 636 b 0.40 a 31.8 7.5 00A 0 5 1520 a 0.12 b 53.7 a 7.1 ns 00A 5 10 1130 b 0.20 a 45.6 b 7.3 06AB 0 5 575 ns 0.37 b 28.8 ns 7.7 ns 06AB 5 10 569 0.40 a 30.1 7.7

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64 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% T1 T2 T3 T4 T5 T1 T2 T3 T4 T5 T1 T2 T3 T4 T5 Farm Canal 00A Farm Canal 09A Farm Canal 06AB KCl P NaOH Pi NaOH Po HCl P Residue P Figure 22 Percent comparison of KCl P, NaOH Pi, NaOHPo, HClP and Residue P fractions at five transects (T1T5) at depth 05 cm in farm canal 00A, 09A and 06AB.

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65 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% T1 T2 T3 T4 T5 T1 T2 T3 T4 T5 T1 T2 T3 T4 T5 Farm Canal 00A Farm Canal 09A Farm Canal 06AB KCl P NaOH Pi NaOH Po HCl P Residue P Figure 23 Percent comparison of KCl P, NaOH Pi, NaOHPo, HClP and Residue P fractions at five transects (T1T5) at depth 510 cm in farm canal 00A, 09A and 06AB

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66 Table 25 KClP, NaOH Pi and NaOH Po fractions of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) at depths 05 cm and 5 10 cm. Transect KCl P (mg kg 1 ) NaOH Pi (mg kg 1 ) NaOH Po (mg kg 1 ) 09A 00A 06AB 09A 00A 06AB 09A 00A 06AB -----------------0 5 cm -----------T1 5.4 0 ns 29.9 ns 5.4 0 ns 121 ns 73 .4 ns 9.0 0 ns 180 ns 2 0.6 ns 18 .4 b T2 3.6 0 11 .2 4.6 0 83 .3 8 0.8 1 7.7 150 16.5 26.8 ab T3 7.8 0 18 .4 7 .0 0 32 .1 10 1 9.9 0 61 .6 10 1 28 .3 ab T4 11 .0 14.6 8.7 0 24 .3 6 4.7 14 .0 96 .4 4 3.9 39 .4 a T5 10 .4 1 1.5 11 .2 56 .0 52 .3 25 .2 12 3 8.1 4 24.7 ab ------------------5 10 cm -------------T1 11.7 ns 4.3 0 ns 4.6 0 ns 93 .2 ns 22 .1 c 9.2 0 ns 140 ns 4.3 0 ns 16 .3 bc T2 3.9 0 4.6 0 5.4 0 35.9 58.7 b 13 .0 50 .1 9.4 0 15 .3 c T3 2.6 0 1 4.7 5.9 0 31 .0 129 a 6.6 0 36 .1 42 .0 20 .2 abc T4 4.2 0 4.8 0 7.6 0 1 7.9 56.9 b 8.0 0 23 .1 2 0.5 28 .1 ab T5 11 .0 14 .2 5.6 0 38 .2 45 .4 bc 9.80 16 2 12 .4 3 1.6 a Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal and depth. P = 0.05 ns not significant

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67 Table 26 KClP, NaOH Pi, NaOHPo, of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) at depths 05 cm and 5 10 cm. Treatment means within the same column followed by the same letter are not different by Tukeys test between canals for each depth. P = 0.05 ns not significant. Table 27 Mean HClP and ResidueP of farm canals 00A, 09A and 06AB from transect 1(T1) to transect 5(T5) at depths 05 cm and 5 10 cm. Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal and depth. P = 0.05 ns not significant. Canal KCl P mg kg 1 NaOH Pi mg kg 1 NaOH Po mg kg 1 -----------------0 5 cm ----------------09A 7.643.17 b 63 .339.6 a 12045.9 a 00A 17 .1 .7 1 a 74.4 8 .2 a 38 .037.6 b 06AB 7.38 .6 5 b 15 .2 .6 0 b 2 7.5 64 b ------------------5 10 cm ----------------09A 6.68 .3 1 ns 43 .2 9 .0 a 82.363.9 a 00A 8.5 2 .4 2 62 .440.0 a 17.714.7 b 06AB 5.8 2 1 1 9.3 22.39 b 22 .3 .2 4 ab Transect HCl P (mg kg 1 ) Residue P(mg kg 1 ) 09A 00A 06AB 09A 00A 06AB -------------------0 5 cm ---------------T1 521 ns 589 ab 245 ns 293 ns 342 ns 111 c T2 422 723 ab 305 273 426 162 abc T3 50 4 1210 a 401 162 515 140 bc T4 379 658 ab 344 158 433 205 ab T5 385 603 b 296 239 514 247 a -------------------5 10 cm -----------------T1 402 ns 232 c 355 ns 211 ns 200 b 131 b T2 328 506 b 308 192 321 ab 121 b T3 412 1130 a 31 5 108 556 a 122 b T4 322 544 ab 309 167 395 a 182 ab T5 359 477 bc 332 151 351 ab 257 a

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68 Tab le 2 8 HClP and ResidueP of farm canals 00A, 09A and 06AB from transect1(T1) to transect 5(T5) at depths 05 cm and 510 cm. Treatment means within the same column followed by the same letter are not different by Tukeys test between canals for each depth. P = 0.05 ns not significant. Table 29 Correlation between sediment BD, %LOI, pH and Total P. Significant at the 0.0001 probability level Canal HCl P mg kg 1 Residue P mg kg 1 ----------------0 5 cm ----------------09A 442 66.6 b 225 62.6 b 00A 756257 a 446 72.1 a 06AB 318 58.2 c 173 53.8 b ----------------5 10 cm ---------------09A 365 41.3 b 166 39.5 b 00A 578332 a 365129 a 06AB 324 20.3 b 163 58.4 b BD gm cm 3 %LOI pH Total P mg kg 1 BD 1.00* 0.74* 0.42* 0.62* LOI 0.74* 1.00* 0.44* 0.78* pH 0.42* 0.44* 1.00* 0.56* Total P 0.62* 0.78* 0.56* 1.00*

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69 CHAPTER 3 PHYSICOCHEMICAL CHARACTERISTICS AND PHOSPHORUS FRACTIONA TION OF THE EVERGLADES AG RICULTURAL AREA (EAA ) MAIN CANAL SEDIMEN TS 3.1 Introduction 3.1.1 Historical Background. The Everglades Agricultural Area (EAA) in South Florida, is situated south of the fresh water l ake Okeechobee and north of the Water Conservation Areas (WCAs). Soils in EAA are mostly H istosols (SFER 2010; Rice et al., 2002 ). Flat topography in the EAA (Bottcher and Izuno, 1994) and uneven distribution of rainfall (SFER 2010) makes drainage essential, which is accomplished through a network of canals and pumps. Agricultural drainage water is routed from field ditches through the farm canals into the main canals. Farm canals are individually owned and managed by growers, whereas main canals are operated and maintained by South Florida Water Management District (SFWMD). Four major main canals were originally dug in the early 1900s to drain part of the Everglades: Miami canal North New River canal Hillsboro canal and the West Palm Beach canal (Ligh t and Dineen, 1994). These canals were constructed by digging through the EAA limestone bedrock (Gleason and Spackman, 1974). Pumping stations in EAA main canals help direct water from the main canals into the WCAs. Pumps used in EAA farm canals are operat ed by farm growers and can be either manually driven or with automatic onoff level. Low capacity pumps in EAA farm canals can range from 18.932.3 m3 min1 while high capacity pumps can range between 22.7132.5 m3 min1 (SFER 2004). Pumps used in EAA m ain canals are managed by SFWMD and have higher discharge capacity. For example t he S 3 pump station located at lake Harbor on the southern l ake Okeechobee has three diesel powered pumps with a maximum discharge capacity of 4383.4 m3 min1. The S 135 pump station located northeast of

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70 l ake Okeechobee, has a discharge capacity of 849.5 m3 min1, and pump station G 370 situated on North New River canal has a discharge capacity of 4714 m3 min1The Everglades once a contiguous wetland was drained for flood control and agriculture through the construction of canals, levees and water control structures (Light and Dineen, 1994). Agriculture in EAA caused runoff enriched with nutrients (Snyder and Davidson, 1994). Due to years of agricultural practices P has been accumulating in EAA canal sediments. Phosphorus accumula ted in sediments can play a pivotal role in P cycling between sediment solid phase pools, and diss olved P (Mortimer, 1941; Stumm and Leckie, 1970). The P storage in canal sediments is much greater than that in canal water. As a consequence, small amounts o f P released from sediments can significantly impact water column P concentrations (Bostrom et al., 1982) thereby influencing water quality of the canals as well as the downstream ecosystems. Hence, to evaluate the potential impact of the EAA canal sediments on water quality it is essential to understand the mobility and reactivity of P stored in these sediments. Sediment P mobility and reactivity was assessed through the analysis of physicochemical properties, P fractionation, and sediment mineralogy. Drainage/runoff of the EAA is the main source of surface water inflow into the Everglades Protection Area (EPA), consisting of Arthur R. Marshall Loxahatchee National Wildlife Refuge, Water Conservation Areas (WCAs), and the Everglades National Park (ENP) (SFER, 2010). This phosphorus (P) enriched drainage water from the EAA has been cited as one of the main reasons of ecosystem changes in the WCAs and the ENP (LOTAC., 1990; Whalen et al., 1992).

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71 3.1. 2 Factors Affecting Sediment Properties in EAA Sediment transport and P distribution can be controlled by physicochemical properties such as, pH, total P, bulk density and organic matter content. Sediment P can be present in different forms that have different mobility and bioavailability. Thus to asse ss the potential of P mobility, internal P cycling, it is necessary to know the distribution of P among different sediment phases including reactive and recalcitrant forms (Olila et al., 1994). The mobility and reactivity of P in sediments is determined not only by different P forms but also by sediment mineral phases (Mortimer, 1941). Sediment P can be adsorbed onto Fe and Al oxyhydroxides, carbonates or can undergo precipitation or coprecipitation with Ca, Fe, and Al minerals (Mortimer, 1941; Stumm and Leckie, 1970; Jensen and Thamdrup, 1993). Predominance of a biogeochemical process in sediment P cycling is dependent on sediment mineralogy (Koch et al., 2001). Sediments dominated by mineral forms of calcium carbonates can be influenced by carbonate chemi cal equilibria in contrast to redox. Thus sediment mineralogy can also reveal important information about the predominant chemical process of these sediments. According to Hupfer and Lewandowski (2005), and Ahlgren et al. (2006), in addition to inorganic P the mobility and reactivity of organic P compounds can also influence the water quality of aquatic ecosystems. Organic P compounds can include a wide variety of compounds including phospholipids, nucleic acids, inositol phosphates, phosphoproteins, sugar phosphates, phosphonic acids, humic associated organic compounds, polyphosphates and pyrophosphates (McKelvie, 2005). These organic P compounds can differ in their degree of reactivity and degradability. High molecular weight organic phosphates like inosi tol phosphates or phytic acid are resistant (Bowman and Cole, 1978; Islam and Ahmed, 1973) and can be strongly adsorbed to the surfaces

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72 of ferric oxides (De Groot and Golterman, 1993). Under anaerobic conditions organic monoesters can degrade to orthophosp hate (Suzumura and Kamatani, 1995) and under alkaline environment, diesters can degrade to orthophosphate monoesters in as little as 24 h (Turner et al., 2003). 31P Nuclear Magnetic Resonance (NMR) spectroscopy has been used to identify organic P compounds in sediments (Sundareshwar et al., 2001; Hupfer et al., 2004; Ahlgren et al., 2006). Soil P fractionation in contrast to 31The Everglades is underlain by a central relativ ely impermeable limestone bedrock (Gleason and Stone, 1994) composed of deposits of calcium carbonate (CaCO P NMR spectroscopy does not provide structural information of P compounds present in soil extracts (Turner et al., 2003). The com position of P forms stored in the different EAA canals can differ from each other depending on the composition of particulate P from EAA drainage and geological factors affecting the mineralogy of sediments. 3) (Scott, 1997). As ancient sea levels receded the CaCO3 bedrock was formed as unconsolidated sand grains (Obeysekera et al., 1999). Carbonatic minerals could hence be an important part of EAA canal sediment mineralogy and can affect the physicochemical properties of sediments including pH, bulk density, total P and distribution of P fractions. The majority of the EAA bedrock is composed of the Fort Thompson Formation (USGS, Figure 3.1) except in the eastern part where bedrock Anastasia Formation overlies the Fort Thompson Formation. The Fort Thompson Formation is composed of interposed layers of muddy sand with beds of shells in a quartz and sand m atrix (Petuch and Roberts, 2007) The Anastasia formation is composed of seashell fragments, quartz and sand, calcium carbonate and iron oxide

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73 (Monk et al., 1968). The configuration of the EAA bedrock is irregular. The western part of the EAA is topographi cally higher known as the West Everglades High, while the eastern part is the relatively low lying Loxahatchee Channel (Gleason et al., 1974). The high bedrock topography in southwest EAA and in the lower eastern part of EAA may lead to dominant mineral pr operties in sediments. We hypothesized that (i) physicochemical properties of EAA main canal sediments would vary within a canal and between the canals and, (ii) canal sediments would differ with respect to different P fractions and mineralogical compositi on. The objectives of this study were to determine: (i) the sediment physicochemical properties (ii) the P fractions and mineralogical composition within EAA main canals. The results were compared within different transects in canals as well as between the canals. 3.2 Materials and M ethods 3.2.1 Description of Main Canals Sediments were collected from three different main/district canals: Miami canal situated in the western part of EAA; West Palm Beach canal (WPB) situated in the eastern EAA ; and the Ocean canal situated in the southeastern EAA. The main canals are managed by the SFWMD, thus they are also called the district canals. The EAA mail canals facilitate runoff removal and also supply irri gation water to the farms (SFER 2009). The EAA main c anals have their origin in l ake Okeechobee and drain through several farms before ultimately flowing into Atlantic Ocean. Drainage water in EAA farms is routed through farm canals into main canals with gated control structures. The flow of agricultural drainage water is from the farm canals, to the main canals, the Storm

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74 Treatment Areas (STAs), Water Conservation Areas (WCAs) and Everglades National Park (ENP). Miami canal also known as the C 6 canal has its source at S 3 pump station on l ake Okeechobee ranges about 85 miles (13600 m) to Miami River that ultimately drains into B iscayne Bay to the south (SDAMP 2001). This canal passes through Palm Beach, Broward and Dade counties, the EAA, WCA 3, the Everglades and overlies the Fort Thomson formation. The Mi ami canal carries EAA runoff to Holeyland Wildlife Management Area and WCA 3. Gated water control structures S 339 and S 340, transmit water from the canal into WCAs. The West Palm Beach canal also known as C 51 canal overlies the Fort Thomson formation and stretches 42 mil es (67600 m) from canal point, l ake Okeechobee and flows southeast to Twenty Mile Bend (SDAMP 1999). The stretch of WPB canal ,until Twenty Mile Bend provides drainage in EAA S ubsequently it flows to the northern boundary of Arthur R. Marshal Loxahatchee National Wildlife Refuge. Thereafter the L8, L 40 and L7 canals drain into the WPB canal. Further eastward WPB canal receives stormwater runoff from the coastal urban area from the cities of Royal Palm Beach, Haverhill, Wellingto n and Palm Springs, the Acme Drainage District, Indian Trail Improvement District, and the l ake Worth Drainage District. After passing through the south side of the Palm Beach International Airport, the WPB canal first turns south and then to the east into the l ake Worth Lagoon. The Ocean canal is about 21000 m long, and is a connecting canal that connects main canals Hillsboro canal and WPB canals, both of which origi nate from l ake Okeechobee (SFER 2009). At Twenty Mile Bend the Ocean canal joins the WPB canal

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75 (SDAMP 1999). Ocean canal stretches east west and overlies the Fort Thomson and the Anastasia bedrock formation. 3.2.2 Sediment Sampling Sediment cores were collected from four different transects from the three main canals (Figures 32, 3 3, 3 4). The first transect (T1) for Miami and West Palm Beach canal was closest to the lake while the other transects (T2T4) were taken progressively southward into the EAA. For Ocean canal T1 was closest to WPB canal Triplicate sediment cores were collected at each transect within the middle two thirds of the canal crosssectional area. Transect locations at each study site were marked by GPS coordinat es using a Trimble Unit Pro XR DGPS Unit (Trimble Navigation Limited Mapping and GIS Systems, Sunnyvale, CA). At each transect two steel rebars were installed at the edge of the water on each side of the canal. During sediment sampling, a steel cable was a ttached to the anchor rebars to anchor a boat used during measurements. Triplicate sediment cores were collected at each transect within the middle two thirds of the canal crosssectional area. The sediment cores were transported upright to the laboratory, stored at 4oC and sectioned within 24 h. The water in the columns was removed by vacuum suction, and the sediment sectioned at depth 0 to 5 cm. Sediment samples were stored in plastic jars and stored at 4o3.2.3 Sediment Analysis C until analysis. 3.2.3.1 Physicochemical properties All samples were analyzed for moisture content, bulk density, organic matter, and total P. Organic matter content was determined by igniting an ovendried sediment sample at 550oC for 4 h in a muffle furnace (Andersen, 1974). The residue following

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76 digestion of the ash was analyzed for total P using the ascorbic acid method (Method 365.4, U.S. Environmental Protection Agency, 1983). 3.2.3.2 Phosphorus fractions The distribution of P in the canal sediments of the EAA were determined by the sequential chemical fractionation procedure followed by Reddy et al. (1995 and 1998). The operationally defined scheme was composed of five steps: (i) KCl extractable P: This fraction represents the labile Pi that is water soluble and exchangeable (loosely adsorbed); (ii) NaOH extractable P: This fraction is considered to represent the Feand Al bound P and humic and fulvic acids (P bound to Al, Fe oxides and hydroxides; (iii) HCl extractable P: This frac tion represents the Caand Mg bound P; (iv) alkali extractable organic P (fulvic and humic bound P); and (v) residual P: This fraction is thought to represent recalcitrant organic P compounds and P bound to minerals. Field wet samples (0.3 g dry weight equivalent, were sequentially extracted with 1 M KCl (labile P), 0.1 M NaOH (Fe and Al bound P, and alkali extractable Po), and 0.5 M HCl (Ca and Mg bound P). The data for each P fraction from each canal were evaluated transect wise averaging the replic ates of each transect. (The details of the fractionation procedure are provided in the Appendix A ). 3.2.3.3 Thermogravimetry Organic matter content was determined by igniting sediment sample at 550oC for 4 h in a muffle furnace (Andersen, 1974). This method is based on the principle that, at the chosen temperature, all organic carbon is converted to CO2, where loss of CO2 from carbonates and loss of water from clay minerals are negligible. For calcareous EAA sediments this assumption can lead to erroneous r esults which can be avoided by thermogravimety (TG). In a thermogravimetric analysis, a substance is subjected to a

