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Water Hyacinth Treatment Systems In Agricultural Watersheds

Permanent Link: http://ufdc.ufl.edu/UFE0024522/00001

Material Information

Title: Water Hyacinth Treatment Systems In Agricultural Watersheds Influence of Biomass Incorporation Into Soil on Phosphorus Retention
Physical Description: 1 online resource (110 p.)
Language: english
Creator: Catts, Cory
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

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

Notes

Abstract: High phosphorus (P) loads within agricultural runoff have been implicated in eutrophication of lakes and wetlands, such as the Everglades, throughout Florida. A key technology that holds considerable promise for controlling these loads in a cost-effective manner is the use of treatment wetlands. Water hyacinth (Eichornia crassipes) has been studied extensively and shown to be highly effective at removing P from agricultural runoff; however, the vegetation must periodically be harvested to maintain favorable plant growth. Widespread implementation of Eichornia crassipes treatment systems has been limited because specialized equipment is required for harvesting, and the value of the harvested plant biomass (e.g., as compost, or a feed ingredient) usually doesn?t cover the costs of harvesting and processing. This study implemented a novel approach for dealing with the harvested Eichornia crassipes biomass. Rather than periodically harvesting the biomass, the study investigates the utility of simply tilling the biomass directly into the soil when the standing crop becomes too dense. This could be a cost effective method of management that utilizes conventional farm machinery. Soils are the ultimate storage reservoir for P within treatment wetlands; this tilling approach may accelerate the rate of transferring organic matter and its associated P into permanent storage. In this study, through observation of water quality and soil properties, the effect tilling of Eichornia crassipes biomass has on treatment efficiency and soil P dynamics was investigated. A series of 24 mesocosms were closely monitored for a period of one year to evaluate changes in water chemistry and P pools within the soil. The mesocosms were periodically tilled and soil cores taken to evaluate the P storage pools in each mesocosm as a function of time. Phosphorus fractions within soil cores were identified using a phosphorus fractionation method. Over the one year period of the study, the vegetated treatments were able to reduce total phosphorus (TP) by an average of 64% with a maximum reduction of 72.5%. The vegetated treatments averaged an average mass reduction rate of 12.4 mg P m-2 day-1 with a maximum rate of 14.3 mg P m-2 day-1. The vegetated treatments provided significantly larger reductions in P than the unvegetated treatments, but within the vegetated treatments there were no significant differences. During the duration of the study soil organic matter increased in the treatments receiving biomass tilling by 1.8 and 1.2%, respectively, for the surface and subsurface soil treatments. There was a small increase in P stored in non-labile forms of P within the soil from 86.5% to 87.9%. The largest increase in a P fraction within the soils during the study was a 5.7% increase in residual organic P. The results of this study suggest that tilling water hyacinth biomass may be an effective management strategy for Eichornia crassipes treatment systems.
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 Cory Catts.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Reddy, Konda R.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024522:00001

Permanent Link: http://ufdc.ufl.edu/UFE0024522/00001

Material Information

Title: Water Hyacinth Treatment Systems In Agricultural Watersheds Influence of Biomass Incorporation Into Soil on Phosphorus Retention
Physical Description: 1 online resource (110 p.)
Language: english
Creator: Catts, Cory
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

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

Notes

Abstract: High phosphorus (P) loads within agricultural runoff have been implicated in eutrophication of lakes and wetlands, such as the Everglades, throughout Florida. A key technology that holds considerable promise for controlling these loads in a cost-effective manner is the use of treatment wetlands. Water hyacinth (Eichornia crassipes) has been studied extensively and shown to be highly effective at removing P from agricultural runoff; however, the vegetation must periodically be harvested to maintain favorable plant growth. Widespread implementation of Eichornia crassipes treatment systems has been limited because specialized equipment is required for harvesting, and the value of the harvested plant biomass (e.g., as compost, or a feed ingredient) usually doesn?t cover the costs of harvesting and processing. This study implemented a novel approach for dealing with the harvested Eichornia crassipes biomass. Rather than periodically harvesting the biomass, the study investigates the utility of simply tilling the biomass directly into the soil when the standing crop becomes too dense. This could be a cost effective method of management that utilizes conventional farm machinery. Soils are the ultimate storage reservoir for P within treatment wetlands; this tilling approach may accelerate the rate of transferring organic matter and its associated P into permanent storage. In this study, through observation of water quality and soil properties, the effect tilling of Eichornia crassipes biomass has on treatment efficiency and soil P dynamics was investigated. A series of 24 mesocosms were closely monitored for a period of one year to evaluate changes in water chemistry and P pools within the soil. The mesocosms were periodically tilled and soil cores taken to evaluate the P storage pools in each mesocosm as a function of time. Phosphorus fractions within soil cores were identified using a phosphorus fractionation method. Over the one year period of the study, the vegetated treatments were able to reduce total phosphorus (TP) by an average of 64% with a maximum reduction of 72.5%. The vegetated treatments averaged an average mass reduction rate of 12.4 mg P m-2 day-1 with a maximum rate of 14.3 mg P m-2 day-1. The vegetated treatments provided significantly larger reductions in P than the unvegetated treatments, but within the vegetated treatments there were no significant differences. During the duration of the study soil organic matter increased in the treatments receiving biomass tilling by 1.8 and 1.2%, respectively, for the surface and subsurface soil treatments. There was a small increase in P stored in non-labile forms of P within the soil from 86.5% to 87.9%. The largest increase in a P fraction within the soils during the study was a 5.7% increase in residual organic P. The results of this study suggest that tilling water hyacinth biomass may be an effective management strategy for Eichornia crassipes treatment systems.
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 Cory Catts.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Reddy, Konda R.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024522:00001