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77 controlled temperature while the change in mass of the substance is recorded as a function of temperature (Earnest, 1988). Thermogravimetric measurements are carried out in air or in inert gas atmosphere, such as helium (He) or argon (Ar) using a computer controlled thermal analysis system. In addition, TG can also provide information on the quantity of the minerals, for example calcite and dolomite present in the sediments. Estimates of organic matter content by TG method can be drawn by the wei ght loss between approximately 200 and 600oC depending upon the TG curve inflections (Harris et al., 2007). Minerals like 1:1 layer silicates Kaolinite and Halloysite have weight losses from 400oC to 600oC (Jackson, 1975) while 2:1 layer silicates like Mg smectite have weight loses at 25250oC (Karathanasis and Hajek, 1982) and at 600900oC (Jackson, 1975). 2:2 layer silicates like chlorite have weight l osses in the range 540800o3.2.3.4 X r ay d iffraction (XRD) C (Jackson, 1975). The canal sediments were mixed thoroughly with a spatula and a portion of it was transferred in to a sieve (mesh size #270) placed on a funnel over a 1000 mL beaker. The contents were stirred using a rubber policeman and distilled water. The silt and clay size portions (<50 ) were collected into the glass beaker while the sand fraction was left on the sieve. This process was continued until the leachate was c olorless. About 50 m L of the silt and clay solution was filtered by vacuum suction using 0.45 filter paper. The contents collected on the filter paper were first rinsed wi th distilled water followed by m agnesium chloride (MgCl2) solution for m agnesium saturation. The layers were cation saturated (Mg) to aid in identification of phyllosilicates (Whittig and Allardice, 1986). Distilled water was used to get rid of excess MgCl2. Excess moisture was

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78 removed and the thin layer of silt and clay was mounted onto a labeled glass slide and sto red in water desiccators for X r ay analysis. The X ray diffractometer was equipped with graphitecrystal monochromator. X r ay analyses of the samples were done at a scan rate of 2o3.2.3.5 31Extracts f or P NMR 31P NMR analysis were prepared by shaking 5 g of wet sediment containing 0.25 M NaOH and 0.05 M EDTA for 4 h at 20oC (Cade Menun and Preston, 1996) and centrifuging the contents at 10,000 rpm for 30 min. Equal volumes of the replicate extracts were combined and frozen immediately at 80oC. The frozen extracts were lyophilized, ground and stored in the refrigerator. Lyophilization or freezedrying works by freezing the material and reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to gas. Prior to analysis the freezedried samples were redissolved in 0.9 mL solution of 1 M NaOH and 0.1 M EDTA. About 0.1 mL of deuterium oxide was added to the mixture and transfer red to a 5mm NMR tube. The deuterium oxide acts as an NMR signal lock by providing temporally constant and homogenous magnetic field necessary to produce a high resolution NMR spectrum. Solution 31P NMR spectra was obtained using a Mercury 300 MHz spectro meter using a 6s pulse (45o), a delay time of 1.0 s, an acquisition tim e of 0.2 s, and between 48,000 and 69,000 scans. Chemical shifts of signals were expressed in parts per million (ppm), relative to an external standard of 85% H3PO43.2.4 Statistical Data Analysis and Methylene DiPhosphonic Acid (MDPA) as the internal standard. Descriptive statistics of means, standard deviation, and standard errors (proc MEANS), were performed on data collected from the sediment sample analysis using

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79 SAS statistical p rogram (SAS Institute, 2003). Normality and goodness of fit tests were conducted to check the distribution patterns of the physicochemical properties and P fractions. Where the data were not normally distributed, log transformations were used to stabilize the variance, and make the residuals Gaussian distributed for parametric analysis. Analysis of variance (ANOVA) was used to compare sediment physicochemical properties and P fractions between canal transects (USEPA., 1983, 1989). Summary statistics were conducted and Tukey test were used (SAS Institute, 1999) to assess significant differences between P forms, transects, and canals. 3.3 Results and Discussion 3.3.1 Physicochemical Properties Sediment total P varied from 914 mg kg1 at T3 to 1938 mg kg1 at T4 in Miami canal (Table 31). Miami canal T4 had the greatest total P value among all the canals. Studies of six EAA canal sediments by Anderson and Hutcheon (1992) also showed that total P of Miami canal was the greatest Total P values for WPB canal did not vary significantly along transects and average total P for WPB canal was 1134 mg kg1. Total P values for Ocean canal varied from 432 mg kg1 at T1 to 932 mg kg1Bulk density values for Miami canal sediments varied from 0.14 g cm at T4. Miami and WPB canal had higher total P values than Ocean canal (Table 32). O cean canal is a connecting canal that drains lesser area than either West Palm Beach canal or Miami canal (Figure 2 2) that can lead to lower drainage from farm canals and thus low total P values. 3 at T3 to 0.54 g cm3 at T4 (Table 31). Miami canal T4 had the greatest bulk density among all transects and all main canals. Bulk densities of WPB canal varied from 0.12 g cm3 at T3 to 0.29 g cm3 at T2. Bulk density values of Ocean canal did not vary significantly

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80 between the different transects and averaged around 0.35 g cm3Sediment %LOI values in Miami canal ranged from 7.19% at T4 to 42.9% at T2 (Table 33). Miami canal T4 had the smaller %LOI value at all the transects and all the canals than WPB and Ocean canal The %LOI values for WPB canal did not vary significantly between the transects and averaged about 26.7%. For Ocean canal sediments the %LOI varied from 17.4% at T3 to 37.6% at T4. The %LOI values did not vary significantly among Miami, WPB and Ocean canals (Table 34). Ocean canal sediments had higher bulk density values than either Miami or WPB canal (Table 32). The pH values of Miami canal ranged from 7.2 at T2 to 7.7 at T4 (Table 33). The pH value at T4 was the greatest amon g the transects of Miami canal, while there was no statistical difference between the pH values of the rest of three transects. The pH values of WPB canal did not change significantly between the transects and averaged about 7.4. Ocean canal sediment pH values varied from 7.8 at T4 to 7.9 at T2 and T3. Among the canals Ocean canal sediments had higher pH values than both Miami and Ocean canal (Table 34). Everglades Agricultural Area main canals were constructed by dredging down to the limestone bedrock (St uck, 1996). Sediment trapping experiments by Hutcheon engineers (1995) showed that sedimentation at canal bottom occurs at the rate of 42.754.9 cm yr1. Therefore EAA canal sediment properties are influenced both by limestone bedrock properties and partic ulate materials deposited. The source of particulates in canals can be soil mobilized from farms (Stuck, 1996) or from in canal biological growth (Daroub, 2002a ). High total P values of Miami and WPB canal could be due to high total P of materials deposite d. Higher bedrock topography at Ocean canal has possibly

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81 influenced the sediment physicochemical properties which results in lower total P, higher bulk density, lower %LOI and higher pH. The shallow depth of Ocean canal has possibly further facilitated the transport of flocculent particulate matter leaving behind materials that is highly mineral in nature. 3.3.2 Phosphorus Fractions of EAA Main Canal Sediments The KCl Pi fraction represented 0.22% of the total P in surface sediments at all the transects in the main canals (Figure 33). The KCl Pi fraction did not vary significantly between the different transects of Miami and WPB canal and averaged around 7. 7 8 and 14.2 mg kg1. Ocean canal KCl Pi (Table 3 5) values ranged from 4.52 7.9 1 mg kg1Inorganic NaOH Pi ranged from 38% of the total P in all main canal sediments. The values of NaOH Pi did not vary significantly among the different transects of the main canals and averaged 105 mg kg KClPi valu es did not vary significantly between the canals (Table 36). 1, 93. 2 mg kg1 and 18.1 mg kg1The NaOH Po fraction represented 16% of total P in all canal sediments. The NaOHPo values did not vary significantly between the different transects of the Miami, WPB and Ocean canals and averaged 88. 2 49.4 and 4. 18 mg kg for Miami, WPB and Ocean canal respectively (Table 36). The significance of NaOH Pi fraction is its susceptibility to changes with redox potential that can result in possible long term P release to the water column. Phosphorus stored as Al bound P is relatively stable, but Fe bound P is strongly affected by sediment physicochemical properties such as changes in redox potential. The reduced form of Fe is more soluble than its oxidized counterpart, thus, P release from sediments is normally greater under anaerobic conditions (Hieltjes and Lijklema, 1980; Olila et al., 1995). NaOH Pi values of Miami canal and WPB canal were higher than Ocean canal. 1 (Table 36). Under

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82 oxygen deficient conditions, NaOH Po pool is relatively stable as the rate of organic matter decomposition is regulated by the availability of oxygen. Sediment NaOH Po values of Miami and WPB canal were higher than Ocean canal sediments (Table 36). The HClPi fraction at all canals accounted for 6073% of total P in the surface layer sediments of the main canals, and was the largest P fraction at all the transects of all canals. The HCl Pi values for Miami canal ranged from 653 mg kg1 at T1 to 1530 mg kg1 at T4. Sediment HCl Pi values did not vary significantly between transects of WPB canal and average HCl Pi value was 649 mg kg1 (Table 37). Ocean canal HCl Pi values ranged from 316 at T2 to 735 mg kg1Residue P fraction was the second largest storage pool, after the HCl Pi pool. Sediment residue P at all transects represented about 1726% of total P. Residue P values for WPB canal varied from 187 mg kg at T4. Ocean canal T4 had the greatest HClP while the values did not vary significantly between the rest of the transects. The HClP values of Miami and WPB canal were greater than Ocean canal (Table 38). 1 at T2 to 389 mg kg 1 at T3 (Table 37). The values of residueP did not vary significantly among transects of Miami and Ocean canal and averaged 234 and 127 mg kg13.3.3 Thermogravimetry and X R ay Diffraction respectively. Miami and WPB canal sediments had higher residue P values than Ocean canal sediments (Table 38). The m ineralogical composition of the EAA canal sediments was studied by TG and XRD. Thermogravimetric studies on sediment samples of Miami canal T1T3 indicated four inflections corresponding to weight loss due to moisture, organic matter, dolomite and calcite (Figure 34). Temperature range for weight loss due to organic matter was approximately between 300 and 600oC depending on the inflection of the curve. Thermogravimetric analysis for sediments from T4 of Miami canal resulted in 3

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83 inflections corresponding to weight loss due to moisture, organic matter and calc ite. The %Wt loss due to OM in T4 of Miami canal was smallest in all transects and canals (Figure 3 4), this was also observed in the %LOI values. Thermogravimetric curves of sediment samples from WPB canal showed four inflection points corresponding to weight loss due to moisture, organic matter, dolomite and calcite. Similar to Miami canal T1, T2 and T3 and WPB canal sediments, Ocean canal sediments showed four inflections signifying weight loss due to moisture, organic matter, dolomite (DO) and calcite ( CO) Sediment weight loss in all the transects and canals followed the trend %Wt loss OM > %Wt loss CA > %Wt loss DO. The %Wt loss OM for Miami and WPB canal higher than Ocean canal sediments as observed in the %LOI values from the analysis of physicochemi cal properties. Along with having smaller %Wt loss OM values than other Miami and WPB canal the %Wt loss CA for Ocean canal sediments is greatest (except for Miami canal T4) among all the three canals which suggest that Ocean canal sediments are more mineral in nature than either Miami canal and WPB canal sediments. The presence of dolomite [(CaMg(CO3)2] was confirmed by XRD studies in sediment samples from T1T3 but dolomite was not found in T4 (Figure 35). Miami canal sediment samples from T1T3 had similar mineralogical composition. Other minerals identified by XRD in Miami canal samples were sepiolite (Mg silicate), quartz, calcite (CaCO3), and aragonite (polymorph of calcite). The heights of the peaks of calcite and aragonite from Miami canal T4 su ggested that this transect contained higher concentration of calcite and aragonite than the other transects. Mineralogical compositions of sediment samples from Miami canal T1T3 were very similar to those of

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84 l ake Okeechobee mud sediments determined by Har ris et al. (2007). Obeysekera et al. (1999) indicated that mineral matter from l ake Okeechobee could be washed into the canals, which explains the similarity in mineralogical composition between Okeechobee and EAA canal sediments. X r ay d iffraction studies after oxidation of organic matter and removal of carbonates from clay suspensions from Miami canal sediments indicate the presence of smectite and kaolinite in these sediments (Table 39). Mineralogical composition determined by XRD on WPB canal verified the presence of dolomite, calcite along with sepiolite and quartz in the sediments (Figure 36). In contrast to Miami canal, the four transects of WPB canal were mineralogically similar. X ray d iffraction studies after removal of organic matter and carbonates determined the presence of smectite, palygorskite (magnesium aluminum phyllosilicate) and kaolinite in the sediment samples of WPB canal (Table 310). The XRD data of Ocean canal sediments indicated the presence of palygorskite in addition to sepiolite, calcite, dolomite, quartz and aragonite (Figure 37). The presence of phyllosilicates like smectite and kaolinite was verified after removal of organic matter and carbonates from sediment clay suspensions (Table 311). Minerals like smectite, sepiolite, and palygorskite foun d in the EAA canal sediments lose water in the temperature range of 105 and 550oC. Thus weight loss due to organic matter determined by TG in the 300600oMineral ogical studies of EAA canal sediments are lacking but the nature of Florida Bay sediments were studied by Scholl (1966) whereby he concluded that these sediments consisted mostly of calcium carbonate. The major components of Florida Bay sediments were foun d to be mollusk shells (Ginsburg, 1956), aragonite, sponge C range cannot be solely attributed to organic matter in these sediments.

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85 spicules (Stockman et al., 1967). X r ay d iffraction s tudies on the clay fraction of l ake Okeechobee indicated the presence of smectite, sepiolite, quartz, calcite and dolomite while the fine silt f r action of l ake Okeechobee indicated the presence of quartz along with calcite and dolomite (Harris et al., 2007). The current study in the EAA main canal sediments revealed that all three canals were dominated by carbonate minerals which is consistent wit h the geology of the area. The Fort Thomson bedrock formation that underlies Miami and WPB canal, and Anastasia formation that underlies Ocean canal is composed of sand, shells and quartz. Visual assessment of the sediments, particularly Ocean canal sedime nts revealed an abundance of intact and broken seashells. The higher quantity of calcite in T4 of Miami canal could be attributed to higher bedrock topography in southwestern EAA. All the three main canals indicated the presence of sepiolite, quartz, calci te and dolomite. In addition aragonite was found in Miami canal and palygorskite in WPB and Ocean canal Sepiolite and palygorskite found in EAA main canals, owing to small particle size, low density and fibrous nature could be easily resuspended in the water column of the canals (Harris et al., 2007). This is important as flow conditions in EAA main canals are regularly managed, and the turbulence can cause these minerals to resuspend and flow to the downstream ecosystems. The lack of crystalline forms of Ca P minerals was probably due to the inhibition in mineral formation by the presence of carbonates (Stumm and Leckie, 1970), organic acids (Inskeep and Silvertooth, 1988), absence of seed crystals (Griffin and Jurinak, 1973). Phosphate has been shown to be adsorbed on calcite and aragonite surfaces (Griffin and Jurinak, 1973; Kitano et al., 1978; Millero et al., 2001). Thus it is likely that P in Miami, WPB and Ocean canals do not exist as discrete phosphatic minerals but exist

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86 as adsorbed phosphate on car bonate minerals. This is supported by the fact that deposits of P mineral s occur in central and northern Florida but have not been found in south Florida (Porter and Porter, 1997). Consequently it was suggested by Noe et al. 2001 that P fr om weathering of mineral rock is not available in the Everglades. 3.3.4 31P NMR A nalysis 31The NMR study on the canal sediments yielded orthophosphate as the only detectable P compound, apart from the internal standard MD PA. The inability to find org anic P forms may be due to the low organic P (NaOH Po) concentrations in the main canal sediments suggested by the P fractionation study Phosphorus sequestration and litter decomposition in the WCAs have been thought to be responsible for the P NMR analysis was performed on the sediments of the main canals to determine the nature of organic P compounds present in the sediments. The analyses were performed on 0.25 M NaOH and 0.05 M EDTA (ethylene diamine tetra acetate) extracts of the sediments, using MDPA (methyl di phosphonic acid) as the internal standard. The NaOH EDTA extraction has been applied to samples from the Florida Everglades (Robinson et al., 1998; Pant et al 2002; Turner et al., 2006; Turner et al., 2007). Robinson et al. (1998) identified inorganic ortho P, ortho P monoester, and ortho P diester in the organic soils of Apopka marsh, Eustis Much Farm and Sunny Hill Farm. Pant and Reddy (2001) analyzed the d etrital matter as part of the Everglades Nutrient Removal Project (ENRP) and identified P compounds like sugar phosphate, glycerophosphates, polynucleotides and phospholipids. Turner and Newman (2005) identified the presence of inorganic phosphate, phosphate monoesters, DNA and pyrophosphates in sites dominated by cattail and sawgrass in WCA 1 and 2.

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87 identificati on of organic P compounds like phosphodiesters and pyrophosphates (Cheesman et al., 2010) 3.4 Conclusions The physicochemical properties, P fractions and mineralogy of the sediments varied with transect and canals. The physicochemical properties of Miami WPB canal sediments were similar in terms of total P, bulk density, %LOI and pH. In addition to high total P, both Miami and WPB canal sediments had low bulk densities which make them susceptible to resuspension and downstream transport. This is a cause of concern due to the high total P content of these sediments. Miami canal T4 was very different compared to the three other transects in terms of very high total P, high bulk density, high pH and very low %LOI. Physicochemical properties of Ocean canal sediments were very different from Miami and WPB canal sediments. Ocean canal sediments had lower total P, higher bulk density and higher pH values than Miami and Ocean canal. Ocean canal sediments were more mineral in nature compared to both Miami and WPB c anal. This could be due to the different bedrock formation underlying Ocean canal and the shallow canal depth. Shallow canal depth can mobilize sediments in lesser time than at deeper canals. This ease of mobilization prevents accumulation of particulate m atter contributing to increased mineral nature of Ocean canal. Phosphorus fractionation of main canal sediments indicated that HCl P or P associated with Ca and Mg was the dominant P fraction in all canals and transects. Mineralogical analyses did not indi cate the presence of apatite minerals which suggests that P is probably associated as adsorbed complexes on minerals phases.