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1 WATER HYACINTH TREATMENT SYSTEMS IN AGRICULTURAL WATERSHEDS: INFLUENCE OF BIOMASS INCORPORATION INTO SOIL ON PHOSPHORUS RETENTION By CORY W. CATTS A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2009

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2 2009 Cory W. Catts

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3 ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Reddy, for his advice and support. I also thank my committee, Ed Dunne, Tom DeBusk, and Patrick Inglett, who contributed to the project. A special thanks to Ed Dunne for his extremely helpful input and advice in the pr ocess of writing. Without help from the staff at DB Environmental Laboratories, Inc. the logistics of the project would have been extremely difficult. Experiments described herein were based on and used with permission the patented technology and methods o f Thomas DeBusk, US Patent No. 7,074,330B1. Yu Wang, Gavin Wilson, and the rest of the Wetlands Biogeochemisty Lab staff were an enormous help in the lab. Funding was provided through the Florida Department of Agriculture and Consumer Services. I would lik e to thank Kristen Blanton for her support, advice, and friendship throughout the entire thesis process. Finally, I thank my family and friends for their endless love and support.

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4 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ ............... 3 LIST OF TABLES ................................ ................................ ................................ ........................... 6 LIST OF FIGURES ................................ ................................ ................................ ......................... 7 ABSTRACT ................................ ................................ ................................ ................................ ... 10 1 INTRODUCTION ................................ ................................ ................................ ...................... 12 Phosphorus Dynamics in Treatment Wetlands ................................ ................................ ....... 13 Wetland Phosphorus Cycle ................................ ................................ .............................. 14 Physical phosphorus retention processes ................................ ................................ 14 Chemical phosphorus retention processes ................................ ................................ 16 Biological phosphorus retention processes ................................ .............................. 17 Limitations of Treatment Wetland on Long Term Storage ................................ ............. 18 Management Strategies to Maximize Phosphorus Retention ................................ .......... 20 Water Hyacinth Treatment Systems ................................ ................................ ....................... 22 Research Objectives ................................ ................................ ................................ ................ 27 2 MATERIALS AND METHODS ................................ ................................ ................................ 30 Site Description ................................ ................................ ................................ ...................... 30 Sampling Methods ................................ ................................ ................................ .................. 31 Water Sampling ................................ ................................ ................................ ............... 31 Soil Sampling ................................ ................................ ................................ .................. 32 Vegetation Sampling ................................ ................................ ................................ ....... 32 Physical and Chemical Analysis ................................ ................................ ............................. 33 Water ................................ ................................ ................................ ............................... 33 Soil ................................ ................................ ................................ ................................ ... 33 Water content ................................ ................................ ................................ ........... 33 Bulk density ................................ ................................ ................................ .............. 33 pH ................................ ................................ ................................ ............................. 34 Total phosphorus ................................ ................................ ................................ ...... 34 Organic matter content ................................ ................................ ............................. 34 Soil phosphorus fractionation ................................ ................................ ................... 34 Vegetation ................................ ................................ ................................ ........................ 36 Statistical Analysis ................................ ................................ ................................ .................. 36 3 RESULTS AND DISCUSSION ................................ ................................ ................................ 42 Water Chemistry ................................ ................................ ................................ ..................... 42 Inflow Outflow N utrient Concentrations ................................ ................................ ........ 42 Phosphorus ................................ ................................ ................................ ............... 42

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5 Nitrogen ................................ ................................ ................................ .................... 45 Mass Removal ................................ ................................ ................................ ................. 46 Phosphorus ................................ ................................ ................................ ............... 46 Nitrogen ................................ ................................ ................................ .................... 47 Water Chemistry Discussion ................................ ................................ ........................... 48 Soil ................................ ................................ ................................ ................................ .......... 52 Physico chemical Soil Properties ................................ ................................ .................... 53 Bulk density ................................ ................................ ................................ .............. 53 pH ................................ ................................ ................................ ............................. 54 Soil organic matter ................................ ................................ ................................ ... 54 Phosphorus Forms ................................ ................................ ................................ ........... 56 Phosphorus Storage ................................ ................................ ................................ ......... 59 Soil Chemistry Summary ................................ ................................ ................................ 60 Phosphorus Budget ................................ ................................ ................................ ................. 60 4 SUMMARY AND CONCLUSIONS ................................ ................................ ....................... 104 LIST OF REFERENCES ................................ ................................ ................................ ............. 107 BIOGRAPHICAL SKETCH ................................ ................................ ................................ ....... 110

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6 LIST OF TABLES Table page 2 1 Inflow Water Summary ................................ ................................ ................................ ...... 37 2 2 Initial Soils Summary ................................ ................................ ................................ ........ 38 3 1 Inflow and outflow water quality data for TP, SRP, DOP, and PP with percent reduction ................................ ................................ ................................ ............................ 63 3 2 Inflow and outflow water quality data for TKN, NO 3 and NH 4 with percent reduction ................................ ................................ ................................ ............................ 64 3 3 Calculated mass removal (mg P m 2 day 1 ) for TP, SRP, DOP, and PP ............................ 65 3 4 Calculated mass removal (m g P m 2 day 1 ) for TKN, NO 3 and NH 4 ................................ 66 3 5 Summary of water hyacinth treatment systems performance in Florida with summary of study wetlands (data from Stewart et al. 1987). ................................ ............................ 67 3 6 Bulk density of soils throughout study period ................................ ................................ ... 68 3 7 pH of soils throughout study period ................................ ................................ .................. 69 3 8 Loss on ignition of soils throughout study period ................................ ............................. 70 3 9 Soil phosphorus fractionation data summary ................................ ................................ ..... 71 3 10 Total phosphorus of soils throughout study period ................................ ............................ 73 3 11 Phosphorus mass balance of system for duration of study ................................ ................ 74