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88 The second largest P fraction was residue P in all the canals and transects. Phosphorus from HCl P and residue is relatively unavai lable under canal conditions. The combined labile P, NaOH Pi and NaOH Po for Miami and WPB canal was higher than Ocean canal. This indicates that P release from Miami and WPB canal sediments would possibly be greater than Ocean canal sediments. X Ray Diffr action studies indicated that the dominant crystalline phase in all the main canals was calcite and polymorphs of calcite. Other minerals identified in the canal sediments were quartz, smectite, kaolinite, sepiolite and palygorskite. Sepiolite and palygors kite due to their fibrous nature and light weight can be easily suspended in the canal water column and be transported as suspended load. Canals with higher bedrock topography in EAA are likely to have lower canal depth where particulates more likely to be transported downstream resulting in dominant mineral properties in sediments including higher BD, higher pH, lower %LOI, lower total P, higher CaMg P and vice versa. The origin of particulate P in canals can be from in canal biological growth or due to s oil erosion from EAA farms. Similarity of min erals found in EAA canals with l ake sediments suggest s that particulate materials are transported down from the l ake to these canals. The EAA canal P fractions indicate that P can be released from these sediment s and thus it is necessary to perform research to determine the P release potential from these sediments which can affect water quality in the canals as well as in the downstream ecosystems.

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89 Figure 31 Different bedrock lay ers underlying EAA soils (USGS maps).

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90 Figure 32 Position of EAA main canals and the sampling transects within the main canals. Table 31 Mean total P and bulk density of Miami, WPB and Ocean canal sediments from T1 to T4. Transect Total P (mg kg 1 ) Bulk Density (g cm 3 ) Miami WPB Ocean Miami WPB Ocean -----------0 5 cm ---------T1 1140 bc 1300 ns 481 ab 0.18 b 0.22 a 0.37 ns T2 914 c 11 90 432 b 0.18 b 0.12 b 0.36 T3 1730 ab 1010 514 ab 0.14 b 0.29 a 0.40 T4 1940 a 1050 932 a 0.54 a 0.26 a 0.26 -----------5 10 cm ---------T1 1240 a 953 ns 393 ns 0.18 b 0.30 ab 0.45 a T2 868 b 931 445 0.21 b 0.38 a 0.53 a T3 2050 a 1070 355 0.19 b 0.23 b 0.37 ab T4 886 b 1010 445 0.50 a 0.25 ab 0.20 b

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91 Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal. P = 0.05. ns not significant. Table 32 Mean total P and bulk density (BD) of Miami, WPB and Ocean canal sediments. Treatment means within the same column followed by the same letter are not different by Tukeys test between canals. P = 0.05. ns not significant. Table 33 Mean %LOI and pH values of Miami, WPB and Ocean canal sediments from T1 to T4. Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal. P = 0.05. ns not significant. Canal Total P mg kg 1 BD g cm 3 -----------0 5 cm ---------Miami 1430 a 0.26 b WPB 1130 a 0.22 b Ocean 590 b 0.35 a -----------5 10 cm ---------Miami 1260 a 0.27 b WPB 990 a 0.29 b Ocean 409 b 0.39 a Transect %LOI pH Miami WPB Ocean Miami WPB Ocean -----------0 5 cm ---------T1 30.1 a 28.9 ns 23.1 ab 7. 2 b 7. 3 ns 7.9 a T2 42.9 a 33.4 19.9 ab 7.3 b 7.4 7.9 a T3 24.3 a 18.4 17.4 b 7. 4 b 7.4 7.9 a T4 7.19 b 26.1 37.6 a 7.7 a 7. 4 7.8 b -----------5 10 cm ---------T1 26.7 a 41.0 ns 28.9 ns 7. 3 b 7.4 ns 8.0 a T2 37.2 a 24.4 17.4 7. 4 b 7.5 8.0 a T3 26.7 a 25.1 43.0 7. 5 b 7. 3 7.9 a T4 7.2 0 b 29.4 54.0 7.9 a 7. 5 7. 8 b

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92 Table 34 Mean %LOI and pH of Miami, WPB and Ocean canal sediments Treatment means within the same column followed by the same letter are not different by Tukeys test between canals. P = 0.05. ns not significant. C anal %LOI pH -----------0 5 cm ---------Miami 26.1 ns 7.4 b WPB 26.7 7.4 b Ocean 24.5 7.9 a -----------5 10 cm ---------Miami 24.4 b 7.5 b WPB 30.0 a 7.4 b Ocean 35.8 a 7.9 a

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93 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4 Miami WPB Ocean KCl P NaOH Pi NaOH Po HCl P Residue P Figure 33 Percent comparison of different P fractions from T1 to T4 in Miami, WPB and Ocean canal at depth 0 5 cm.

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94 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4 Miami WPB Ocean KCl P NaOH Pi NaOH Po HCl P Residue P Figure 34 Percent comparison of different P fractions from T1 to T4 in Miami, WPB and Ocean canal at depth 510 cm.

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95 Table 35 Mean labile P, NaOHPi and NaOH Po fra ctions of Miami, WPB and Ocean canal sediments from T1 to T4. Transect KCl P (mg kg 1 ) NaOH Pi (mg kg 1 ) NaOH Po (mg kg 1 ) Miami WPB Ocean Miami WPB Ocean Miami WPB Ocean -----------0 5 cm ---------T1 7. 27 ns 21 .1 n s 4.5 2 ns 22 6 ns 1 09 ns 1 6.5 ns 190 ns 7 5.9 n s 5.08 ns T2 6.8 2 15 .1 6.4 1 75 .4 1 30 17 .4 97 .4 44 .4 3.95 T3 6.4 1 9.9 0 6.9 0 74 .2 6 0.6 19 .2 36 .2 28 .2 3.81 T4 1 0.6 1 0.5 7.9 1 46 .3 73 .1 19 .2 29 .3 49 .2 3.89 -----------5 10 cm ---------T1 1 2.9 ab 11 .3 n s 5.0 0 ns 3 0.7 b 8 4.8 ns 12 .2 ns 1 2.6 ns 180 a 2. 57 T2 1 1.6 b 9.4 1 6.1 0 51 .0 ab 7 4.7 9. 07 3 2.6 65 .4 a 1. 57 T3 1 0.8 b 10 .2 1 2.7 110 a 120 18 .0 10 2 73 .2 a 1. 69 T4 2 5.5 a 4.1 0 9.7 0 77 .0 ab 19 .4 16 .1 32 .4 1 7 .1 b 2.8 4 Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal. P = 0.05. ns not significant.

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96 Table 36 Mean KCl P, NaOH Pi and NaOH Po of Miami, WPB and Ocean canal sediments. Treatment means within the same column followed by the same letter are not different by Tukeys test between canals. P = 0.05. ns not significant. Table 37 Mean HClP and Residue P fractions of Miami, WPB and Ocean canal from T1 to T4. Transect HClP (mg kg1) ResidueP (mg kg1) Miami WPB Ocean Miami WPB Ocean -----------0 5 cm ---------T1 653 b 790 ns 323 b 323 ns 137 ab 133 ns T2 589 b 649 316 b 206 389 a 101 T3 1140 a 571 323 b 269 187 b 106 T4 1530 a 585 735 a 138 217 ab 167 -----------5 10 cm ---------T1 447 ns 785 ab 250 ns 147 c 336 a 117 ns T2 590 587 b 288 180 bc 155 bc 56.9 T3 685 1280 a 170 351 a 233 ab 77.8 T4 648 794 ab 291 238 ab 92.5 c 128 Treatment means within the same column followed by the same letter are not different by Tukeys test between transects for each canal. P = 0.05. ns not significant. Canal KCl P mg kg 1 NaOH Pi mg kg 1 NaOH Po mg kg 1 -----------0 5 cm ---------Miami 7. 7 8 ns 10 5 a 88.2 a WPB 14 .2 93.2 a 49 .4 a Ocean 6.4 4 18.1 b 4. 18 b -----------5 10 cm ---------Miami 15 .2 a 6 7.2 a 4 4.9 a WPB 8.7 5 b 74 .7 a 8 3.9 a Ocean 8. 37 b 1 3.8 b 2. 16 b

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97 Table 38 Mean HClP and ResidueP of Miami, WPB and Ocean canal sediments. Treatment means within the same column followed by the same letter are not different by Tukeys test between canals. P = 0.05. ns not significant. 0 10 20 30 40 T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4 Miami WPB Ocean Percent Weight Loss (%W %Wt loss-OM %Wt loss-DO %Wt loss-CA Percent Wt loss (%Wt loss) Figure 35 Weight loss due to OM, Dolomite and Calcite of Miami, WPB and Ocean canal sediments from T1 to T4. Canal HCl P mg kg 1 Residue P mg kg 1 -----------0 5 cm ---------Miami 973 a 234 a WPB 649 a 232 a Ocean 424 b 127 b -----------5 10 cm ---------Miami 593 b 229 a WPB 863 a 204 a Ocean 249 c 95.0 b

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98 10 20 30 40 50 T1 CA AR QZ AR CA QZ SP AR CA AR CA CA AR CA AR DO T2 T3 T4 SP Figure 36 X ray d iffraction patterns from Miami canal sediments from T1 to T4. Table 39 Minerals identified in sediments of Miami canal sediments from T1 to T4. Canal Transect Minerals SP QZ CA DO AR SM KL PL Miami T1 T2 T3 T4 SPSepioliteMagnesium Silicate [Mg4Si6O15(OH)2 6H2O)] QZ Quartz Silicon dioxide (SiO2) CA Calcite Calcium carbonate (CaCO3) DO Dolomite Calcium magnesium carbonate,[CaMg(CO3)2] AR AragonitePolymorph of calcium carbonate, (CaCO3) SM Smectite (determined by removing carbonate and organic matter) KL Kaolinite (determined by removing carbonate and organic matter) PL Palygorski te Magnesium Aluminium Phyllosilicate (Mg,Al)2Si4O10(OH)4(H2O) (determined by removing carbonate and organic matter).

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99 10 20 30 40 50 T1 T2 T3 T4 CA DO QZ QZ SP SP CA CA CA Figure 37 X ray d iffraction patterns from WPB canal sediments T1 to T4. Table 310. Minerals identified in sediments of WPB canal sediments from T1 to T4. Canal Transect Minerals SP QZ CA DO AR SM KL PL WPB T1 T2 T3 T4 SPSepioliteMagnesium Silicate [Mg4Si6O15(OH)2 6H2O)] QZ Quartz Silicon dioxide (SiO2) CA Calcite Calcium carbonate (CaCO3) DO Dolomite Calcium magnesium carbonate,[CaMg(CO3)2] AR AragonitePolymorph of calcium carbonate, (CaCO3) SM Smectite (determined by removing carbonate and organic matter) KL Kaolinite (determined by removing carbonate and organic matter) PL Palygorskite Magnesium Aluminium Phyllosilicate (Mg,Al)2Si4O10(OH)4(H2O) (determined by removing carbonate and organic matter).

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100 10 20 30 40 50 T1 T2 T3 T4 SP CA CA CA CA AR CA AR DO QZ CA SP PL AR Figure 38 X ray d iffraction patterns from Ocean canal sediments T1 to T4. Table 311. Minerals identified in sediments of Miami, WPB and Ocean canal sediments from T1 to T4. Canal Transect Minerals SP QZ CA DO AR SM KL PL Ocean T1 T2 T3 T4 SPSepioliteMagnesium Silicate [Mg4Si6O15(OH)2 6H2O)] QZ Quartz Silicon dioxide (SiO2) CA Calcite Calcium carbonate (CaCO3) DO Dolomite Calcium magnesium carbonate,[CaMg(CO3)2] AR AragonitePolymorph of calcium carbonate, (CaCO3) SM Smectite (determined by removing carbonate and organic matter) KL Kaolinite (determined by removing carbonate and organic matter) PL Palygorskite Magnesium Alumini um Phyllosilicate (Mg,Al)2Si4O10(OH)4(H2O) (determined by removing carbonate and organic matter).

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101 CHAPTER 4 PHOSPHORUS RELEASE F ROM THE MAIN CANAL S EDIMENTS OF THE EVERGLADES AGRICULTU RAL AREA (EAA) 4.1 Introduction Phosphorus (P) in water bodies can hav e both external and internal sources. External sources of P can be agriculture or point sources like industrial or domestic effluents. Sediments can also release P, acting as an internal source of P to the overlying waters at levels comparable to external sources (Welch and Cooke, 1995; St einman and Reddy, 2004). Internal loading is the recycling of nutrients from bottom sediments to the overlying water column (Bostrom et al., 1982 ; Carpenter, 1983; Marsden, 1989). After the external load reduction, the internal loads of sediments determine the trophic status of a water body and the time for recovery (Petterson, 1998). The release of P is controlled by a number of physical, chemical and biological processes (Bostrom et al., 1982). The various physicochemi cal factors affecting P sorption and release from sediments are redox potential (Eh), pH, temperature, and bioturbation/mixing (Andersen, 1975; Holden and Armstrong, 1980; Bostrom et al., 1982; Sondergaard, 1989). Various compounds can bind phosphorus effi ciently like iron (III) and aluminum (III) hydroxides, clays, calcium, and humic substances (Bostrom et al., 1982). Phosphorus release from sediments can occur through hydrolysis of Fe/Al bound P; dissolution of Ca bound P, and mineralization of organic P (Pant and Reddy, 2001). 4.1.1 Influence of Redox on P Release Inorganic P can be held as Fe and Al phosphates in wetland systems (Khalid et al., 1977). According to Mortimer (1941, 1942), P flux at the sediment water interface is

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102 primarily controlled by the ferric (Fe, III) iron, to which phosphate adsorbs forming FeOOH PO44.1.2 Influence of Sediment pH on P release complexes. Below a redox potential of 80 mV at pH 7 insoluble iron (III) is reduced to iron (II) and dissolved P is fluxed into the water column ( Reddy and DeLaune, 2008). The reduction of iron (III) can be induced by organic acids and sulfides (Bostrom et al., 1982). While P associated with the amorphous Fe and Al oxides readily desorb the crystalline forms are desorbed only under extended water logged conditions (Reddy et al., 1995). Moore et al. (1998) indicated that the P flux from the sediments of l ake Okeechobee was sensitive to changes in redox reactions and oxygen status of the overlying water. However it was found that redox had greater influence on noncalcareous than calcareous sediments (Holdren and Armstrong, 1980). Inorganic P can be retained as insoluble CaP or Mg P compounds in alkaline wetland s ediments (Moore and Reddy, 1994; Reddy et al., 1999; Richardson, 1999). Acid fermentat ion products released due to microbial degradation of organic matter can lower the interstitial pH that can cause dissolution of carbonate minerals mobilizing calcium, and magnesium associated P (Marsden, 1989). In addition, competition between hydroxyl and phosphate ions at high pH conditions can cause P release from clays, oxides and hydroxides of Fe and Al (Lijklema, 1980; Stauffer and Armstrong, 1986). 4.1.3 Phosphorus Flux from Sediments Phosphorus flux to the overlying water column can be controlled by mineral solubility (Haggard, 2005) within the sediments. Using equilibrium calculations (Moore et al. 1991, 1998) showed that P solubility can be controlled by Ca mineral and Fe mineral precipitation. Oxygenated water has a redox potential of around +500 mV that

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103 decreases rapidly and at sediment depth of 1cm the redox potential and oxygen concentration can be about 200 mV and 0.1 mg L14.1.4 Influence of Organic Matter on P release respectively (Bostrom et al., 1982). Anoxic conditions can lead to a decrease i n pH which can dissolve apatite (Stumm and Morgan, 1970; Golterman, 1998, 2001). Iron and P may not exist as apatites but may exist as different as ferrosoferric hydroxyphosphates and strengite under oxidized conditions and vivianite under reducing conditions (Nriagu and Dell, 1974; Patri ck et al., 1973). The lack of crystalline forms of CaP minerals can be due to several factors including inhibition in mineral formation due to presence of carbonates (Stumm and Leckie, 1970), organic acids (Inskeep and Silvertooth, 1988) and absence of seed crystals (Griffin and Jurinak, 1973). P release fro m organic matter under oxic conditions has been reported by Boers and Van Hese (1988), Boers and De Bles (1991), and Sinke et al. (1990). M ineralization of organic material can occur rapidly under aerobic conditions thus potentially releasing P into the water column (Marsden, 1989). B ut organic matter mineralization can generate P flux in anaerobic conditions as well (Golterman, 2001) Under anoxic conditions bacterial populations turn to anaerobic fermentation and in order to acquire the same energy as aerobic respiration they decompose a large part of organic matter thus releasing P (Golterman, 2001). Apart from releasing P through mineralization, organic ma tter functions as electron donor thereby affecting redox and subsequently (Golterman, 1975) influencing P flux from sediments. Organic acids can also act as chelating agents by sorbing calcium, iron, manganese and aluminum (Bostrom et al., 1982; Lijklema, 1985). This competitive exclusion can reduce P adsorption thus giving rise to P flux to the water column

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104 (Stauffer and Armstrong, 1986). Complexation of organic acids with iron particles can ultimately hinder the precipitation of iron phosphates, and in th e process leaves dissolved P in the water column (Pizarro et al., 1995). Organic P can occur in a wide variety of compounds including phospholipids, nucleic acids, inositol phosphates, phosphoproteins, sugar phosphates and phosphonic acids (McKelvie, 2005) Different organi c P compounds including diester P, polynucleotides, nucleosides, monophosphosphates, glycerophosphoethanolamine, phosphoenolpyruvates and pyrophosphates have been identified by researchers in the Everglades incl uding STA 1W (Pant et al., 2002; Turner et al., 2006), WCA 1 and WCA 2 (Turner and Newman, 2005). I nvestigations by Ahlgren et al. (2006) and Hupfer and Lewandowski (2005) in twenty two lakes in Europe with different trophic conditions showed that organic P compounds especially poly phosphates can al so undergo internal loading and can contribute significantly to P release Due to the deposition of detr ital matter in canal sediments and the presence of readily degradable phosphate diesters (Turner et al., 2006) organic P compounds can play an important role in internal P loading to the water column in EAA canals. 4.1.5 Other Factors I nfluencing P Release Adsorption of phosphates can occur on clay minerals like kaolinite involving chemical binding to positively charged Al3+ edges of clay plates ( Stumm and Morgan, 1970). The formation of ferrous sulfides can also reduce P sorption (Marsden, 1989) and liberate P to the water column. Water movement and turbulence within the sediment water column can significantly increase the P flux and maintain a high P concentration gradient thus increasing P diffusion from the sediments (Marsden, 1989).

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105 The Everglades Agricultural Area (EAA) in S outh Florida is between situated l ake Okeechobee and the Water Conservation Areas (WCAs) comprises 2,872 km2 of (SFER 2010) of cultivated Histosols. Agriculture in EAA is focused on sugarcane but other crops like corn, winter vegetables and sod are also grown (Bottcher and Izuno, 1994) The EAA is distinguished by flat topography, shallow soils and seasonally h igh water tables underlain by limestone bedrock. Owing to flat topography in EAA drainage is accomplished through a network of pumps and canals. Drainage from farms are pumped into farm canals that are managed by farm owners. The farm canals drain into th e main canals. Main canals originate from the l ake Okeechobee and are operated by the SFWMD. During the dry season irrigation water is pumped into the fields while in the wet season excess precipitation is pumped off the farms into the canals. Drainage wat er is routed from the farm canals to the main canals and into the Stormwater Treatment Areas (STAs). The STAs are constructed wetlands for P removal through biological removal and subsequent sequestration by sedimentation. Phosphorus fertilization, soil or ganic matter oxidati on (subsidence) and inflow water from l ake Okeechobee are the main sources of P exported to the EAA main canals (Sanchez and Porter, 1994; Stuck, 1996). It is estimated that nearly 2.5 1012 m3 (SFER, 2010) of water, and nearly 129 met ric tons P per year (SFER, 2010) is discharged annually from the EAA into the Everglades Protection Area. Water pumped out of the EAA contains P in the dissolved (orthophosphate and soluble organics) and in the particulate form (minerals and particulate organics) (Daroub et al., 2002 a ). Phosphorus transported to the main canals accumulate in the sediments and the capacity of sediments to retain or release P can af fect water quality. E verglades A gricultural A rea canal sediments can act as potential P

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106 source and generate an internal load of P to the overlying water column which is delivered to the rest of Everglades. In addition the main canal sediments are subject t o transport and these sediments can act as a P source when transported to the downstream ecosystems Sediment core incubation studies have been performed in the Everglades and elsewhere to determine P flux in the sediments in wetlands in l ake Okeechobee ba sin the WCAs, l ake Apopka and the Lower St Johns River (Dunne et.al., 2006; Fisher and Reddy 2001; Moore et al., 1991; Malecki et.al., 2004). Sediment incubation studies were also performed in the canals of the STAs by Clark and Reddy ( 2002) but have not been used to date to determine the P flux from the main canals in the EAA. Thus P release capabilities of the EAA main canals are not known and our goal was to use intact sediment columns to determine P release and understand the P release characteristics associated with internal loading. We hypothesized that, sediments with high organic matter content and high NaOH extractable P will have higher P release compared to sediments with low organic matter and low NaOH extractable P; also sediments with high HC l extractable P will have low P release. Our objectives were to: (i) study P release characteristics of three main canals in EAA: Miami canal, West Palm Beach canal and Ocean canal sediments based on incubation experiments, and (ii) evaluate f actors such a s bulk density (BD), pH, P fractions, amorphous Fe and Al oxides, and Ca and Mg carbonates that may affect sediment P release within the canals.

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107 4.2 Materials and Methods 4.2.1 Study Site Description Sediments for the study were collected from Miami canal situated in western EAA, West Palm Beach canal (WPB) situated in eastern EAA, and Ocean canal situated in southeast EAA. Water used in the incubation study was collected from Arthur R. Marshall Loxahatchee National Wildlife Refuge. Pumping in these canals is managed by the South Florida Water Management District (SFWMD) and thus these canals are also called district canals. 4.2.2 Sediment Sampling Intact sediment cores were collected from four different transects from Miami, WPB and Ocean canal. T hus we have four different transects (T1, T2, T3 and T4) in each of the canals (Figure 4 1). The first transect (T1) for Miami and West Palm Beach canal was closest to the lake while the other transects (T2, T3 and T4) were taken progressively southward into EAA. T he average distance between the transects in Miami and WPB canals were 10.7 km (Table 38). The first transect (T1) in Ocean canal was closest to the WPB canal and the fourth transect (T4) was closest to the Hillsboro canal. The average distance between th e transects in Ocean canal was 2 km. Three cores from each of the four transects and from each of the three main canals were collected leading to a total of 3(cores) x 4(transects) x 3(canals) = 36 cores. Thus 36 intact sediment cores along with 2 blank cores (no sediment) were used for the incubation experiment. Details about sediment sampling and descr iption of Miami, WPB and Ocean c anals have been provided in Chapter 3.

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108 4.2.3 Sediment Core Incubation Canal water from the sediment cores was carefully siphoned off and th e cores were refilled with 275 mL water collected from Arthur Raymond Marshall Loxahatchee wild life refuge. Before each of the three exchanges, water was collected from the Arthur Raymond Marshall Loxahatchee wild life refuge and stocked. T he SRP concentration of water collected from the refuge during the first, second and third exchanges were 0.008, 0.004 and 0.007 mg L1 respectively A 20 cm water column was maintained above the sediment layer in the cores (Malecki et al., 2004) The wate r columns in the cores were maintained under aerobic conditions by bubbling air using aquarium pumps via tubing inserted into the water columns. The floodwater dissolved O2 concentrations were maintained between 5 and 8 mg L1Three floodwater exchanges were performed at the interval of 28 days. During exchanges water from the sediment cores were suctioned using a syringe fitted with tubing and with minimum disturbance to the sediment column. The cores w ere then refilled with stock 275 mL, 0.008, 0.004 and 0.007 mg L Bubbling air through the wat er column ensured aerobic conditions in the water columns (Gale et al., 1994). The interior of the incubation box was lined with black polythene to exclude light and prevent algal growth. The sediment cores were incubated in water bath to maintain a consta nt temperature (212C). 14.2.3.1 Collection of water s amples water during the first, second and third exchange respectively and incubated for another 28 days. Prior to sampling, the aerator was turned off to minim ize disturbance. Water column pH (Fisher scientific, accumet AP 85) and dissolved oxygen ( Fisher scientific oxygen meter 06662 66) of the water column from each core was measured before

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109 sampling. A 20 mL sample was pipetted from the water column, filtered through a 0.45 acid colorimetric method (EPA 1993, Method 365.1). Each time during sampling, water taken out was replenished with equal volume (20 mL) of stock P solution. The loss of water due to evaporation was replenished everyday by double distilled water. 4.2.3. 2 Estimation of P flux The estimation of P released/retained was calculated by the product of the volume of the water column multiplied by the difference in co ncentrations of the water column as shown below ( St einman and Reddy, 2004): Ct = SRP concentration (mg L1C ) of the overlying water at time t days t 1 = SRP concentration (mg L1V ) of the overlying water at time t 1 days TA = The inner cross sectional area of the sediment cores (m = The total volume (L) of the water column overlying the sediment 2Thus P released/retained = ) T t tV C C *1 Phosphorus flux from sediment to the water column was estimated by plotting cumulative SRP release/retention (Malecki et al., 2004) per unit surface area of the sedim ent column. Sediment P fluxes were calculated as linear changes in P mass in the overlying water after correction for sampling volume divided by the internal area of the sediment cores. Flux calculations were based on the increase/decrease of the amount of P in the water column. Ph osphorus flux is calculated as SRP released/retained per unit surface area as: Flux = A V C CT t t/ *1 equation (1)

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110 The amount of P removed during sampling was also accounted for as the product of the sampling volume and the difference between the concentration of the water taken and the concentration of the water added. Cs = concentration (mg L1V ) of the water replaced aft er sampling sC = volume of water (L) taken for s ampling. t = SRP concentration (mg L1Thus P removed (mg) due to sampling = ) of the overlying water at time t days s s tV C C equation (2) Hence the total change in P (mg) = the sum of P released/retained and P removed during sampling. i.e. equation (1) + equation (2) P = s s t T t tV C C V CC *1 equation (3) Total flux of P (mg m2 A V C C V C Cs s t T t t/ *1 ) (Reddy et al., 2007) = equation (4) To determine release and retention on a daily rate basis release and retention data were divided by number of sampling days per sampling period. Phosphorus mass release/retention at each sampling event was then converted to a rate (mg m2 d14.2.4 Sediment Analysis ) by dividing by time or the number of sampling days per sampling event ( Clark and Reddy, 2002). Sediment P release can occur due to a com bination of chemical factors including sediment physicochemical pr operties (Andersen, 1975; Holden and Armstr ong, 1980; Bostrom et al ., 1982; Sondergaard, 1989), different P fractions (Pant and Reddy, 2001; Moore and Reddy; 1994; Reddy et al., 1999; Richardson, 1999) and the presence of amorphous Fe and Al oxides and Ca and Mg carbonates ( Mortimer, 1941, 1942;

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111 Bostrom et al., 1982; Reddy et al., 1995). The dependence of P release from the EAA sediments on these factors is not well established. Our investigation considered the effects of these factors affecting P release from the EAA canal sediments 4.2.4.1 Sediment physicochemical prope rties Sediment samples were analyzed for %Loss on ignition ( % LOI), total P, BD, and pH. The details of the methods are provided in chapter 3. 4.2.4.2 Phosphorus fractionation Sequential extraction was performed according to the method of Chang and Jackson ( 1957 ) modified for wetland soils (Qualls and Richardson, 1995; Reddy et al., 1998; Reddy et al., 2007). The detailed procedure of P fractionation is provided in Appendix A. 4.2.4.3 Extractable Fe and Al Active amorphous Fe and Al oxide was extracted using 0.2 M ammonium oxalate and 0.2 M Oxalic acid at pH 3.0 (Loeppert and Inskeep, 1996; McKeague and Day, 1966) after pretreating the samples with ammonium acetate for calcium carbonate (CaCO34.2.4.4 Extractable Ca and Mg ) (Loeppert and Inskeep, 1996). Ext ractable Ca and Mg were determined by 0.5 N acetic acid extracting solution (Sanchez, 1990). The extracts were analyzed for Ca and Mg by Atomic Absorption Spectrometry (AAS). 4.2. 5 Statistical Analysis Calculation of P flux from intact cores was done by si mple linear regression of the concentration versus time curve for the initial period of P flux. The mean and standard deviation of each parameter used for %LOI, total P, BD, pH and P fractions and P

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112 fluxes were calculated with Excel (Microsoft, 2000). Det ermination of the relationship between P flux, soil physicochemical properties, P fractions and extractable Fe, Al, Ca and Mg were performed using SAS statistical program (proc CORR) (SAS Institute, 2003). 4.3 Results and Discussion 4.3.1 Phosphorus Releas e from Canal Sediments 4.3.1.1 Miami canal The P release values from Miami, WPB and Ocean canal sediments varied extensively between the transects, canals and floodwater exchanges. In exchange 1 (Figure 4 2), sediments from Miami canal T1 and T4 had lower cumulative P release rates (31.9 and 37.0 mg m2 respectively) than T2 and T3 (107 and 86.9 mg m2 respectively ) During exchange 2, the cumulative P release values of all transects decreased and the same P release trend as exchange 1 was observed i.e. T2 and T3 had higher cumulative P release rates (70.5 and 77.1 mg m2 respectively) than T1 and T4 (35.6 and 18.8 mg m2 respectively). During exchange 3, the cumulative P release rates of all four transects decreased from exchange 1 and e xchange 2. During exchange 3, T1, T2 and T3 had comparable cumulative P release values of 18.9, 16.7, 18.7 mg m2 respectively Transec t 4 at exchange 3 had the lower P release value among all the exchanges and transects in Miami canal. Total P released from Miami canal sediments over all the three exchanges were about 600 mg m2 for T2 and T3 (Figure 4 3). For T1 and T4 the total P released over all the three exchanges were about 300 and 200 mg m2 respectively. Similar to cumulative P rel ease values, P flux from Miami canal sediments T1 and T4 (1.1 and 1.3 mg m2 d1) were lower than T2 and T3 (Figure 4 4 ). Similar P flux values (1 mg P m2 d1) were calculated for lake

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113 Okeechobee sediments by Moore et al.,1998. The Miami canal is located in the S8 basin of the EAA. The S8 basin had a P load of 16300 kg yr1 in water year 2008 ( SFER, 2009.) Multiplying cumulative P release by Miami canal area gives P load that can rang e from 30.1 to 101.6 kg month1 or 361.7 to 1218.8 kg yr14.3.1.2 West Palm Beach canal Phosphorus release from Miami canal roughly estimated was about 27% of the total P load of the entire S8 basin. The P release values from WPB canal sediments were lower than that of Miami canal at all transects and exchanges (Figure 4 5) Within WPB canal T4 had least cumulative P release values at all the three exchanges, (6.9, 3.0 and 2.9 mg m2 for exchange 1, 2 and 3 respectively) During exchange 1, cumulative P release values of T1, T2 and T3 were 31.2, 28.1 and 26.5 mg m2. Similar to Miami canal, P release values decreased at all transects at WPB canal for exchange 2 and 3. Total P released from WPB canal sediments over all three exchanges were about 100 mg m2 for T1, T2 and T3 (Figure 46). For T4 total P released over the three exchanges was about 50 mg m2. The P flux values of WPB canal T1, T2 and T3 were greater than T4 during all exchanges (Figure 47). Both cumulative P release values and daily P release values of WPB canal sediments were lower than Miami canal sediments. The WPB canal is located in EAA S5A basin. The S5A basin had a total P load of 50000 kg yr1 in water year 2008 (S FER, 2009 .). Multiplying cumulative P release by WPB canal area gives P load that can range from 14.0 to 63.5 kg month1 or 168 to 762 kg yr1, corresponding to approximately less than 0.1% of the total P load for the entire S5A subbasin.

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114 4.3.1.3 Ocean canal Ocean canal P release values were comparable to P release values o f WPB canal sediments (Figure 48). Within the transects of Ocean canal, the highest cumulative P release was observed at T2 4 3.1, 25.1 and 9.3 mg m2 during exchange 1, 2 and 3 (Figure 4 8). Cumulative P release of T1, T3 and T4 were 24.2, 21.9 and 20.6 m g m2 during exchange 1. Similar to Miami canal and WPB canal sediments cumulative P release decreased at all transects during subsequent exchanges. Total P released from Ocean canal sediments over all three exchanges was about 65 mg m2 for T1, 200 mg m2 for T2, 150 mg m2 for T3 and 140 mg m2 for T4 (F igure 49). The P flux values decreased during subsequent exchanges at all transects in Ocean canal (Figure 410). Ocean canal is located in the S5A basin. Multiplying cumulative P release by Ocean canal area gives P load that ranges from 14.2 to 29.7 kg month1 or 170 to 356 kg yr1. West Palm Beach and Ocean canals have a total P load ranging from 339 to 1120 kg yr14.3.2 S ediment Physicochemical P roperties Combined P release from WPB and Ocean canal comprise about 0.07 to 2% of the total P lo ad of the S5A basin. Everglades Agricultural Area, main canal sediment physicochemical properties are provided in chapter 3, section 3. 3.1. 4.3.3 Sediment P Fractions Information in EAA main canal sediment P fract ions are provided in chapter 3, section 3. 3.2. 4.3.4 Extractable Fe, Al, Ca and Mg Extractable Fe concentration varied from 62.6 to 906 mg kg1 in Miami, WPB and ocean canal sediments while Al concentration varied from 23 to 195 mg kg1 (Table 41)

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115 The Fe and Al concentrations measured in the Histosols of EAA by Janardhanan and Daroub (2010) were much higher and averaged 7 355 g kg1 and 1 715 g kg1. It is possible that Fe(III) in canal sediments were reduced to soluble Fe(II) that was released in ca nal water thus leading to low Fe concentrations in the sediments. The Ca concentrations were higher than Fe and Al concentrations and varied from 1816 to 32400 mg kg1 in Miami, WPB and Ocean canal sediments. Magnesium concentrations were lower than the Ca concentrations and varied from 213 to 1285 mg kg14.3.5 Factors Affecting P R elease in Miami, WPB and Ocean canal sediments Sediment total P release from Miami, WPB and Ocean canals were significantly correlated with both amorphous Fe and Al concentrati ons but were not significantly correlated with Ca and Mg concentrations (Table 41) This signifies that even though present in lower concentrations than Ca and Mg, amorphous Fe and Al concentrations significantly affect P flux in EAA canals. Similarly Jan ardhanan and Daroub (2010) found that P sorption capacities of the EAA H istosols were affected by the amorphous Fe and Al concentrations than the CaCO3 concentrations. Hayes (1964), Lijklema (1977) found that sorption efficiencies for iron oxides and hydroxides are greatest around pH 6 and decrease with increase in pH. The EAA canal sediment pHs were circumnetral which may have lead to reduced sorption capacity leading to P release which explains the dependence of P release with extractable amorphous Fe. Though present in lower concentrations than Fe the dependence of P release with Al signifies the sensitivity of Al phosphate complexes to undergo release in EAA canal sediments. Though present in large quantities P release in calcareous EAA canal sediments were not significantly related the Ca and Mg concentrations Calcium in EAA canal sediments

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116 can exist as calcium carbonates/calcites (as verified by mineralogical analysis of the main canal sediments in chapter 3, section 3.3.3) or as dissolved Ca2+P hosphorus rel eased from EAA main canal sediments was n ot significantly correlated with sediment physicochemical properties including BD, %LOI and pH (Table 4 1). Low bulk density values can be a very important factor in the EAA canals causing increased P flux to the water column by sediment resuspension and by maintaining a concentration gradient owing to the action of pumps. High P release rates due wind induced turbulence and flushing in lakes were reported by Andersen (1974), Ryding and Forsb erg (1977), Ahlgren (1980) and Poon (1977). The sediment layers in the intact sediment columns in the laboratory did not undergo any disturbance to affect P release which may explain the non dependence of P release with BD values. Organic matter cannot bind phosphate by itself and is dependent on associated metals such as Fe and Al (Bostrom et al., 1982). Organic materials have strong tendency to chelate iron which is diminished in presence of high concentrations of Ca ions. P hosphorus associated with Ca can be released by the dissolution of carbonate minerals by acid fermentation products (Marsden, 1989) or by competing hydroxyl ions substituting phosphates at high pH values (Lijklema, 1980; Stauffer and Armstrong, 1986) Mo st probably there were not enough of the acid fermentation products produced to dissolve carbonates to release P as well as the pH values were not high enough to substitute phosphates with hydroxyls. 2+ ( Williams, 1970; Shukla et al., 1971) It is possible that high concentrations of Ca2+ ions in EAA sed iments was hindering the association of organic matter with phosphates thus leading to no relationship with P release in these sediments. The significant correlation of P release

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117 with sediment Fe concentration suggests that P release should be correlated w ith sediment pH values too. The sediment pH values recorded in the experiment were not the sediment core pH values during the course of experiment but were sediment pH values recorded at the beginning of the experiment which does not reflect the pH change that occurs during the course of the incubation period. Perhaps this is why we do not observe any correlation of P release with sediment pH. Sediment total P release from Miami, WPB and Ocean canals w as significantly correlated total P (Table 42 ) but not with individual P fractions The dependence of P release on total P is indicated by the very low P release from Ocean canal sediments that had the smaller sediment total P values and high P release from Miami canal sediments that had greater total P values (Table 32). The lack of significant correlation of individual P fractions with P release indicates that several factors are likely controlling P release in these canal sediments. Furthermore the lack of correlation of P fractions with P release could mean that P mobilization by the different fractions does not necessarily result in P release but in many cases can result in transfer from one fraction to another (Bostrom, 1982). For example subsequent hydrolysis of organic phosphates may not result in P rel ease but can be sorbed onto Fe(III) complexes or P released from Fe/Al or Ca/Mg can be taken up by microorganis ms (Bostrom, 1982). Apart from sediment properties, other factors may have influenced P release, like the presence of shells and the distribution of carbonate layers in canals Ocean canal sediments had a layer of sea shells on the sediment surface and sea shells distributed throughout the sediment column (Figure 4 12 ) The presence of shells on the sediment surface possibly decreased the effective surface area which also could have contributed