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7 LIST OF FIGURES Figure page 1 1 Schematic of t he phosphorus cycle in wetlands ................................ ................................ 29 2 1 Diagram of mesocosm set up and design. Included are dimensions and volumes the different components. ................................ ................................ ................................ ........ 39 2 2 Mesocosm site layout with treatments and repetitions shown for both mineral and organic soils. ................................ ................................ ................................ ...................... 40 2 3 Diagram of the various treatments used during the study. ................................ ................. 41 3 1 Statistical ANOVA plot of TP mass reduction percent (%).. ................................ ............ 75 3 2 Statistical ANOVA plot of SRP mass reduction percent (%) ................................ ............ 76 3 3 Statistical ANOVA plot of DOP mass reduction percent (%) ................................ ........... 77 3 4 Statistical ANOVA plot o f PP mass reduction percent (%) ................................ .............. 78 3 5 Statistical ANOVA plot of TKN mass r eduction percent (%) ................................ ........... 79 3 6 Statistical ANOVA plot of NO 3 mass reduction percent (%) ................................ ............ 80 3 7 Statistical ANOVA plot of NH 4 mass reduction percent (%) ................................ ............ 81 3 8 Statistical ANOVA plot of TP mass removal (mg P m 2 day 1 ) ................................ ......... 82 3 9 Statistical ANOVA plot of SRP mass removal (mg P m 2 day 1 ) ................................ ...... 83 3 10 Statistical ANOVA plot of DOP mass removal (mg P m 2 day 1 ) ................................ ..... 84 3 11 Statistical ANOVA plot of PP mass removal (mg P m 2 day 1 ) ................................ ......... 85 3 12 Statistical ANOVA plot of TKN mass removal (mg P m 2 day 1 ) ................................ ..... 86 3 13 Statistical ANOVA plot of NO 3 mass removal (mg P m 2 day 1 ) ................................ ...... 87 3 14 Statistical ANOVA plot of NH 4 mass removal (mg P m 2 day 1 ) ................................ ...... 88 3 15 TP water quality throughout study period ................................ ................................ ......... 89 3 16 SRP water quality throughout study period ................................ ................................ ....... 90 3 17 DOP water quality throughout study period ................................ ................................ ...... 91 3 18 PP water quality throughout study period ................................ ................................ .......... 92

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8 3 19 TKN water quality throughout study period ................................ ................................ ...... 93 3 20 NO 3 water quality throughout study period ................................ ................................ ....... 94 3 21 NH 4 water quality throughout study period ................................ ................................ ....... 95 3 22 Initial and final no vegetation on surface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ ................. 96 3 23 Initial and final tilled on surface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ ......................... 96 3 24 Initial and final tilled with amendment on surface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ 97 3 25 Initial and final tiered tilled on surface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ ......................... 97 3 26 Initial and final no vegetation on subsurface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ ................. 98 3 27 Initial and final tilled on subsurface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ ......................... 98 3 28 Initial and final tilled with amendment on subsurface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ 99 3 29 Initial and final tiered tilled on subsurface soils phosphorus fractionation percent of total phosphorus ................................ ................................ ................................ ................. 99 3 30 Diagram of No Vegetation on Surface Soil (NVS) treatment mass balance and phosphorus distribution within the system for one year. ................................ ................. 100 3 31 Diagram of Tilled on Surfac e Soil (TS) treatment mass balance and phosphorus distribution within the system for one year. ................................ ................................ ..... 100 3 32 Diagram of Tiered Tilled on Surface Soil (TTS) treatment mass balance and phosphorus distribution within the system for one year. ................................ ................. 101 3 33 Diagram of Tilled w ith Amendment on Surface Soil (TAS) treatment mass balance and phosphorus distribution within the system for one year. ................................ .......... 101 3 34 Diagram of No Vegetation on Subsurface Soil (NVSS) treatment mass balance and phosphorus distribution within the system for one year. ................................ ................. 102 3 35 Diagram of Tilled on Subsurface Soil (TSS) treatment mass balance and phosphorus distribution within the system for one year. ................................ ................................ ..... 102

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9 3 36 Diagram of Tiered Tilled on Subsurface Soil (TTSS) treatment mass balance and phosphorus distribution within the system for one year. ................................ ................. 103 3 37 Diagram of Tilled with Amendment on Subsurface Soil (TASS) treatment mass balance and phosphorus distribution within the system for one year. ............................. 103

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10 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science WATER HYACINTH TREATMENT SYSTEMS IN AGRICULTURAL WATERSHEDS: INFLUENCE OF BIOMASS INCORPORATION INTO SOIL ON PHOSPHORUS RETENTION By Cory W. Catts May 2009 Chair: K. R. Reddy Major: Soil and Water Science High phosphorus (P) loads within agricultural runoff ha v e been implicated in eutrophication of la kes and wetlands, such as the Everglades, throughout Florida. A key technology that holds considerable promise for controlling these loads in a cost effecti v e manner is the use of treatment wetlands. Water hyacinth ( Eichornia crassipes ) has been studied ex tensively and shown to be highly effective at removing P from agricultural runoff ; however, the vegetation must periodically be harvested to maintain favorable plant growth. Widespread implementation of Eichornia crassipes treatment systems has been limite d because specialized equipment is required for harvesting, and the value of the harvested plant biomass (e.g., as This study implemented a novel approach for deal ing with the harvested Eichornia crassipes biomass. Rather than periodically harvesting the biomass the study investigates the utility of simply tilling the biomass directly into the soil when the standing crop becomes too dense. This could be a cost effe ctive method of management that utilizes conventional farm machinery. Soils are the ultimate storage reservoir for P within treatment wetlands; this tilling approach may accelerate the rate of transferring organic matter and its associated P into permanent storage. In this study,