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118 to the low P release from Ocean canal sediments. The low P release from WPB canal sediments in spite of having comparable total P, BD, %LOI and pH v alues (Table 32 and 33) with Miami canal, could be due to alternating carbonate layers distributed throughout the sediment column inhibiting P release from sediments (Figure .4 13, 414, 4 15). Alternating climatic conditions favoring peat and calcite formation have been documented by Gleason and Spackman (1974) leading to inter bedding of peat and carbonate layers in parts of EAA 4.4 Conclusions Phosphorus releases from EAA main canal sediments have been found vary among the three main canals in this st udy Based on sediment physicochemical properties and P release characterist ic s Miami canal and Ocean are two very different canals. Miami canal sediments had high organic matter and high total P. Ocean canal sediments on the other hand were v ery mineral i n nature with low er organic matter and lower total P. P hosphorus release from Miami canal sediments was much higher than Ocean canal sediments which support the correlation of P release with total P. T he function of o rganic matter in P release is not clear as there was no correlation of P release with organic matter in the EAA canals. O rganic matter can play an important role in facilitating P release by either masking adsorption sites or by acting as organic ligands and promoting P release. Support for this suggestion also stems from the fact that the fourth transect in Miami canal that was very mineral in nature had P release similar to Ocean canal sediments. Similar low P release was observed in EAA agricultural ditches by Collins (2005) where he estimated greater P release in ditches with organic sediments compared to mineral sediments. West Palm Beach canal which is similar to Miami canal in physicochemical properties and total P content had P

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119 releases comparable to Ocean canal s ediments. We suspect that though WPB canal sediments have the potential to release P, the a lternati ng distributions of carbonate layers may have reduced P release to water column. Thus not only sediment properties but also the distributions of the sediment layers influence P release in EAA. The presence of a surface shell layer was also thought to inhibit P release by reducing the effective surface area in Ocean canal. Therefore P release in organic matter rich sediments in EAA which are expected to have hi gh P release can behave in the opposite way if sediment bed is not completely in contact with the water column due to presence of shells. Phosphorus release from Miami canal ranged from 27% of the total P load from Miami canal basin (S8), while WPB Ocean canal combined contributed approximately 0.072% of the total P load in the WPB Ocean (S5A) subbasin respectively. Based on the incubation experiments we conclude that the EAA canals do release P. The incubation experiments showed that, the canal sediment s can act as a P source for at least a period of 84 days. This P release was conducted in the laboratory under controlled conditions and only diffusive fluxes from the sediments were considered. In canals, factors like canal flow conditions, resuspension a nd continuous addition of P can increase the magnitude as well as prolong the time of the P release. Future studies should focus on the evaluation of the extent and dependence of this P release on external P concentrations. Future research should also investigate the chemical characteristics of organic matter facilitated P release and mineral P release in EAA canals from different basins and topographical regions.

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120 Figure 41 Transect locations T1 to T4 of Miami canal WPB canal and Ocean canal in Everglades Agricultural Area.

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121 0 20 40 60 80 100 120 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 P mass release (mg m 2 ) Time (days) T1 T2 T3 T4 1stfloodwater exchange (028 days) 2ndfloodwater exchange (2956 days) 3rdfloodwater exchange (5784 days) Figure 42 Phosphorus release from Miami canal sediments T1T4 and exchange 1, 2 and 3. .

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122 100 50 200 350 500 650 0 1 2 4 7 14 21 28 29 29 30 32 35 42 49 56 57 57 58 60 63 70 77 84 P released (mg m 2 ) Time (days) T1 T2 T3 T4 2ndexhange (28-56 days) 3rdexhange (56-84 days) 1stexhange (0 -28 days) Figure 43 Total P released from Miami canal sediments over exchange 1, 2 and 3. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 T1 T2 T3 T4 P flux (mg m 2 d 1 ) Exchange 1 Exchange 2 Exchange 3 Figure 44 Phosphorus flux from Miami canal sediments T1T4 and exchange 1, 2 and 3.

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123 0 5 10 15 20 25 30 35 40 45 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 P mass release (mg m 2 ) Time (days) T1 T2 T3 T4 1stfloodwater exchange (028 days) 2ndfloodwater exchange (2956 days) 3rdfloodwater exchange (5784 days) Figure 45 Phosphorus release from WPB canal se diments T1T4 and exchange 1, 2 and 3.

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124 25 25 75 125 175 225 0 1 2 4 7 14 21 28 28 29 30 32 35 42 49 56 56 57 58 60 63 70 77 84 P released (mg m 2 ) Time (days) T1 T2 T3 T4 1stexchange (0 -28 days) 2ndexchange (28-56 days) 3rdexchange (56-84 days) Figure 46 Total P released from WPB canal sediments over exchange 1, 2 and 3. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 T1 T2 T3 T4 P flux (mg m 2 d 1 ) Exchange 1 Exchange 2 Exchange 3 Figure 47 Phosphorus flux from WPB canal sediments T1T4 an d exchange 1, 2 and 3.

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125 0 5 10 15 20 25 30 35 40 45 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 P mass release (mg m 2 ) Time (days) T1 T2 T3 T4 1stfloodwater exchange (028 days) 2ndfloodwater exchange (2856 days) 3rdfloodwater exchange (5784 days) Figure 48 Phosphorus release from Ocean canal sediments T1T4 and exchange 1, 2 and 3.

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126 25 25 75 125 175 225 0 1 2 4 7 14 21 28 29 29 30 32 35 42 49 56 57 57 58 60 63 70 77 84 P released (mg m 2 ) Time (days) T1 T2 T3 T4 2ndexchange (28-56 days) 3rdexchange (56-84 days) 1stexchange (0 -28 days) Figure 49 Total P released from Ocean canal sediments over exchange 1, 2 and 3. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 T1 T2 T3 T4 P flux (mg m 2 d 1 ) Exchange 1 Exchange 2 Exchange 3 Figure 410. Phosphorus flux from Ocean canal sediments T1T4 and exchange 1, 2 and 3.

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127 Table 41 Ammonium oxalate extractable Fe, Al, and acetic acid extractable Ca, Mg from Miami, WPB and Ocean canal sediments Canal Transect Feox mg kg1 Alox mg kg1 Ca mg kg1 Mg mg kg1 Miami T1 677 195 26000 1280 T2 661 170 17600 678 T3 906 124 8240 615 T4 606 123 24900 461 WPB T1 62.6 23 0 1820 213 T2 489 98 0 18500 754 T3 971 122 7150 1240 T4 846 123 6530 796 Ocean T1 385 99.4 22000 644 T2 169 59.9 31600 582 T3 330 122 20800 685 T4 248 59.3 32400 468 Table 42. Correlation of total P released from canal sediments over exchange 1, 2 and 3 with sediment physicochemical properties BD, %LOI, pH, Fe, Al, Ca and Mg Table 43 Correlation of total P released from canal se diments over exchange 1, 2 and 3 with total P and sediment P fractions Significant at the 0.05 probability level ** Significant at the 0.01 probability level ns Not significant Fe Al Ca Mg BD %LOI pH Total P released 0.64* 0.64* 0.42 ns 0.47 ns 0.28 ns 0.29 ns 0.30 ns Total P KCl NaOH Pi NaOH Po HCl Res Total P released 0.41** 0.33 ns 0.004 ns 0.25 ns 0.25 ns 0.04 ns

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128 y = 0.8544x 0.0056 R = 0.96 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Total P (mg L 1 ) SRP (mg L 1 ) Figure 411. Correlation between water column total P and SRP from sediment incubation study Figure 412. Sediment surface layer of sediment core from Ocean canal Figure 413. Sediment surface layer of sediment core from WPB canal

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129 Figure 414. Sediments from WPB canal Figure 415. Sediment cores from WPB canal showing layer s of CaCO3

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130 CHAPTER 5 DETERMINATION OF EQU ILIBRIUM PHOSPHORUS CONCENTRATIONS OF EA A MAIN CANALS 5.1 Introduction Phosphorus (P) is the limiti ng nutrient for algal growth in freshwater ecosystems and P loading from the Everglades Agricultural Area ( EAA) is considered to be the major cause of eutrophication in the Everglades (Pant et al., 2002) Phosphorus is usually considered to be the limiting nutrient in freshwater ecosystems, including streams and lakes whereas N is considered the limiting nutrient in marine ecosystems primarily due to enhanced iron sequestration by sulfides The EAA lies in South Florida between l ake Okeechobee to the north and the Water Conservation Areas (WCAs) and the Everglades National Park (ENP) to the south. The EAA is drained by a network of canals consisting of farm canals and main canals. The farm canals are managed by EAA farm owners and are used to drain and irrigate the farms. The drainage from the farm canals are pumped into the main canals which are managed by the South Florida Water Management District (SFWMD). The entire water system is hydrologically connected thus P sourced from the lake and the EAA farms can end up in the P limited ecosystem of the Everglades through the EAA canals. The EAA canal sediments can act as a sink or alternatively due to years of agriculture and subsequent accumulation of P within the canal sediments, can act as a P source to the overlying water column. Thus these EAA canals can determine the water quality entering the P sensitive ecosystems of the south. Within EAA canals, sediment physicochemical and biological processes can play a central part in affecting resultant P concentration in canal water, and subsequent loads to downstream water bodies. The EAA canal sediments are compo sed of calcareous parent material as well as deposited particulate materi al from

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131 EAA farms. Equilibrium p hosphorus c oncentration (EPC) measurements of EAA canal sediments can be useful to identify the sediments as sinks or sources of P. The EPC is defined as the aqueous P concentration in the water column at which no net flux i.e. release or retention occurs from the sediments to the water column; and the P in solution is in equilibrium with P in the solid phase (Reddy et al., 1999). When soluble reactive P (SRP) in overlying water is greater than the EPC of the sediment, the sediment will remove SRP from the water column, and the opposite is true when SRP
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132 southern Everglades soil determined by Zhou and Li (2001) ranged from 0.002 to 0.010 mg L1Equilibrium phosphorus c oncentration values can be determined from adsorption isotherms (EPC 0) and incubation of intact sediment cores (EPCw). The EPC0, is calculated from batch adsorption experiments with varying P spike conc entrations. The EPCw5.1.2 Linear Adsorption Isotherms is the floodwater P concentration in intact sediment columns when there is no net P release/retention from the sediments. Equilibrium Phosphorus Concentration values are a measure of the potential of P loading from soils/sediments to t he water column. Phosphorus sorption isotherms can be used to determine the sediment EPC0 values from soils and sediments (Ruttenberg, 1992; Novak et al., 2004). The standard method for determining EPC0While it is common practice to determine sediment EPC by adsorption isotherms involves treating soil or sediment with varying P concentrations in KCl solution that are shaken overnight, centrifuged, filtered and analyzed for SRP (Pant and Reddy, 2001; Novak et al., 2004). The exchangeable P signifies the labile P that can desor b if the sediment acts as a P source. The difference in amounts of P added and recovered in solution at each concentration after equilibration are considered as P adsorbed /released by soil or sedi ment (Reddy et al., 1999; Pant and Reddy, 2001). 0 by linear adsorption isotherms, the experimental conditions do not represent the system and the parameters calculated from these adsorption isotherms can vary depending on contact/shaking time and temperature ( McGechan and Lewis, 2002). Laboratory batch incubation isotherms involve 24 h of shaking, but in reality phosphate sorption equilibrium can take weeks or years to come into effect (Hansen et al., 1999). During the adsorption isotherm

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133 experiments each parti cle is in contact with the extracting solution whereas in canals the sediment surface is in contact with the water column. The Langmuir equation was used to determine different adsorption parameters. The Langmuir equation was originally derived for describing the adsorption of gases onto solids and is based on assumptions of (i) a constant adsorption energy on a homogenous surface; (ii) no interaction between adsorbed molecules and (iii) the maximum adsorption being equal to a monomolecular layer of the ads orbed molecules (Bohn et al., 1985). These assumptions rarely occur in nature. Due to the various criticisms and limitations of using the linear adsorption isotherm we also determined EPC by incubation of intact sediment cores. 5.1.3 Incubation of Intact S ediment Cores Equilibrium phosphorus concentration (EPCw) values can also be calculated though intact sediment column experiments where P release/retention in soil/sediment columns are monitored with varying floodwater P concentration (Reddy et al., 1996; Nyugen and Sukias, 2002). The EPCw values are determined by plotting sediment P retained/released against the floodwater P concentration as the P concentration at which there is no P flux (Reddy et al., 1999). The exchange of sediment P to the water colum n can occur by i) sedimentation of inorganic and organic particulate P ii) uptake of SRP by primary producers and its subsequent settling iii) sorption of soluble inorganic and organic P onto particles that settle out onto the sediments or the sorption of soluble inorganic and organic particles onto sediments (Reddy et al. 1999). Phosphorus is released from the sediments when the porewater P concentration exceeds the water column P concentration (Moore et al. 1991). Phosphorus flux from sediment cores can be regulated by i) processes within the water column (mineralization, sorption by

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134 particulate matter, uptake and release by primary producers, ii) processes within the sediment column (mineralization, sorption, precipitation, dissolution and redox fluctua tion) and other factors like pH, temperature, organic matter content, and presence of metals (Holdren and Armstrong 1980; Moore et al., 1991). The possibility of the occurrence of all these processes within the incubated sediment cores may make the incuba tion experiment a better representation of the natural system, thus could be an improved way to determine EPC from P flux measurements. We hypothesize that the EPC values would vary according to the P release potential of the canal sediments and the adsor ption isotherm and incubation of intact sediment cores would yield similar EPC values. Our objectives were (i) to determine the EPC of three main drainage canals of EAA: Miami, West Palm Beach (WPB) and Ocean canal. (ii) to compare the EPC values measured by two methods: adsorption isotherms (EPC0) and (EPCw5.2 Materials and Methods ). A batch incubation experiment as well as in intact sediment core incubation study was conducted using the sediments collected from Miami, West Palm Beach (WPB) and Ocean can al Procedures for determining sediment physicochemical properties, P fractions and amorphous Fe, Al, Ca and Mg are documented in chapter 3 and chapter 4. 5.2.1 Study Site Description Sediments were collected from Miami canal situated in western EAA, West Palm Beach canal (WPB) situated in eastern EAA and Ocean canal situated in southeast EAA. Agricultural drainage water in EAA is pumped out of the farms to the farm canals

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135 and to the main canals which then flows downstream. The description of the study sites for Miami, WPB and Ocean canal s are discussed in chapter 3. 5.2.2 Collection of Sediment Cores Intact sediment cores were collected from four different transects (T1, T2, T3 and T4) from Miami, WPB and Ocean canals (Figure. 41). Three cores from each of the 4 transects and from each of the 3 main canals leading to a total of 3(cores) x 4(transects) x 3(canals) = 36 cores along with 2 blank cores (no sediment) were taken for the incubation experiment. Description of the sediment core collection procedure is provided chapter 4. 5.2.3 Phosphorus Adsorption Isotherm About 3 g of field moist sediments were mixed with 30 ml of P containing 0, 50, 100, 150, 200, 250, 500, and 1000 g L1 of KH2PO4 solution (Reddy et al, 1998; Pant and Reddy, 2001) with soil to solution ratio of 1:10. The KH2PO4 was made in 0.01M KCl medium as an ionic medium like KCl helps to reduce the pH dependant sorption (Giesler et al., 2005). To determine the potential maximum P sorption capacity of the canal sediments additional P isotherms of 5000, 15,000, 20,000 and 30,000 g L1 were conducted, and the data combined with the initial results. Sediment samples were shaken for 24 h on an orbital shaker and immediately centrifuged at 4000 rpm for 15 min. (Reddy et al., 1998; Giesler et al., 2005). The filtrates were analyzed for soluble reactive P (SRP) by ascorbic acid method (Murphy and Riley, 1962) using Lachat Quickchem FIA 8000 series. Quality assurance/quality control was strictly followed with calibration,

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136 standards, spikes, and blanks routinely included in the analysis. A check standard, duplicate and spike was included every after 10 samples. Estimation of EPC0 0S KC S by adsor ption isotherms Linear adsorption isotherms were used to determine sediment EPC values (Pant et al., 2002) which is given by The EPC values were calculated from regression statistics as the intersecting point on the x axis between S (y axis) against C (x axis) i.e. the concentration (C) when 0 S (Pant et al., 2002; Smith et al., 2005) S = quantity of P sorbed in the solid phase, g kg K = Phosphorus sorption coefficient 1 C = Solution P concentration following 24 h of shaking g L S1 0 Linear Langmuir isotherms were used to calculate P sorption maximum (S = Quantity of P originally sorbed by sediments (is the intercept on the y axis). max max / max / 1 / S C S k S C ) and other bonding energy (k), whi ch is given by (Reddy et al., 1998; Rhue and Harris, 1999; Pant and Reddy, 2001; Essington, 2004). C = Solution P concentration measured after 24 h equilibration (mg L 1S = Amount of P sorbed in solid phase (mg L ) 1S ) max = P sorpti on maximum (mg kg 1k = Sorption constant related to P bonding energy (L mg ) 1The linear Langmuir isotherm was constructed by plotting C/S vs S ) max max/ 1 S The slope is equal to and the intercept is equal to ) /( 1maxS k The sorption constant k, is equal to the reciprocal of equilibrium P concentration at one half saturation and is related to the bonding energy of the soil for phosphorus. An increase in the value of k indicates an increase in the bonding energy of the soil for P. (Olsen and Watanabe,

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137 1957). The Langmuir equation adsorption parameter Smax5.2.4 Sediment Core Incubation gives us an estimate of sediment P storage capacity. Five different floodwater exchanges consisting of 7 days each were performed with P spikes of 0.007, 0.05, 0.13, 0.27 and 0.35 mg L1 respectively. Spike for the 1st exchange was collected from A.R.M. Loxahatchee wildlife refuge which was of the required concentration thus not needing to add any further P. Other spikes were prepared a day before the exchange by adding appropriate P standard solution (KH2PO4Estimation of EPC ) to water collected from the refuge. The description of the of the incubation experiment, sampling and other details are provided in chapter 4. w from sediment incubation study Sediment EPCw values were determined by plotting P release as y axis against floodwater P spike concentration as x axis. Sediment P release was calculated as linear changes in P mass in the overlying water after correction for sampling volume divided by the internal area of the sediment cores (Malecki et al., 2004). Phosphorus flux was calculated as the product of volume of water column multiplied and P concentrations of the water column explained in chapter 4 ( St einman and Reddy, 2004). The EPCw values were determined as the intersection of daily P flux (y axis) with water column P concentration (x axis) which was accomplished by equating the straight line equation to zero and solving the value of x, i.e. the P concentration (Reddy et al., 1999; Leeds, 2006).