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11 through observation of water quality and soil properties, the effect tilling of Eichornia crassipes biomass has on treatment efficiency and soil P dynamics was investigated. A series of 24 mesocosms were closely monitored for a per iod of one year to evaluate changes in water chemistry and P pools within the soil. The mesocosms were periodically tilled and soil cores taken to evaluate the P storage pools in each mesocosm as a function of time Phosphorus fractions within soil cores w ere identified using a phosphorus fractionation method. Over the one year period of the study, the vegetated treatments were able to reduce total phosphorus (TP) by an average of 64% with a maximum reduction of 72.5%. The vegetated treatments averaged an a verage mass reduction rate of 12.4 mg P m 2 day 1 with a maximum rate of 14.3 mg P m 2 day 1 The vegetated treatments provided significantly larger reductions in P than the unvegetated treatments, but within the vegetated treatments there were no signific ant differences. During the duration of the study soil organic matter increased in the treatments receiving biomass tilling by 1.8 and 1.2%, respectively, for the surface and subsurface soil treatments. There was a small increase in P stored in non labile forms of P within the soil from 86.5% to 87.9%. The largest increase in a P fraction within the soils during the study was a 5.7% increase in residual organic P. The results of this study suggest that tilling water hyacinth biomass may be an effective mana gement strategy for Eichornia crassipes treatment systems.

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12 CHAPTER 1 INTRODUCTION Nonpoint phosphorus inputs to downstream systems are a major cause of eutrophication within many watersheds. Use of treatment wetlands for reduction of phosphorus loads from agricultural runoff is often considered as a low cost alternative. A potential res traint on using wetlands as a treatment system is the efficiency and long term sustainability of the system to store phosphorus. The efficiency of a system to store phosphorus permanently is determined by the proportion of phosphorus stored in non labile f orms, such as residual organic phosphorus in the soil. A thorough understanding of the most efficient pathways and processes to move phosphorus from the water column to permanent storage in the soil is essential. One novel approach to maximizing this funct ion is a proposed management strategy which buries floating macrophytes in the soil through periodic mechanical tilling (DeBusk, 2005). This process may encourage the accumulation of organic matter and its associated phosphorus in long term storage. Float ing macrophytes such as water hyacinth ( Eichornia crassipes ) have been used to effectively treat wastewater in treatment systems. Water hyacinth have been found to reduce phosphorus levels in treatment systems by as much as 93% (Reddy and DeBusk, 1985). Ph osphorus uptake rates for water hyacinth have been estimated to be as high as 243 mg m 2 day 1 (Reddy and DeBusk, 1985). This high treatment efficiency can be attributed to the extraordinarily rapid growth rates of water hyacinth. Water hyacinth has been f ound to have maximum biomass yields of 64.4 g m 2 day 1 with an average long term yield of 27.1 g m 2 day 1 (Reddy and DeBusk, 1984). Other studies have found similar production rates of 29 g m 2 day 1 (Wooten and Dodd, 1976). With this rapid biomass produ ction, harvesting and disposal of these aquatic macrophytes can become problematic and costly. Several uses of excess biomass have

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13 been proposed, such as the production of gaseous fuels, livestock feed, fiber, and composting; however, transportation of the biomass may at times become too costly for efficient disposal. Mechanically tilling excess biomass into the soil may present a solution to this problem by disposing excess biomass on site while maintaining high treatment efficiencies in the system. The pu rpose of this study was to investigate the feasibility and functioning of tilling excess biomass into the onsite soils as a viable management strategy for maintenance of floating macrophyte treatment systems. A mesocosm study was designed to specifically i nvestigate how tilling practices influence treatment efficiency and soil phosphorus dynamics. This mesocosm study evaluated how organic matter accumulation rates were influenced, how soil phosphorus forms are changed as a function of time, and the stabilit y of these soil phosphorus pools. Phosphorus Dynamics in Treatment Wetlands Wetlands provide an essential function on the landscape, serving as a buffer between uplands and surrounding aquatic systems. One of the key roles wetlands perform on the landscap e is the ability to retain phosphorus within the wetland. This important function has implications on downstream water quality. As water moves across the landscape it transports phosphorus and other contaminants from uplands to aquatic systems. Wetlands re tain these contaminants within the system, having significant impacts on phosphorus loading to downstream aquatic systems (Reddy et al., 2005). Nonpoint phosphorus inputs to downstream systems is a major cause of eutrophication within many watersheds; thus an understanding and quantification of wetland phosphorus retention processes is key to utilizing wetlands for improved downstream ecosystem health (Richardson, 1999). From current understanding of wetland functions, the use of treatment wetlands to impr ove water quality has become a common practice.

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14 Wetland Phosphorus Cycle Phosphorus entering a wetland phosphorus cycle can be present in several different forms, and within the wetland can undergo transformations depending on its chemical, physical, and b iological environment Phosphorus within this cycle is present in organic and inorganic forms. These organic and inorganic forms are further grouped into dissolved organic phosphorus (DOP), particulate organic phosphorus (POP), dissolved inorganic phosphor us (DIP), and particulate inorganic phosphorus (PIP). DOP is commonly in the form of organic colloids, POP includes detrital phosphorus from vegetation and microorganisms, DIP is most common as orthophosphates, and PIP occurs as crystalline and amorphous p recipitates of phosphates and metal cations. DIP is bioavailable, while DOP, POP, and PIP must undergo transformations before they are bioavailable (Reddy et al., 2005) Figure 1 1 provides a graphical representation of the phosphorus cycle within a wetlan d, including many of the transformations. A key characteristic to note in the wetland phosphorus cycle is the ability to retain phosphorus within the system. Phosphorus retention is the ability of a wetland to remove phosphorus from the water column and s tore it in forms not readily released back to the water column through physical, chemical and biological processes ( Reddy et al., 2005, Richardson, 1999). Physical phosphorus retention processes One of the key physical phosphorus retention mechanisms is the process of phosphorus sorption on soils. Adsorption is the movement of soluble inorganic phosphorus from soil porewater to the soil surface. During adsorption, the phosphorus is accumulated on the surface of the soil particle. Desorption refers to the release of previously adsorbed phosphorus from the surface of the soil to the soil porewater (Reddy et al., 2005, Rhue and Harris, 1999). Phosphorus

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15 adsorption is mediated by two processes, ion exchange and ligand exchange (Rhue and Harris, 1999). The bala nce between adsorption and desorption creates an equilibrium between phosphorus in solid phase on soil surfaces and phosphorus in soluble phase in soil porewater. When soil particles become saturated with adsorbed phosphorus, the concentration of phosphoru s in the porewater is likewise high. If porewater phosphorus concentrations decrease, phosphorus will be desorbed into porewater to reach equilibrium once again. In a system at steady state, the phosphorus adsorbed maintains equilibrium with phosphorus in soil porewater. The reactions of adsorption and desorption are rapid and an equilibrium can be reached in a short time period (Reddy et al., 2005, Rhue and Harris, 1999). Although wetlands soils have an affinity for phosphorus, this retention process may not be a reliable long term removal mechanism. In most surface flow wetlands this storage compartment is quickly exhausted due to saturation and lack of binding sites. In most constructed treatment wetlands, the storage capacity of soil through adsorption is saturated within several years (Richardson and Craft, 1993). Another form of physical phosphorus retention within a wetland is sedimentation. As water enters a wetland the velocity of the water is reduced as a result of varied flowpaths and vegetation This reduction of velocity results in the settling of suspended particles that may contain phosphorus. Sedimentation includes several processes that influence phosphorus retention and accumulation. These processes are: the settling of inorganic suspended particles, the settling and adhesion of organic particles, and the accumulation of both autotrophic and heterotrophic materials. A significant amount of phosphorus may be removed from the water flowing through a wetland if velocity is slowed to the point where these particulate constituents

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16 and their attached phosphorus settle out of suspension. Sediment accumulation through sedimentation may provide long term storage of phosphorus in some systems (Reddy et al., 1999). Chemical phosphorus retention process es An additional important component assisting in wetland phosphorus retention is chemical retention. One of the dominant chemical removal mechanisms of phosphorus from the water column is co precipitation. Precipitation refers to the chemical reaction of phosphate anions and metallic cations in solution to form amorphous precipitate solids. Distinguishing between the contribution to phosphorus retention made by adsorption and precipitation can be difficult, because precipitation is often preceded by adsor ption to a soil surface (Rhue and Harris, 1999). Phosphate ions often form precipitate solids with cations, such as Fe, Al, Ca, or Mg, yet which cation a phosphate ion precipitates with is heavily influenced by the pH of the water column. In acidic environ ments phosphorus typically forms precipitate products with either Fe or Al, and in more alkaline systems phosphorus will commonly precipitate with Ca or Mg (Reddy et al., 2005). A precipitate reaction occurs when concentrations of phosphorus or metallic cations are elevated above a critical level. This critical level is reached when concentrations are high enough to surpass the concentration needed to form a seed crystal (Rhue and Harris, 1999). An example of a precipitation reaction that would occur in a lkaline conditions is as follows: Ca 2+ + HPO 4 2 4 [Precipitate] In alkaline environments, precipitation of phosphorus with Ca is very common. When phosphorus precipitates out of solution with Ca, the precipitation products form several types of phos phates. These phosphates include calcium phosphate, dicalcium phosphate, beta tricalcium phosphate, octacalcium phosphate, and hydroxyapatite. Hydroxyapatite is the most stable

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17 phosphate form within soils. Both dicalcium and octacalcium phosphate may trans form to the more stable hydroxyapatite over time, at continuous high phosphorus concentrations (House, 1986). Biological phosphorus retention processes Organisms within wetland systems have a significant impact on the ability of a wetland to retain phosphorus. All living organisms utilize phosphorus within their tissues. Within plants and microorganisms, phosphorus is a major constituent of macromolecules such as nucleic acids (DNA and RNA). Phosphorus is also present in phospholipids of membranes, m onoesters, and many other components of tissues. Within angiosperms, one of the major phosphorus containing compounds is hexaphosphate (IHP) (Reddy et al., 2005). Concentrations of phosphorus in tissue of water hyacinth range from 1.4 to 12.0 g P kg 1 on a dry weight basis (Reddy and DeBusk, 1987). Plants and microbiota are dependent on attaining DIP, the only bioavailable form of phosphorus, from the surrounding environment. Floating macrophytes are able to take phosphorus directly out of the water column but emergent macrophytes are depended on attaining phosphorus from soil pore water. Although emergent macrophytes do not remove phosphorus from the water column, they can promote the establishment of a gradient between the water column and soil, thus imp roving overall water quality (Reddy et al. 1999). Plants and microbiota within wetlands must be able to utilize phosphorus rapidly because it is typically a limiting nutrient. Plants generally have relatively rapid phosphorus uptake and incorporation rate s. Phosphorus uptake in plants occurs on the order of days to weeks. This uptake is extremely slow compared to the phosphorus uptake of microbiota. Microbiota have a much higher rate of uptake because they grow and multiply at higher rates then macrophytes Uptake can occur in microbiota in less then an hour (Kadlec and Knight, 1996).