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138 5.3 Results and D iscussion 5.3.1 Miami Canal 5.3.1.1 Batch adsorption isotherm Sediment EPC values from batch adsorption isotherm studies were determined by plotting solution equilibrium P concentration on the x axis and P released/retained on the Y axis (Figure 51). Batch incubation studies of Miami canal yielded EPC0 values of 0.03, 0.03, 0.06 and 0.05 mg L1 of T1 T4 respectively (Table 51). Similar EPC0 values were found by Reddy et al., 2007 from l ake Okeechobee se diments where at depths 0, 30, 45, and 55 cm the EPC0 values were on the order of 0.03, 0.01, 0.02 and 0.04 mg P L1. Higher EPC0 (0.38, 0.30, and 0.34 mg P L1) values were found on the wetland soils of Orange County Florida experimental wetland site by G ale et al. (1994). The Smax values of Miami canal T1 to T4 were 666.7, 714.3, 909.1 and 1111 mg kg1. Thus T3 and T4 sediments have higher adsorption capacity than T1 and T2 sediments. The intensity of adsorption (k) of Miami canal transects T1 to T4 were 250, 357.1, 178.6 and 178.6 L kg15.3.1.2 Incubation of intact sediment cores Phosphorus release from T1T4 exchange 1 to 5 on Miami canal sediments (Figure 5 2) shows that the sediments released P during exchange 1 and 2 and retained P in exchange 4 and 5. Thus the EPCw values of the sediments should be between spike P concentration of exchange 2 (0.05 mg L1) and exchange 4 (0.27 mg L1). Sediment EPCw values were obtained by plotting P release with floodwater spike concentration (Figure 53) were 0.124, 0.159, 0.125 and 0.075 mg L1 from T1 T4 respectively (Table 52).

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139 There are notable differences between the EPC values generated by the adsorption isotherm and the incubation study method. First, the EPC values from the incubation study were higher tha n that obtained from adsorption isotherm studies by almost an order of magnitude which indicates that P release in sediment cores is higher than that in adsorption isotherms. This could be because EPC values from batch adsorption isotherms are calculated i n laboratory conditions where sediments are not influenced by canal conditions like the presence of plants and algae that can affect P release (Gale et al., 1994). Furthermore, overnight shaking ensures aerobic conditions in the tubes which can lead to low er P release and thus low EPC values. This is in contrast to incubation experiments where reducing conditions develop in sediments that can influence P release from reduction of iron (Fe III). Oxygenated water has a redox potential of around +500 mV which decreases rapidly with depth and at sediment depth of 1 cm the redox potential and oxygen concentration can be about 200 mV and 0.1 mg L1 (Bostrom et al., 1982). Pant and Reddy (2001) conducted studies on the sorption characteristics of the estuarine sedi ments of the Indian River Lagoon System under different redox conditions. Under anaerobic and aerobic conditions the mean EPC values of 0.75 mg L1 and 0.05 mg L1The reducing conditions arising in subsurface sediment layers can cause P release in incubation experiments as well as in canals resulting in higher P release and consequently higher EPC values. Sediment columns in porewater diffusion can also play a significant role in P release from canal sediments. Though EPC values from which made them conclude that higher EPC in the anaerobic conditions was due to P release f rom amorphous and poorly crystalline forms of iron (Fe III).

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140 adsorption isotherms were lower than that obtained from intact sediment study, according to batch adsorption study T4 had th e highest EPC value while according to incubation study method it was quite the opposite. Physicochemical properties of the canal sediments (Chapter 3, Table 31) indicate that T4 had highest total P but the P fractions showed that this huge amount of total P was mostly bound as HCl P (Chapter 3, Figure 33). It is possible that overnight shaking exposed all soil sorption sites bringing into solution P from otherwise unavailable pools. In contrast, in incubation experiments P diffuses from sediments to the water column without any external aid. 5.3.1.3 Phosphorus release and EPC The EPCw w values were significantly correlated with sediment P release (0.082***). Phosphorus released from Miami canal T1, T2 and T3 (78.6, 121, 105 mg m2) were higher than T4 (31.8 mg m2) (Figure 5 4).High P release values lead to high EPCw values which can be a result of high P loading in these sediments High P loading and the resultant high P release from the soils from a dairy operation farm in Okeechobee, Florida yielded an EPCw of 1.3 mg L1 (Pant and Reddy, 2003). The P retained by Miami canal sediments were 112, 99.0, 164 and 104 mg m25.4.1 WPB Canal for T1, T2, T3 and T4 respectively. 5.4.1.1 Batch adsorption isotherm The EPC0 values of WPB canal transects were 0.02, 0.04, 0.04 and 0.36 respectively (Figure 55 and Table 53). The EPC value of T4 was almost an order of magnitude greater than rest of the transects. The k values of WPB canal sediments were 555.6, 500, 277.8 and 15.4 L kg1 from T1 T4 respectively. T he high EPC value at

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141 T4 is reflected in the very low k value. West Palm Beach canal T3 had the least Smax (769 mg kg1) and T1 had the highest Smax value (1430 mg kg15.4.1.2 Incubation of intact sediment cores ). Phosphorus release from T1T4 exchange 1 to 5 from WPB canal sediments (Figure 5 6) show that during exchange 1 all the transects are releasing P. During exchange 2, at P spike concentration of 0.05 mg L1, T1 and T4 began retaining P while T2 and T3 sediments were still releasing P. During exchange 3 at P spike concentration of 0.13 mg L1 Sedment EPC T2 and T3 began retaining P while at exchange 4 and 5 all transects are retaining P. w values were obtained by plotting P release with floodwater spike concentration as shown in Figure 57. The EPCw values for WPB canal sediments from T1 to T4 were 0.021, 0.078, 0.094 and 0.052 mg L1 (Table 54). Among WPB canal transects, T1 had the least EPC value while T3 had the highest EPC value which reflects higher P release in T1 compared to T3 as indicated by the P release curves of WPB canal. The EPCw values of WPB canal sediments were lower than that of Miami canal sediments at all transects except T4 of Miami canal. Miami canal T4 consisted of sediments with high bulk density, high pH and very low organic matter, i.e. the sediments were mineral in nature which may have prevented P release leading to low EPCwAs evidenced by the data there were some striking differences between EPC values determined by adsorption studies and incubation of intact cores. In contrast to Miami canal sediments, the EPC values determined by intact sediment cores from WPB canal were similar compared to that by adsorption isotherm. values.

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142 5.4.1.3 P hosphorus release and EPCwThe EPC w values were found to be positively correlated with sedi ment P release values for all canals. Phosphorus released from WPB canal was lower than that of Miami canal sediments at all transects and the P release values for T1, T2 and T3 were 12.4, 16.1, 7.6, mg m2 (Figure 5 8). Transect 4 had the least P release (2.7 mg m2) value among WPB transects. Phosphorus retained by WPB canal sediments were higher than the P release values at all transects and the values were 98.4, 42.8, 58.1 mg m2 and 107.4 mg m2 for T1, T2, T3 and T4 respectively. High P r elease values resulted in higher EPCw values at T1, T2, T3 and least EPCw 5.5.1 Ocean Canal value at T4. Low P release values from WPB canal sediments were also observed in the incubation experiment (Chapter 4, Figure 46) Though WPB canal had similar sediment physicochemi cal properties as Miami canal, the low P release was thought to be due to the distribution of the carbonate layer that were effectively retaining P released from the sediments. 5.5.1.1 Batch adsorption isotherm Linear adsorption isotherm on Ocean canal sediments yielded EPC values of 0.07 mg L1at T1 (Figure 59). The EPC values of T2 to T4 were 0.66, 0.11 and 0.09 mg L1 (Table 55). Transect 2 of Ocean canal had the highest EPC value within Ocean canal sediments as well as all the canals The k values of transects T1, T3 and T4 were 37.5, 31.9 and 33.9 L kg1. The least k value was observed at transect T2 (15.7 L kg1). The k values are an indicator of the bonding energy of the soil for P and an increase in k indicates an increase in bonding energy and vice versa (Olsen and Watanbe, 1957).

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143 The low k value at T2 indicates very low bonding energy for P which may have facilitated P release from soils and resulted in high EPC05.5.1.2 Incubation of intact sediment cores value. Phosphorus release from Ocean canal sediments show that during exchange 1 with P spike concentration of 0.007 mg L1 all transects were releasing P (Figure 510). In exchange 2 with P spike concentration of 0.05 mg L1 T2 T4 are releasing P while the P release curve for T1 intersects the horizontal axis which indicates its equilibrium concentration. During exchange 3 with P spike concentration 0.12 mg L1 all transects were retaining P except T2 which briefly released P before finally starting to retain P. Thus the EP CwThe EPC for T2 T4 was expected to be between spike concentration of exchange 2 and exchange 3. At exchange 4 and 5 all the transects were retaining P. w values were determined by plotting P released/retained against the water column SRP concentration. Oc ean canal T1 yielded EPCw value of 0.05 mg L1 (Figure 5 11). The EPC values of T2 to T4 were 0.127, 0.084 and 0.071 mg L1There were differences between EPC values determined by adsorption study and incubation sediment cores. Similar to WPB canal P release in Ocean canal is very low thus EPC determined by both methods are similar except in T2. The high EPC (Table 5 6). 05.5.1.3 P hosphorus release and EPC value in T2 was most probably due to P released due to shaking but was not subject to diffusive P release during incubation experiment. wPhosphorus released from Ocean canal T1, T2 T3 and T4 were 2.8, 44.9, 20.7, and 21.2 mg m 2 (Figure 512). High er P release from Ocean canal T2 compared to the rest of the transects gave rise to high EPCw values among t he transects. Total P

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144 retained by both Miami and WPB canal sediments were higher than total P released by the sediments. Total P retained by Miami canal sediments were 79.8, 41.8, 70.3 and 87.3 mg m25.6.1 EPC for transects T1, T2, T3 and T4 respectively. 0, EPCw, k, SmaxMetal oxides such as Fe, Al, Ca and Mg provide positively charged surfaces that can bind P and influence sediment EPC and Sediment P roperties 0 and EPCw. Sediment EPC0 values were not significantly correlated with the metal concentrations but EPCw values were significantly correlated with Al, Ca and Mg concentrations (Table 57) which indicates that P from these metals influence the EPCw values in EAA canal sediments. Sediment k values were significantly correlated with the Fe, Al and M g concentrations. Sediment EPCw and EPC05.4 Conclusions values similar to sediment P release (Chapter 4, Table 41 and 42 ) were not correlated to sediment physicochemical properties including BD, %LOI and pH (Table 58) and different P fractions (Table 59) Sediment P release potentials affect EPC values determined by adsorption isotherms and incubation experiments. The EPC values determined by incubation experiments have been found to be higher than those determined by adsorption isotherms that w as due to the reducing conditions developed over the period of the experiment (a total of 35 days) that promote P release in sediment cores. Though the incubation experiments were conducted with a water column that was maintained in aerobic condition by bubbling water through it, according to Bostrom et al. (1982) oxygenated water has a redox potential of around +500 mV. But this redox potential decreases rapidly and at sediment depth of 1cm the redox potential and oxygen concentration can be about 200 mV and 0.1 mg L1 (Bostrom et al., 1982). Both

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145 methods yield similar EPC values when P release from sediments are low, which is particularly true for calcareous sediments (Chapter 3) for Miami canal T4 and Ocean canal sediments. The high EPC0 value at Ocean canal T2 was thought as a consequence of very low k or bonding energy value that aided P release. Similar EPCw and EPC0 values for WPB canal sediments were observed due to low EPCw values. This decrease in EPCw values for WPB canal that was thought to occur as a result of the distribution of calcium carbonate layers thereby preventing P release (Chapter 4) which could also be the reason of the high k values (from adsorption isotherm experiment) among all the canals. Similar to Ocean canal T2, EPC0 value of WP B canal T4 was very high than the rest of the transects and could be due to the very low bonding energy of the P in the sediments promoting P release. Thus future research is needed for the analysis of EPC values of these canal sediments using in situ tech niques.

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146 y = 750.32x + 26.093 R = 0.97 45 40 35 30 25 20 15 10 5 0 5 0.00 0.02 0.04 0.06 0.08 0.10 Equilibrium P Concentration. (mg L 1 ) EPC0=0.03 mg L1 Figure 51 Determination of EPC0 from linear adsorption isotherm for Miami canal, T1. Table 51 Equilibrium Phosphorus Concentrations (EPC0) from adsorption isotherms, maximum sorption capacity (Smax ) and intensity of adsorption (k) for Miami canal T1, T2, T3 and T4 sediments. Canal Transect EPC0 (mg L1) Equation R2 (%) Smax (mg kg1) Intensity of adsorption k (L kg 1 ) Miami T1 0.03 y = 750.32x + 26.093 97 667 250 T2 0.03 y = 1004.9x + 28.222 93 714 357 T3 0.06 y = 214.03x + 9.9754 77 909 179 T4 0.05 y = 1605.9x + 82.112 89 1110 179

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147 50 40 30 20 10 0 10 20 30 40 50 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 P mass release (mg m 2 ) Time (days) T1 T2 T3 T4 1stexchange (P spike 0.007 ppm 0 7 days) 2ndexchange (P spike0.05 ppm 0 7 days) 5thexchange (P spike0.35 ppm 0 7 days) 3rdexchange (P spike0.13 ppm 0 7 days) 4thexchange (P spike0.27 ppm 0 7 days) Figure 52 Cumulative P release from Miami canal T1T4 sediments during exchanges 15.

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148 y = 17.332x + 2.1424 R = 0.9668 5.0 4.0 3.0 2.0 1.0 0.0 1.0 2.0 3.0 0.0 0.1 0.2 0.3 0.4 P released/ retained (mg m 2 d 1 ) Spike concentration (mg L 1 ) EPCw=0.12 mg L1 Figure 53 Determination of EPCw of Miami canal T1 from sediment core incubation study. Table 52 Equilibrium Phosphorus Concentrations (EPCwCanal ) from sediment column incubation study for Miami canal T1, T2, T3 and T4 sediments. Transect EPCw (mg L1) Equation R 2 (%) Miami T1 0.12 y = 17.332x + 2.1424 97 T2 0.16 y = 23.824x + 3.7976 99 T3 0.12 y = 26.869x + 3.3678 98 T4 0.07 y = 15.358x + 1.1516 98

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149 180 140 100 60 20 20 60 100 140 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 Time (days) T1 T2 T3 T4 1stexchange, 0 7 days P spike 0.007 ppm 2ndexchange P spike 0.05 ppm, 714 days 5thexchange P spike 0.35 ppm, 2735 days 3rdexchange P spike 0.13 ppm, 1421 days 4thexchange P spike 0.27 ppm, 2127 days Total P released/retained (mg m2) Figure 54 Total P released and retained from Miami canal T1T4 sediments during exchanges 15.

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150 y = 61.4x + 1.4 R = 0.77 10 8 6 4 2 0 2 0.00 0.05 0.10 0.15 0.20 P released/ retained (mg kg 1 ) Equilibrium P Concentration (mg L 1 ) EPC0=0.02 mg L1 Figure 55 Determination of EPC0 from linear adsorption isotherm for WPB canal T1. Table 53 Equilibrium Phosphorus Concentrations (EPC0) from adsorption isotherms, maximum sorption capacity (Smax ) and intensity of adsorption (k) for WPB canal T1, T2, T3 and T4 sediments Canal Tra nsect EPC0 (mg L1) Equation R2 (%) Smax (mg kg1) Intensity of adsorption k (L kg1) WPB T1 0.02 y = 61.464x + 1.4581 77 1430 556 T2 0.04 y = 1179.2x + 43.26 90 1250 500 T3 0.04 y = 131.82x + 4.5003 98 769 278 T4 0.36 y = 31.382x + 11.473 85 1110 15.4

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151 0 5 10 15 20 25 30 35 40 45 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 P mass release (mg m 2 ) Time (days) T1 T2 T3 T4 1stfloodwater exchange (028 days) 2ndfloodwater exchange (2956 days) 3rdfloodwater exchange (5784 days) Figure 56 Cumulative P release from WPB canal T1T4 sediments during exchanges 15.

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152 y = 10.391x + 0.5445 R = 0.9295 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0.5 1.0 0.00 0.10 0.20 0.30 0.40 P released/ retained ( mg m 2 d 1 ) Spike concentration (mg L 1 ) EPCw=0.05 mg L1 Figure 57 Determination of EPCwTable 54 Equilibrium Phosphorus Concentrations (EPC for WPB canal T1 from sediment core incubation study. w ) from sediment column incubation study for WPB canal T1, T2, T3 and T4 sediments. Canal Transect EPCw (mg L1) Equation R2 (%) WPB canal T1 0.05 y = 10.391x + 0.5445 93 T2 0.09 y = 9.2333x + 0.8656 87 T3 0.08 y = 9.2317x + 0.7240 89 T4 0.02 y = 10.617x + 0.2206 95

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153 120 100 80 60 40 20 0 20 40 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 Time (days) T1 T2 T3 T4 1stexchange P spike 0.007 ppm, 07 days 2ndexchange P spike 0.05 ppm, 714 days 5thexchange P spike 0.35 ppm, 2735 days 3rdexchange P spike 0.13 ppm, 1421 days 4thexchange P spike 0.27 ppm, 2127 days Total P released/retained (mg m2) Figure 58 Total P released and retained from WPB canal T1T4 sediments during exchanges 15.

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154 y = 47.353x + 3.6747 R = 0.98 16 14 12 10 8 6 4 2 0 2 4 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 P released/ retained ( mg kg 1 ) Equilibrium P Concentration (mg L 1 ) EPC0=0.08 mg L1 Figure 59 Determination of EPC0 from linear adsorption isotherm for Ocean canal T1. Table 55 Equilibrium Phosphorus Concentrations (EPC0) from adsorption isotherms, maximum sorption capacity (SmaxCanal ) and intensity of adsorption (k) for Ocean canal T1, T2, T3 and T4 sediments. Transect EPC0 (mg L1) Equation R2 (%) Smax (mg kg1) Intensity of adsorption k (L kg1) Ocean T1 0.08 y = 47.353x + 3.6747 98 189 37.5 T2 0.66 y = 30.328x + 19.985 99 175 15.7 T3 0.11 y = 91.041x + 9.8118 94 256 31.9 T4 0.09 y = 55.389x + 4.8051 80 196 33.9

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155 30 20 10 0 10 20 30 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 P mass release (mg m 2 ) Time (days) T1 T2 T3 T4 1stexchange (P spike 0.007 ppm 0 7 days) 2ndexchange (P spike0.05 ppm 0 7 days) 5thexchange (P spike0.35 ppm 0 7 days) 3rdexchange (P spike0.13 ppm 0 7 days) 4thexchange (P spike0.27 ppm 0 7 days) Figure 510. Cumulative P release from Ocean canal T1T4 sediments during exchanges 15.

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156 y = 8.5204x + 0.426 R = 0.8938 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0.5 1.0 0.0 0.1 0.2 0.3 0.4 P released/ retained ( mg m 2 d 1 ) Spike concentration (mg L 1 ) EPCw=0.05mg L1 Figure 511. Determination of EPCw for Ocean canal T1 from sediment core incubation study. Table 56 Equilibrium Phosphorus Concentrations (EPCwCanal ) from sediment column incubation study for Ocean canal T1, T2, T3 and T4 sediments. Transect EPCw (mg L1) Equation R2 (%) Ocean canal T1 0.05 y = 8.5204x + 0.426 89 T2 0.13 y = 8.5251x + 1.0834 87 T3 0.08 y = 10.615x + 0.8906 94 T4 0.07 y = 12.955x + 0.9164 97

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157 100 80 60 40 20 0 20 40 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 0 2 4 7 Time (days) T1 T2 T3 T4 1stexchange P spike 0.007 ppm, 07 days 2ndexchange P spike 0.05 ppm, 714 days 5thexchange P spike 0.35 ppm, 2735 days 3rdexchange P spike 0.13 ppm, 1421 days 4thexchange P spike 0.27 ppm, 2127 days Total P released/retained (mg m2) Figure 512. Total P released and retained from Ocean canal T1T4 sediments during exchanges 15.

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158 Table 57 Correlation between sediment metal (Fe, Al, Ca and Mg) and EPC0, EPCw, k and Smax Table 58 Correlation between sediment physicochemical properties with EPC0 and EPCw Table 59 Correlation between sediment EPC0 and EPCw with sediment P fractions, total P and P released from intact sediment study. Significant at the 0.05 probability level ** Significant at the 0.01 probability level *** Significant at the 0.001 probability level ns Not significant Fe mg kg 1 Al mg kg 1 Ca mg kg 1 Mg mg kg 1 EPC 0 ( mg L 1 ) 0.04 ns 0.04 ns 0.3 ns 0.09 ns EPCw ( mg L 1 ) 0.56 ns 0.69 0.62 0.63 k ( L kg 1 ) 0.88 *** 0.73 0.06 ns 0.65 S max ( mg kg 1 ) 0.38 ns 0.16 ns 0.64 0.07 ns BD LOI pH EPC 0 0.29 ns 0.12 ns 0.57 ns EPC w 0.27 ns 0.1 ns 0.04 ns Labile P NaOH Pi NaOH Po HCl P Res P Total P P released EPC 0 0.23 ns 0.45 ns 0.50 ns 0.30 ns 0.34 ns 0.42 ns EPC w 0.02 ns 0.07 ns 0.06 ns 0.02 ns 0.02 ns 0.04 ns 0.82***

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159 CHAPTER 6 SUMMARY AND CONCLUSIONS The Everglades Agricultural Area (EAA) is lo cated in South Florida between l ake Okeechobee and the Everglades National Park. Nutrient enrichment from the EAA particularly phosphorus ( P ) is thought to be responsible for the ecosystem changes in the Everglades. Best Management Practices (BMP) in the EAA were implemented since 1995 to reduce the P loads. Despite the success of the BMPs, there are concerns about accumulated sediments in the canals of the EAA that can be a potential P source to the overlying water column affecting the water quality in downstream ecosystems. I nvestigation into the ph ysicochemical properties of farm and main EAA canal s, potential extent of P release, factors res ponsible for release from the sediments may further improve BMP performance and implementation. F arm canals receive drainage water directly from agricultural fields. M ain canals receive irrigation from farm canals in addition to flow through water from lak e Okeechobee. 6.1 Total Phosphorus S torage in Farm Canals Our first objective was to investigate the physicochemical pr operties and P fractions in farm canals. Farm canals receive drainage water directly from farms investigations into these sediment properties could reveal important information about P storage, and efficiency of the canal management practices in controlling P storage in these canals. Our investigations into sediment P storage in farm canal s ediments revealed that sediment physicochemical properties and P storage were largely influenced by canal management practices. All farm canals are managed by farm owners to control dissolved and particulate P export but canal 06AB had management practices that include controlling floating aquatic vegetation and regular canal sediment

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160 cleaning. W e found 06AB sediments to have dominant mineral properties including higher bulk density, higher pH and lower organic mat ter than 09A and 00A canals, which reflects less contribution of floating aquatic vegetation into sediment accumulation. E verglades A gricultural A rea canals were originally dug until the calcium carbonate bedrock and the sediments in the canal are the result of accumulation of particulates over tim e from the farms ( Gleason and Spackman, 1974) A major portion of the sediments in EAA farm canals come from biological contribution i.e. floating aquatic vegetation (Stuck, 1996). Thus dominant mineral matter contribution indicates that canal 06AB has dir ected its management operations well which has countered particulate accumulation. The lower accumulation of particulates in canal 06AB also resulted in lower total P content in sediments compared to 09A and 00A. Estimation of 09A, 00A and 06AB canal area and volume were made by Google map, 2010 as described in Appendix D Total P stored in these farm canals ranged from 0.2 to 0.4 metric tons (Table 61) Higher P storage in farm canals 09A and 00A than canal 06AB also indicate the effectiveness of the ma nagement practices in ca nal 06AB that resulted in lower P storage. Estimation of P storage in other farm canals could not be made as there are hundreds of farm canals spread across the EAA like web and quite difficult to get an estimation of the area cover ed by the farms using Google Earth. 6.2 Total Phosphorus S torage in Main Canals Our next objective was to characterize the main canal s that receive water from the farm canals and lake Okeechobee. Main canals are larger than farm ca nals in terms of length, width and depth. Main canals are managed by SFWMD and in contrast to farm canals no routine management practices are performed on the main canals except spraying chemicals to control floating aquatic vegetation. In comparison to the farm

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161 canals physicoche mical properties of main canal reflected the geology of the area. Ocean canal sediments are mineral in nature with higher bulk density, higher pH, and lower total P content compared to Miami and WPB canal sediments ( see chapter 3, Table 3 2 and Table 34 ) Both Miami and WPB canal s were situated in lower geological terrains (Fort Thomson formation), whereas Ocean canal was situated in higher bedrock formations ( Anastasia formation) ( USGS, Figure 3.1) The areas of the main canals were calculated similar to farm canals and t he volume of the sediments at depth 05 cm was calculated. T o tal P stored in Miami, WPB and O cean canal sediments till depth 5 cm were 175, 2 5 .4, and 7 1 1 MT respectively The P storage values for the farm canals were an order of magnitude lower than main canals, which are due to smaller area and resultant lower volume of the farm canals Phorphorus storage values indicated that large quantities of P are stored in EAA canals that could function as a P source to the system. Thus P fractionation was important to understand the reactivity and recalcitrance of the total P storage. 6.3 P hosphorus Fractions The distribution of different P fractions in the farm and main canals were similar. The HCl ext ractable P was the dominant fraction with 59% to 70% of total P followed by residueP fraction (17% to 34% of total P) ( see chapter 2, Figure 2 2 and 3 3 ) This indicates that the majority of the inorganic P compounds in both these canals exist as bound to Ca and Mg which are generally considered as stable. Mineralogical analysis did not detect any P containing mi nerals, which denotes one of two possibilities that e ither apatiteP is absent in canal sediments or apatite P concentration is b e low detectable limit. In both possibilities HCl P can release P. Though the pH values in the main canal sediments are around 7, there can be diel fluctuations in pH resulting from

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162 macrophyte and algae respiration causing enough acidity to hydrolyze HCl P in sediment microzones ( Carlton and Wetzel 1987 ; Mortimer, 1941, 1942). Organic P in both farm and main canals constituted about 13 and 6% respectively of total P that is in contrast to high organic P content in the STAs, the WCAs and the ENP ( Qualls and Richardson, 1995; Reddy et al., 1998). This is believed to be due to the unique hydrology in the downstream ecosystem that facilitates accumulation of organic particulates which has lower mineralization rates due to wetland conditions ( Qualls and Richardson, 1995; Reddy et al., 1998). The residueP was the second highest P fraction in both farm and main canals that is generally thought to represent recalcitrant organic P Thus t he contribution of different P fractions towards P release is subject t o further analysis, which was our next experiment. 6.4 Phosphorus Release from EAA Main Canals Our third experiment was to determine the P release characteristics of sediments from three main canals of EAA: Miami Canal, West Palm Beach Canal (WPB) and Ocea n Canal. Only main canal sediments were chosen for the experiment as farm canals ultimately drain into the main canals, which transport water to the downstream ecosystems. It was hypothesized due to years of P loading these canals can now act as a P sour c e through internal loading Best management practices in EAA reduce dissolved and particulate P from the farms but there are no management practices for the main canal s. T he knowledge of main canal P release potential could be helpful in setting management policies for these sediments. A ll canals released P through a period of 84 days when sediments were incubated with low P concentration water that represents the downstream Everglades P concentrations but the magnitude of P released varied between canals ( see chapter 4,

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163 Figure 4 2 Figure 4 5 and Figure 48 ) Under field conditions with continuous addition of P, release of P can continue for a long time until further addition has been stopped and all the P sources are exhausted ( Larsen et al., 1979; Ryding, 1981) Phosphorus release from Miami canal was higher than both WPB and Ocean canal sediments though the sediment total P values were similar in Miami and WPB canal s. Using P release data, total internal P loading from the entire canal was estimate d by multiplying release values by canal area (Table 62, Table 63 and Table 64). Though P release from Miami canal was higher than both WPB and Ocean canal, the estimated total P released from the entire surface area of WPB canal had higher values at T1, T2, T3 notably due to great er canal area than Miami canal. Phosphorus release from the EAA main canals were significantly correlated with total P concentrations which explains the low P release from Ocean canal sediments that had the lower total P concentrations (Table 4 3 ) than Miami and WPB canal The different P fractions were not significantly correlated with P release. B ut the fact that P release was significantly correlated with total P led us to the conclusion that all P fractions ma y be contributing to P release and a complex combination of various factors were in effect in the canals. Similar correlation of P release with total P from sediments have been observed in eutrophic lake Alserio, (Italy), hypereutrophic lake Arungen (Norwa y), mesotrophic lake Balaton (Hungary), and oligotrophic lake Crystal (Minnesota) (Premazi and Provini, 1985; Graneli, 1979; Bostrom and Petterson, 1982; Messer et al., 1983). From the studies researchers concluded that in addition to reactive P, P fractio ns that were previously considered as non releasable or refractory were also contributing to P fluxes from sediments.

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164 Miami, WPB and Ocean canals were different between each other in terms of not only physicochemical properties but also canal depth and spatial d istribution of carbonate layers (Figure 6 1, 6 2 and 63). Miami canal is situated in a low geological terrain, had higher total P concentration (1430 mg kg16.5 Internal P loading from EAA Main Canal Sediments ) and total P storage (175 kg) in the top 05 cm layer than WPB and Ocean canal sediments West Palm Beach canal contained interspersed carbonate layers that was most probably responsible for lower total P storage (2 5 .4 kg) than Miami canal. In addition, the carbonate layers in WPB canal were thought to inhibit P release from sediments. Ocean canal sediments had dominant mineral properties with lower total P values among the three canals and also lower P release. D ept h measurements conducted during sampling indicated that Ocean canal was a shallow canal with a layer of coarse shell and limestone rock fragments on sediment surface. Thus not only the chemical composition of sediment P but also the spatial distribution of sediment may control P release in EAA canals. Estimates of annual internal P loads from EAA main canal sediments (Table 62; Table 63 ; Table 64) were made using cumulative P release data (Chapter 4). The annual P internal load estimates were made by multiplying the P release values by the canal areas for exchanges 1, 2 and 3 r espectively. The detailed calculation of the internal P load derivation is provided in Appendix G. The average annual internal P load over exchanges 1, 2 and 3 for Miami, WPB and Ocean canal are provided in Table 65. Our estimation show that annual internal P load from Miami canal can vary from 0.2 to 0.8 MT, while WPB canal internal P loads can vary from 0.1 to 0.4 MT and Ocean canal internal P loads can vary from 0.1 to 0.2 MT. Comparison of EAA canal internal P load to the P load from the EAA of 129 MT in water year 2009 (SFER 2010a ) shows that the

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165 internal P load is a very small portion of the entire P load from EAA. But it has to be recalled that the internal P load calculated here takes into account diffusive P flux only. I n reality P flux from EAA c anals can be much higher than the calculated value due to sediment transport and resuspension. Water flow in EAA canals are controlled by pumps and undergo rapid fluctuations from stagnant conditions to very high velocity that can cause resuspension and sediment transport Sediment resuspension has been reported to cause about 20 to 30 times greater P release than undisturbed sediments ( Sondergaard et al., 1992). Particularly it was observed that bioturbation and resuspension caused higher P flux in calcareous lake sediments compared to noncalcareous lake sediments (Graneli, 1979). 6.6 Equilibrium Phosphorus Concentrations Following the determination that the main canal sediments potentially can function as P sources our fourth experiment aimed to determine the limit of P concentrations that determines the function of the sediment as P source or sink i.e. the equilibrium P concentration or EPCw values of the canal sediments The mean EPCw values for Miami canal sediments determined by intact sediment columns were 0.120.03 mg L1, for West Palm Beach canal 0.060.03 mg L1 and Ocean canal 0.080.03 mg L1. The EPCw values reflected the P release patterns of the canals observed from canal sediments in our third experiment. Canals with higher P release values had higher EPCw values than canals with lower P releases Thus higher P releases in Miami canal sediments resulted in higher EPCw values than WPB and Ocean canals. Comparison of the EPCw values with water column SRP concentrations (Table 66 ) of the canals indicated that Miami canal T1, T2, T3 and Ocean canal T2 were acting as P sources to the water column.

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166 6.7 Conclusions Everglades Agricultural Area canal sediments are an important part of the entire Everglades system but there was not eno ugh information on this part of the ecosystem compared to the STAs, WCAs and the ENP. Physicochemical properties indicated that organic matter content varied from 2070% and the sediments had very low bulk density due to which, they are susceptible to transport to the P limited ecosystems in the south. Though sediment samples contained considerable organic matter, organic P fraction accounted just about 6 13% of total P. This is in contrast to the wetland sediments of the STAs, WCAs and the ENP where sedime nt hydrology promotes P sequestration and consequently has higher organic P content. Dissolved organic P content in the Everglades (Qualls and Richardson, 2003) is a point of concern but our studies showed that inorganic P comprised majority (96%) of the P released. Though the individual P frac tions varied between canals, the percent distribution of the different fractions were similar with HClP and ResidueP being the largest P fractions comprising almost 80 90% of total P Phosphorus release from EAA canal sediments was not correlated with different P fractions but was significantly correlated with total P. Thus we speculate that all P fractions were contributing to P release and a complex interaction of various factors was in effect in the canals. However P internal P load estimates from the canals were a very small portion compared to total EAA P load. This internal P load from the canals was an estimate of the diffusive P flux only as this research did not consider sediment transport and resuspension impacts on P release. Sediment EPCW values suggested portions of the canals were functioning as a P source to the water column. Further studies are necessary to estimate internal P loading from the canal sediments with water v elocity, sediment transport and resuspension as some of the factors.

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167 The EAA main canals are the interface between the nutrient enriched EAA and the STA filter marshes (Figure 6 4) The STAs filter the inflow water through P uptake and sedimentation. Inflo w water concentrations to the STAs in water year 2009 (SFER, 2010a ) were recorded as 182, 246, 122, 96, 254 and 264 g L1 for STA 1E, 1W, 2, 5 and 6 respectively T he outflow concentrations were recorded as 21, 26, 18, 13, 56 and 93 g L1 for STA 1E, 1W, 2, 5 and 6 respectively The STAs require regular maintenances and periodic rehabilitation of the marshes. Management practices within the main canals can result in reduced inflow concentrations and P load to the STAs that can boost STA performance and increase its longevity. This could lead to a reduction in cost of STA rehabilitation and most importantly can get closer to the target P concentrations of 10 ppb in the Everglades Management practices in the canals can include periodic dredging the st retch of canals particularly at portions of Miami canal and Ocean canal. In addition to dredging berming the canal banks can prevent the accumulation of particulate P into the canals Thus management of P concentrations in the outflow from the EAA main canals can be a key component in maintaining oligotrophic nutrient status in the Everglades.