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18 Macrophytes have the potential to store phosphorus within the structure of both its living and its dead tissues. The amount of phosphorus wetland vegetation can store is depe ndent on several factors, including type of vegetation, decomposition rates of litter, leaching rates of phosphorus from detrital tissue, C/P ratio of detrital tissue, and movement of phosphorus from above ground biomass to below ground biomass (Reddy et a l. 1999). Emergent macrophytes have an extensive system of below ground biomass comprised of a network of rhizomes and roots. These structures provide plants with the ability to store large amounts of phosphorus and account for a large portion of active ph osphorus storage (Reddy et al. 1999). Although macrophytes store large amounts of phosphorus, most of the stored phosphorus is only stored short term. The above ground biomass of most wetland vegetation grows and dies in cycles. In northern climates the c ycle is on an annual period. But in warmer southern climates biomass turnover may be 2 or 3 times a year. In eutrophic systems up to 80% of the phosphorus stored in living tissue is released during decomposition. The above ground biomass of macrophytes and microbiota releases phosphorus to the water column and deposits residual detrital materials to the soil surface. The below ground biomass of macrophytes adds phosphorus to the soil pore water, and residual detrital materials to the subsurface soils. This residual detrital material deposited by both plants and microbiota is incorporated as newly accreted soil. Although this amount of residual detrital material is only a small fraction of the original biomass, it has a large impact on long term phosphorus st orage. The burial and accretion of this residual biomass and the phosphorus it contains is the only reliable and sustainable long term storage mechanism of phosphorus in wetland systems (Reddy et al. 1999). Limitations of Treatment Wetland on Long Term Sto rage Phosphorus retention in wetlands is dependent on several compartments for storage. These storage compartments can be classified as either short term or long term storage units.

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19 Short term storage compartments include algae, microbes, plants, and loos ely bound adsorbed phosphorus on soil particles. The only long term storage unit is burial in the soil. Each of the short term storage units is limited in the amount and rate of phosphorus uptake. Once a storage compartment is full it can store no more and will not function in phosphorus removal and storage. Once saturated, the short term storage compartments will have little or no effect on reducing phosphorus water concentrations. The only way to maintain long term phosphorus uptake is to balance input le vels of phosphorus with long term uptake rates. Once the short term storage compartments are saturated, the long term phosphorus uptake is dependent on the peat or soil accretion rate of the wetland (Richardson and Craft, 1993). The peat or soil accretion rates within freshwater wetlands can often be extremely slow. This factor may significantly hinder the ability of treatment wetlands to retain large amounts of phosphorus on a long term basis. Based on several studies of the soil accretion rates of wetla nds, correlated with phosphorus storage in newly accreted soil, it appears wetlands have a limited ability to permanently store phosphorus. The studies suggest permanent phosphorus storage in wetlands may be around 0.5 g m 2 year 1 (Richardson and Craft, 1 993; Nichols, 1983). Low rates of long term storage suggest water may not be effectively treated using treatment wetlands after several years of use, once short term storage is saturated, without using vast amounts of land to compensate for slow areal upt ake rates. Based on a study by Richardson and Craft (1993), the amount of land that would be needed to effectively treat large amounts of highly phosphorus enriched water would be excessively large. Based on a 0.4 g m 2 year 1 retention value it would take around 1000 ha (2471 acres) to store 4.0 tons of phosphorus permanently.

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20 The limitations associated with the long term use of treatment wetlands affect the viability of treatment wetlands to store phosphorus efficiently once the short term storages are s aturated. Without further management, treatment wetlands may have an effective treatment life span followed by a much slower long term uptake phase. To effectively remove phosphorus from wastewater using treatment wetlands on a long term scale, different i nnovative management strategies must be implemented to supplement the smaller amounts of phosphorus removed by the long term storage compartment. Management Strategies to Maximize Phosphorus Retention There are several management practices that may be us ed to enhance the natural ability of wetlands to retain phosphorus. These methods may aid in supplementing the slow long term storage rates aging treatment wetlands often experience. One of these management strategies is vegetation harvesting. Vegetation m anagement is a process where either macrophytes or algae, and their associated sequestered phosphorus, are removed from the system. The second management strategy is the use of chemical amendments to enhance phosphorus adsorption. Although these management practices look promising, they have not received widespread acceptance from practitioners, as these management regimes contradict the idea of treatment ability t o store phosphorus on a long term basis, these practices should continue to be researched, and in some cases applied (DeBusk and Dierberg, 1999). Vegetation harvesting may prove to be a viable means of increasing phosphorus removal rates by treatment wetl ands. Vegetation has an increased productivity with rapid phosphorus uptake rates when introduced to highly nutrient enriched water. If the vegetation in treatment wetlands was periodically removed, a significant amount of phosphorus held in the biomass co uld be removed from the system (DeBusk and Dierberg, 1999).

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21 Several types of vegetation could be harvested to increase phosphorus removal rates. Floating macrophytes, emergent macrophytes, submerged macrophytes, and periphyton are all potential harvestable biomass. Floating macrophytes and periphyton offer the greatest promise as harvestable vegetation to improve treatment wetland performance. Floating macrophytes and periphyton offer promise because they rapidly and directly remove phosphorus from the wate r, and their biomass is easily harvested. Vegetation harvesting can provide a substantial increase in phosphorus removal (DeBusk and Dierberg, 1999). There are several chemical amendment methods that may be used to increase phosphorus retention in treatme nt wetlands. The use of chemical phosphorus adsorbing amendments in wetlands refers to adding a variety of chemicals either to inflow water or to the soil of the wetland, to increase the amount of phosphorus removed from the water. Some of the chemicals us ed are FeCl 3 (ferric chloride), Al 2 (SO 4 ) 3 (alum), Ca(OH) 2 (lime), and CaCO 3 (calcium carbonate). The use of these chemicals is based on the affinity for phosphorus to adsorb to either Fe or Al in acidic systems, and Ca in alkaline systems (DeBusk and Dierberg, 1999). One method for utilizing this chemically enhanced adsorption i s the use of coagulation agents in inflow water. A chemical inflow treatment system would add a continuous flow of a coagulant, such as alum, into the inflow water. The phosphorus would then bind to the coagulant and flocculation would occur. After floccul ation the phosphorus would settle out of suspension and would soon be buried in the soil for long term storage. For this type of system, alum and ferric chloride have proven effective. Another method using chemical amendments is mixing chemically active ph osphorus adsorbing compounds directly into the soil. This method would management strategy would involve mixing either alum or ferric chloride with the wetlan d soil

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22 either before flooding or during drawdown periods. By enhancing the ability of soils to adsorb phosphorus, the efficiency of the wetland to retain phosphorus is greatly improved (DeBusk and Dierberg, 1999). With these management practices, the life span and efficiency of treatment wetlands may be improved. Although the use of treatment wetlands is continually evolving, it has advanced rapidly in recent years. With continued research and application, treatment wetland function and efficiency will cont inue to increase. With improved function through design and research, treatment wetland application may become more widespread and assist in minimizing impacts on our surrounding environment. Water Hyacinth Treatment Systems Interest in macrophyte based t reatment systems has increasingly been considered for treatment of phosphorus in waste waters due to of several important factors. The first of these factors is that there are no cost effective conventional treatment technologies that can achieve very low phosphorus values in outflow waters. In many situations, the cost of treating wastewater can be reduced significantly by implementing an aquatic macrophyte based system, rather than expensive conventional treatment methods (Duffer, 1982). Second, these mac rophytes based systems can accommodate water storage in the systems, which makes them ideal for the variable inflow rates often associated with runoff sources like agricultural wastewaters. The third factor encouraging the development of macrophyte based t reatment systems is the availability of land needed for the land intensive macrophyte based systems, such as agricultural areas of Florida. (DeBusk et al. 2001). Of the many possible vegetation types that can be used in macrophyte treatment wetland syste ms, water hyacinth has been investigated and suggested to be one of the viable options for effective reduction of phosphorus in waste waters. The use of floating macrophytes, such as

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23 water hyacinth, for wastewater treatment is appealing for several reason s, including the extremely high productivity of water hyacinth, the practicality of stocking and harvesting of biomass in the system, and the high nutrient content of water hyacinth relative to other emergent macrophyte species (DeBusk and Reddy, 1987). Ma ny studies found water hyacinth to be the most productive aquatic plant species under ideal conditions, with biomass production rates of 42 g dry wt. m 2 and P assimilation rates of 135 g P m 2 yr 1 (Reddy et al. 1983; Reddy and DeBusk, 1985). Water hyacin th treatment systems are successful at significantly reducing both phosphorus and nitrogen in waste waters through several processes. Phosphorus can be removed from wastewater in water hyacinth treatment systems through microbial assimilation, adsorption t o organic matter and clays, precipitation with divalent and trivalent cations, and plant uptake and harvest. It has been reported that the most significant and only reliable long term phosphorus removal process in water hyacinth treatment system s is throug h plant uptake and harvest (DeBusk and Reddy, 1987). Nitrogen removal in water hyacinth treatment systems is facilitated by plant uptake, microbial immobilization, and nitrification denitrification reactions. It has been found that the dominant nitrogen s ink in water hyacinth treatment systems is through the nitrification denitrification pathway (Stowell et al. 1981; DeBusk et al. 1983). This nitrification denitrification process is facilitated by the interface of the oxidized root zone and anaerobic zones within the system. Ammonium within the system undergoes nitrification in the oxidized root zone of the water hyacinth. The nitrate N is formed through nitrification and then diffuses to anaerobic zones within the system, where it is utilized as an electro n acceptor for facultative anaerobic bacteria. This denitrification process, facilitated by anaerobic bacteria, converts

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24 nitrate N to nitrogen gas and is removed from the system (DeBusk and Reddy, 1987). Denitrification rates in floating aquatic macrophyte systems have been reported to have maximum removal rates ranging from 6 to 22 kg ha 1 d 1 (Stowell et al 1981; Reddy, 1983). Water hyacinth treatment systems have a proven track record of performance. Several water hyacinth treatment systems were construc ted throughout Florida in the early 1980s to treat domestic waste water ranging from 0.5 ha to 12.2 ha in size. The P mass removal rates of these systems ranged from 11.3 to 51.9 g P m 2 yr 1 Outflow concentrations as low as 0.1 mg P L 1 were achieved in one of these systems (DeBusk and Reddy, 1989; Stewart et al. 1987). Water hyacinth has been used for removal of phosphorus from eutrophic lake waters. Three 372 m 2 raceways were constructed and monitored for 18 months under different conditions. The first raceway contained water hyacinth which were periodically harvested, while the second was not harvested, and the third was a non macrophyte control. The harvested raceway provided phosphorus removal rates of 24.6 g P m 2 yr 1 the non harvested raceway achi eved removal rates of 22.2 g P m 2 yr 1 and the non macrophyte control had removal rates of 16.4 g P m 2 yr 1 It was found in this system that plant assimilation only accounted for 22% in the non harvested system and 40% in the harvested systems, so sedi mentation of particulate phosphorus was the primary phosphorous sink in this system, due to the high percentage of phosphorus in the inflow water as particulate phosphorus (Fisher and Reddy, 1987). Water hyacinth systems have been used to treat dairy lagoo n wastewater. In a dairy north of Lake Okeechobee, a mesocosm study was performed to evaluate the ability of water hyacinth to treat phosphorous from highly eutrophic dairy wastewater lagoons. The water hyacinth system was able to reduce phosphorus concent rations from 7.3 mg L 1 to 0.2 mg L 1 and removed phosphorus at a rate of 47 g P m 2 yr 1 (DeBusk et al. 1996).