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168 Table 61 Estimation of total P storage in EAA main (Miami, WPB, Ocean) and farm (09A, 00A, 06AB) canal sediments. Canal Total P mg kg1 BD g cm3 Total P mg cm3 Area m2 Sediment volume till 5 cm depth cm 3 Total P stored (total P x volume) mg Total P stored MT 09A 794 0.19 0.15 5.56x10 4 2.78x10 9 4.20x10 8 0.4 00A 1520 0.12 0.18 3.67x10 4 1.83x10 9 3.35x10 8 0.3 06AB 576 0.37 0.21 2.10x10 4 1.05x10 9 2.24x10 8 0.2 Miami 1430 0.26 0.37 9.45x10 5 4.72x10 10 1.75x10 11 175 WPB 1130 0.22 0.25 2.03x10 6 1.02x10 11 2.54x10 10 25.4 Ocean 590 0.35 0.21 6.89x10 5 3.44x10 10 7.11x10 9 7.11

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169 Figure 61 Schematic representation of P release from a section of Miami canal sediments

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170 Figure 62 Schematic representation of P release from a section of WPB canal sediments

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171 Figure 63 Schematic representation of P release from a section of Ocean canal sediments

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172 Table 62 Estimation of annual internal P loading from Miami canal exchanges 1, 2 and 3. Exchange 1 Excha nge 2 Exchange 3 Miami canal Cumulative P release in 28 days Cumulative P released from canal /year Cumulative P release in 28 days Cumulative P released from canal /year Cumulative P release in 28 days Cumulative P released from canal /year mg m2 MT mg m2 MT mg m2 MT T1 31.9 0.4 35.6 0.4 18.9 0.2 T2 108 1.3 70.5 0.9 16.7 0.2 T3 86.9 1.1 77.1 0.9 18.7 0.2 T4 37.0 0.5 18.8 0.2 4.89 0.1 Table 63 Estimation of annual internal P loading from WPB canal exchanges 1, 2 and 3. Exchange 1 Exchange 2 Exchange 3 WPB canal Cumulative P release in 28 days Cumulative P released from canal /year Cumulative P release in 28 days Cumulative P released from canal /year Cumulative P release in 28 days Cumulative P released from canal /year mg m 2 MT mg m 2 MT mg m 2 MT T1 31.2 0.8 9.74 0.3 9.40 0.2 T2 28.1 0.7 9.01 0.2 6.04 0.2 T3 26.5 0.7 17.7 0.5 10.34 0.3 T4 6.90 0.2 3.00 0.1 2.94 0.1

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173 Table 64 Estimation of annual internal P loading from Ocean canal sediments during exchanges 1, 2 and 3. Exchange 1 Exchange 2 Exchange 3 Ocean canal Cumulative P release in 28 days Cumulative P released from canal /year Cumulative P release in 28 days Cumulative P released from canal /year Cumulative P release in 28 days Cumulative P released from canal /year mg m 2 MT mg m 2 MT mg m 2 MT T1 24.2 0.8 5.21 0.3 4.62 0.2 T2 43.1 0.7 18.9 0.2 9.31 0.2 T3 21.9 0.7 18.8 0.5 4.78 0.3 T4 20.6 0.2 13.2 0.1 7.42 0.1 Table 6 5 Estimation of an nual internal P loading from Miami, WPB and Ocean canal sediments over exchange 1, 2 and 3. Miami canal Mean cumulative P released from canal /year over exchanges 1, 2 and 3 WPB canal Mean cumulative P released from canal /year over exchanges 1, 2 and 3 Ocean canal Mean cumulative P released from canal /year over exchanges 1, 2 and 3 MT MT MT T1 0.4 T1 0.4 T1 0.1 T2 0.8 T2 0.4 T2 0.2 T3 0.8 T3 0.5 T3 0.1 T4 0.2 T4 0.1 T4 0.1

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174 Table 66 Comparison of EPCw and SRP concentrations of Miami, WPB and Ocean canal sediments Miami canal WPB canal Ocean canal Transect EPCw (mg L1) Water column SRP (mg L1) EPCw (mg L1) Water column SRP (mg L1) EPCw (mg L1) Water column SRP (mg L1) T1 0.12 0.03 0.05 0.06 0.05 0.06 T2 0.16 0.03 0.09 0.06 0.13 0.07 T3 0.12 0.03 0.08 0.05 0.08 0.07 T4 0.07 0.05 0.02 0.06 0.07 0.06 P enriched waterCanal P concentrations to the STAs (ppb) (SFER, 2010): STA 1E -182 STA 1W -246 STA 2 -122 STA -96 STA 5 -254 STA 6 -264 STAs function by: P uptake Reduction of SRP Reduction of particulate P by sedimentation Out flow P concentrations from STAs (ppb) (SFER, 2010): STA 1E -21 STA 1W -26 STA 2 -18 STA -13 STA 5 -56 STA 6 -93 Target concentration-10 ppb Periodic STAs maintenances Dredging and rehabilitation Reduction in dissolved and particulate P in main canals can lead to: Reduced inflow concentrations to STAs Prolong STA longevity Reduced cost for STA rehabilitation Reduced load can enhance STA performance Possibly can get outflow concentrations closer to target concentrations Lake Okeechobee Farms Farm Canals Main Canals STAs WCAs and Downstream P Limited Ecosystems Figure 64 Water and nutrient flow through the Everglades system.

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175 APPENDIX A INORGANIC P FRACTION ATION An inorganic fractionation scheme was used to determine the main P factions in the sediments of main district canals and typical farm canals in the EAA. Inorganic P fractionation was determined by sequential extraction (Hieltjes and Lijklema. 1980, Reddy et al., 1998). The sediment was prepared by weighing the wet weight equivalent of 0.3 g of dry sediment into previously weighed 50 ml polypropylene centrifuge tubes. The KCl Pi content of the sediment was determined by adding 30 mL of 1.0 M KCl and agitating on a mechanical shaker for 2 h. The suspensions were then centrifuged at each tube were collected in labeled 50 mL scintillation vials. The weight of the centrifuge tube, sample and KCl residue was again recorded after filtration. The filtrates were stored at 4oThe filtrates were stored at 4 C and analyzed for SRP using a Spectrophotometer within 30 days after collection (EPA Method 365.1, 1 993).The NaOH Pi and the NaOH P contents of the sediment were determined by extraction with 30 mL of 0.1 M NaOH on a mechanical shaker for 17 h centrifugation at 8000 rpm for 15 minutes, and vacuum filtration (0.45 m) into prelabeled 50 mL scintillation vials. oTo analyze for NaOH P, 5 mL of each filtrate was pipetted into a labeled 250 mL conical flasks and treated with 1 mL of 11 N sulfuric acid and 0.4 g of potassium C and analyzed for extractable Pi and digested for total P. To analyze for NaOH Pi, 7 mL of each filtrate was pipetted into labeled centrifuge tubes and acidified with 7 drops of concentrated sulfuric acid (36 N). The acidified filtrates were centrifuged at 6000 rpm for 5 minutes. The supernatants were decanted and analyzed for SRP.

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176 persulfate. The samples were digested at 125oC for 3 hours and at 380oC for 4 hours. After cooling to approximately 100oThe HClPi (Ca bound P) content of the sediment was determined by adding 30 mL of 0.5 M HCl to each sample. The samples w ere then placed on a mechanical shaker for 24 h. After 24 hours the samples were centrifuged at 8000 rpm for 15 labeled 50 mL scintillation vials. The weight of the centrifuge tube wit h HCl residue was recorded after filtration. The filtrates were stored at 4 C, 10 mL of distilled water was added to each flask and shaken. The digests samples were analyzed for total P. T he Humic and Fulvic acid Po content of the sediment was calculated by subtracting the NaOH Pi (Fe/Al bound Pi) from the NaOH P values. oThe residue P content of the soil was determined utilizing the ignition method (Andersen, 1974). Samples were transferred from the centrifuge tube into a weighed and prelabeled 50 mL beakers using double distilled water. The samples were dried in an oven at 70 C and analyzed for SRP. oC until constant weight and the dry weights recorded. The beakers were then placed in a muffle furnace at 500 50oC for 4 hours then allowed to cool overnight. After cooling in the muffle furnace, the beakers were further cooled to room temperature and then weighed to determine loss on ignition. The ash was then moistened with double distilled water and 20 mL of 6 N HCl was added. The samples were then placed on a hot plate at 100120oC until dry, and then the temperature was set at high (260280oC) for 30 minutes. The samples were then removed from the hot plate and allowed to cool to room temperature followed by the addition of 2.25 mL 6 N HCl to each beaker. The samples were again put on the hot plate and just brought to a boil which occurs

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177 within a couple of minutes and removed. The filtrate from the ashed samples were transferred to 50 mL volumetric flasks after filtration and analyzed for total P.

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178 APPENDIX B E XTRACTABLE Fe AND Al The sediments were pretreated for CaCO3About 0.5 g of sediment was weighed out and to it was added 20 mL of ammonium oxalate solution (ph 3.0) in a centrifuge tube. The centrifuge tubes were shaken in a reciprocating shaker for 4 h. We s imulated dark conditions in the laboratory by wrapping the centrifuge tubes with Al foil and turning the lights off. Following shaking the tubes were centrifuged at 6000 rpm for 10 minutes. The supernatant was filtered entrations of Fe and Al in the extracts were determined using Inductively Coupled Plasma spectroscopy (ICP) (Spectro Analytical CIROS CCD). by placing 0.5 g of sediment in a 50 mL polypropylene centrifuge tube to which was added 30 mL of 1.0 M ammonium acetate solution. The solution was allowed to react for 1 h with intermittent stirring. The ph was measured and adjusted to 5.5 by dropwise addition of acetic acid. This was repeated hourly until the ph stays approximately constant. The resultant solution was centrifuged, decanted, and washed with deionized water to remove the dissolved Ca and acetate, and left to air dry.

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179 APPENDIX C EXTRACTABLE Ca AND Mg To 10 mL of sediment 25 mL of 0.5 N Acetic acid was added and left to react overnig ht (approximately 20 h). The samples were then shaken for 50 minutes on and endto end shaker. The samples were filtered using Whatman no. 5 filter paper and the filtrates collected. APPENDIX D ESTIMATION OF AREA AND VOLUME OF EAA CANALS Estimation of EAA farm and main canal length as well as width were done using Google maps, 2010. Width of the canal against a given unique latitude and longitude value, was calculated by the add path function and choosing meters as the unit of choice. The areas of canal s were obtained by multiplying the calculated canal length by canal breadth. Canal volume till 05 cm depth was calculated by multiplying canal area by required depth (5 cm). The total P storage at 05 cm depth was determined by multiplying total P content (mg kg1) of the canals by sediment bulk density (g cm3 ) and canal volume. Suitable unit conversions were performed on the calculations.

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180 APPENDIX E FIGURES Figure E 1 Inorganic P fractionation scheme. Figure E 2 Map of farm canal 09A. B. Sampling transects (T1T5) in farm canal 09A (Google Maps 2010 ). 0.1 M NaOH 17 h 0.5 M 24 h Ashed at 550oC 6 M HCl NaOH P o Fe Al bound NaOH Pi Ca Mg bound HCl P i Residue Recalcitrant P Readily available P KClP 2 h 1 M 0.3g dry weight equivalent Residue Residue Sediment Residue Pump Station LEGEND: Main Farm Canal Farm Canal Field Ditch N Miami Canal UF9209ACrop Planting LayoutMain Canal PumpX X X X X X XHydro Bridge =742.9 (371) Bridge Culv1 = 2510.3 (1255.15) Culv1 Culv2 = 2626.2 (1313.1) Culv2 Culv3 = 2655 (1327.5) Culv3 culv4 = 2699.7 (1349.85) Culv4 Culv5 = 2586.7 (1293.35) Culv5 End = 2469.7 (1234.85) Hydro Bridge C1 C2 C3 C4 C5 Booster Pump C# = Core # C#1 C#2 C#3 C#3A C#3B C#4 C#5 C#6 C#7 C#10 XC#11XC#9XC#8X X X A B

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181 Figure E 3 Map of farm canal 00A. B. Sampling transects (T1T5) in farm canal 09A (Google Maps 2010 ). Figure E 4 Map of farm canal 06AB. B. Sampling transects (T1T5) in farm canal 09A (Google Maps 2010 ). UF9206A/BCrop Planting Layout North Pump Station South Pump StationDischarge CanalAll field ditches are joined to the main farm canals and the perimeter ditches by culvert and riser connections not shown. NMain Canal Farm Canal Field Ditch LEGEND: Pump S.R. 880 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 A B 10-2Crop Planting LayoutMain Farm CanalUF9200A C01 C02 C03 C04 C05 C06 C07 C08 C09 C10 C11 C12 C13 C14 C15 NC01 NC02 NC03 NC04 NC05 NC06E NC07 NC08 NC09 NC10 NC11 NC12 NC13 NC14 NC15 NC06W 502 661 653X 682 667X 660 598 688 636 684 680 655 658 659 593 663X 581 659 658 678 661 663 660 636 638 334 705 715 658 590 652 661 322 500 X1 1000 X2 1500 X3 2000 X4 2571 2575 A B

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182 Figure E 5 Sampling transects (T1T4) in Miami canal (Google Maps 2010). Figure E 6 Sampling transects (T1T4) in WPB canal (Google Maps 2010).

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183 Figure E 7 Sampling transects (T1T4) in Ocean canal (Google Maps 2010).

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184 APPENDIX F LATITUDE AND LONGITU TE OF EAA FARM AND M AIN CANALS Table F 1 Latitude and longitud e values of farm canal 09A transects. Farm canal 09A No of reps taken Distance between transects (m) Breadth (m) Latitude Longitude T1 3 15.5 26.652727 80.822285 T2 3 209.3 12.1 26.649151 80.821188 T3 3 393.1 10.3 26.642188 80.821182 T4 3 410.3 7.7 26.634919 80.821152 T5 3 829.7 8.4 26.620222 80.820975 Length of farm canal 09A calculated: 5153 m Table F 2 Latitude and longitude of farm canal 00A transects Farm canal 00A No of reps taken Distance between transects (m) Breadth (m) Latitude Longitude T1 3 5.5 26.764664 80.506107 T2 3 292.2 6.0 26.761760 80.510928 T3 3 308.7 4.9 26.761770 80.517081 T4 3 302.7 8.0 26.761811 80.523113 T5 3 302.5 8.1 26.761823 80.529141 Length of farm canal 00A calculated: 5642 m Table F 3 Latitude and longitude of farm canal 06AB transects Length of farm canal 06AB calculated: 2786 m Farm canal 06AB No of reps taken Distance between transects (m) Breadth (m) Latitude Longitude T1 3 7.12 26.656609 80.467578 T2 3 279.7 6.8 26.656612 80.473144 T3 3 228.2 8.5 26.656593 80.477685 T4 3 203.6 8.4 26.656583 80.481737 T5 3 306.1 6.8 26.656578 80.487829

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185 Table F 4 Latitude and longitute values of Miami canal transects. Miami canal No of replicates Distance between transects (km) Breadth (m) Latitude Longitude T1 3 33.3 26.680715 80.814522 T2 3 11.0 26.8 26.625412 80.832570 T3 3 10.5 33.4 26.569312 80.843311 T4 3 10.9 32.6 26.511736 80.829634 Length of Miami canal calculated: 29900 m Table F 5 Latitude and longitude of WPB canal transects. WPB canal No of replicates Distance between transects (km) Breadth (m) Latitude Longitude T1 3 26.7 26.713937 80.431951 T2 3 10.5 23.8 26.750659 80.480423 T3 3 10.8 33.4 26.788199 80.530485 T4 3 10.5 36.5 26.825139 80.579180 Length of WPB canal calculated: 67600 m Table F 6 Latitude and longitude of Ocean canal transects. Ocean canal No of replicates Distance between transects (km) Breadth (m) Latitude Longitude T1 3 33.8 26.678580 80.441306 T2 3 2.4 28.3 26.678738 80.426682 T3 3 1.9 29.3 26.678612 80.414875 T4 3 1.9 39.7 26.678524 80.403063 Length of Ocean canal calculated: 21000 m

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186 APPENDIX G ESTIMATION OF ANNUAL INTERNAL P LOADING FROM EAA MAIN CANALS Table G 1 Estimation annual internal P loading from Miami canal exchange 1. Miami canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m 2 mg mg MT T1 31.9 3.01x10 7 3.93x10 8 0.4 T2 108 1.01x10 8 1.32x10 9 1.3 T3 86.9 8.21x10 7 1.07x10 9 1.1 T4 37 .0 3.49x10 7 4.56x10 8 0.5 Estimated area of Miami canal 9.45x105 m2. Table G 2 Es timation annual internal P loading from Miami canal exchange 2. Miami canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m 2 mg mg MT T1 35.6 3.36x10 7 4.39x10 8 0.4 T2 70.5 6.66x10 7 8.68x10 8 0.9 T3 77.1 7.29x10 7 9.50x10 8 0.9 T4 18.8 1.78x10 7 2.32x10 8 0.2 Estimated area of Miami canal 9.45x105 m2. Table G 3 Estimation annual internal P loading from Miami canal exchange 3. Miami canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m2 mg mg MT T1 18.9 1.79x107 2.33x108 0.2 T2 16.7 1.58x107 2.06x108 0.2 T3 18.7 1.77x10 7 2.30x10 8 0.2 T4 4.89 4.62x106 6.02x107 0.1 Estimated area of Miami canal 9.45x105 m2.

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187 Table G 4 Estimation annual internal P loading from WPB canal exchange 1. WPB canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m 2 mg mg MT T1 31.2 6.33x10 7 8.26x10 8 0.8 T2 28.1 5.70x10 7 7.44x10 8 0.7 T3 26.5 5.38x10 7 7.01x10 8 0.7 T4 6.90 1.40x107 1.83x108 0.2 Estimated area of WPB canal 2.03x106 m2. Table G 5 Estimation annual internal P loading from WPB canal exchange 2. WPB canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P r eleased from canal /year mg m 2 mg mg MT T1 9.74 1.98x10 7 2.58x10 8 0.3 T2 9.01 1.83x10 7 2.38x10 8 0.2 T3 17.7 3.59x10 7 4.68x10 8 0.5 T4 3 .00 6.09x106 7.94x107 0.1 Estimated area of WPB canal 2.03x106 m2. Table G 6 Estimation annual internal P loading from WPB canal exchange 3. WPB canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m 2 mg mg MT T1 9.40 1.91x10 7 2.49x10 8 0.2 T2 6.04 1.23x107 1.60x108 0.2 T3 10.34 2.10x107 2.74x108 0.3 T4 2.94 5.97x106 7.78x107 0.1 Estimated area of WPB canal 2.03x106 m2.

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188 Table G 7 Estimation annual internal P loading from Ocean canal exchange 1. Ocean canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m2 mg mg MT T1 24.2 1.67x107 2.17x108 0.8 T2 43.1 2.97x107 3.87x108 0.7 T3 21.9 1.51x107 1.97x108 0.7 T4 20.6 1.42x107 1.85x108 0.2 Estimated area of Ocean canal 6.89x105 m2. Table G 8 Estimation annual internal P loading from Ocean canal exchange 2. Ocean canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m 2 mg mg MT T1 5.21 3.59x106 4.68x107 0.3 T2 18.9 1.30x107 1.70x108 0.2 T3 18.8 1.30x107 1.69x108 0.5 T4 13.2 9.09x106 1.19x108 0.1 Estimated area of Ocean canal 6.89x105 m2. Table G 9 Estimation annual internal P loading from Ocean canal exchange 3. Ocean canal Cumulative P release in 28 days Cumulative P released in 28 days from entire canal Cumulative P released from canal /year Cumulative P released from canal /year mg m 2 mg mg MT T1 4.62 3.18x106 4.15x107 0.2 T2 9.31 6.41x106 8.36x107 0.2 T3 4.78 3.29x10 6 4.29x10 7 0.3 T4 7.42 5.11x106 6.66x107 0.1 Estimated area of Ocean canal 6.89x105 m2.

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210 BIOGRAPHICAL SKETCH Jaya Das was born in the city of Calcutta, India. She went to school at Bata Girls High School until 1996. Thereafter she was admitted to the presti gious University of Calcutta where she received her Bachelor in Science (B.Sc.) in c hemistry in 2000. She completed a Post Graduate Diploma in Computer Applications from the University of Kalyani in 2001. Thereafter she returned to University of Calcutta to complete her Master of Science (M.Sc) in agricultural chemistry and soil s cience in 2003. She decided to pursue higher studies and joined the Ph.D. program in the Soil and Water Science D epartment at U niversity of F lorida in fall of 2005 with Dr. Samira Daroub and Dr. George OConnor as her advisor s. Since then she has been engaged in research about nutrient dynamics, transport and their consequences in wetland ecosystems.