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25 One major factor influencing the success of water hyacinth systems for reducing phosphorus is routine biomass harvesting. Productivity and phosphorus uptake rates are strongly dependant on the standing crop density. The highest productivity yields occur when plant density is maintained within a certain density range. For water hyacinth this range was found to be 0.5 2.0 kg m 2 (DeBusk et al. 1981; Reddy and DeBusk, 1984). In a small scale water hyacinth treatment system vegetation harvesting effects on phosphorus removal was investigated. The study compared similar harvested and non harvested ponds within the system. Phosphorus removal in the pond which received routine biomass harvesting averaged 29.9 g P m 2 yr 1 while the system without harvesting had a lower removal rate of 6.6 g P m 2 yr 1 (DeBusk et al. 1983). For this reason, a carefully planned and maintained harvesting schedule is impo rtant for water hyacinth treatment systems to be successful. During the late 1980s water hyacinth treatment systems became less desirable treatment technologies for several reasons. One of these was the susceptibility of large monocultures of water hyacin th to pest damage, which would significantly reduce treatment ability (Stewart et al. 1987). Another reason water hyacinth became less utilized was the cost restraints of harvesting, as specialized equipment was needed to harvest biomass, and there were no viable economic disposal methods or products of value (DeBusk et al. 2001). Capital and operating cost of water hyacinth treatment systems are reported to be lower then the cost of conventional treatment systems (Crites and Mingee, 1987). However, water hyacinth treatment systems can be land intensive, with 4 to 12 ha needed for each 3800 m 3 wastewater per day, and produce large amounts of harvested biomass. This large amount of biomass drives the development of efficient disposal or utilization methods (Reddy and Sutton, 1984). Water hyacinth treatment systems can produce very large amounts of biomass to be

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26 harvested and disposed. In a system under unoptimized conditions, biomass production was found to be 45 to 58 Mg ha 1 yr 1 In a system with a harves ting schedule providing the optimum plant density of 20 36 kg m 2, the biomass production was increased to 60 70 Mg ha 1 yr 1 (Hayes et al., 1987). This is a large amount of biomass that needs to be disposed of in an economically efficient manner. Within w ater hyacinth treatment systems, plant harvesting is the most expensive operational requirement (DeBusk et al., 1989). Cost of harvesting in a treatment system is influenced by methods and frequency of harvesting, disposal of biomass, and any economic bene fit from reuse of biomass, such as methane gas production. Smaller systems will not be suited for this last consideration in cost reduction, because the small scale system does not allow for efficient use of biomass for economic gain. (G. J. Thabaraj, 1987 ). For long term success of water hyacinth treatment systems, the cost of the three major components of the system must be as efficient as possible. These major components that must be efficient are: the system itself, the harvesting and handling of biomas s, and the biomass disposal (Hayes et al. 1987). Along with reducing the cost of water hyacinth treatment systems, tilling of biomass may help increase phosphorus retention by augmenting organic matter accumulation and associated phosphorus in the soils. As previously mentioned, peat or soil accretion is the only reliable long term phosphorus storage unit (Richardson and Craft, 1993). Wetland soils are characterized by slow decomposition of organic matter, due to flooded conditions and anaerobic zones with in the soil ( Fisher and Reddy, 2001 ). This slow decomposition of organic material within the anaerobic soil prevents the release of organic bound nutrients in buried biomass ( McLatchey and Reddy, 1998 ). The long term phosphorus storage in wetlands depends on this low rate of biomass, and is dependent on the incorporation of organic phosphorus into the soil system ( Richardson and

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27 Marshall, 1986 ). Therefore, incorporating harvested biomass directly into the soils should increase the organic matter content of the soil, and as a result increase the long term storage of phosphorus within the system. In order to encourage the economic viability of water hyacinth systems, it is the aim of this study to investigate the feasibility of streamlining the disposal of harvested biomass while improving phosphorus treatment and retention within the syste m. To streamline and reduce the cost of disposal of harvested biomass, this study will examine the utility of tilling harvested water hyacinth biomass onsite in the soils of the treatment system. This would reduce the cost of both the harvesting and dispos al of biomass, making water hyacinth treatment systems more economically feasible for widespread application, while improving phosphorus storage and retention. Research Objectives The overall objective of this study was to determine the feasibility of veg etation incorporation into the soil as a management tool, to increase phosphorus retention and reduce the cost of floating macrophyte treatment systems. Specific objectives of this study were to: Monitor and determine how concentrations of TP, SRP, DOP, a nd PP are reduced in the various tilling methods in the water hyacinth treatment systems in this study. It was expected to see significant reductions of total phosphorus in the vegetated mesocosms, with SRP being the majority of total phosphorus removed. S maller reductions of both DOP and PP were expected in the system. Monitor and determine the efficiency of these tilled water hyacinth treatment systems at reducing nitrogen concentrations in the forms of TKN, NO 3 and NH 4. Nitrogen was expected to be reduc ed significantly in treatments with vegetation. The majority of nitrogen removed from the system was expected to be removed through the denitrification of NO 3 An unvegetated treatment will serve to distinguish the influence water hyacinths have on reducti on of phosphorus and nitrogen within the system, and determine the extent of the treatment provided by the soils receiving tilling. It was expected the unvegetated treatments would have much lower treatment efficiency and a negligible increase in organic m atter without biomass tilling.

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28 Determine the treatment efficiency of a water hyacinth treatment system under a biomass tilling regime, and how this tilling of biomass into the soils may influence soil organic matter content and the associated phosphorus. I t was expected tilling of biomass into the soils will increase soil organic matter and increase recalcitrant soil phosphorus fractions, such as residual phosphorus. Investigate how a tiered tilling method may assist in the additions of organic matter and r eduction of phosphorus and nitrogen, as the buried plant matter is left undisturbed for longer periods of time. This tilling method was expected to have more efficient reduction of phosphorus, as the potential phosphorus flux from the soil maybe reduced af ter each tilling due to the lower level of disturbance. Determine how a soil surface amendment of ferric chloride in a tilled system will effect the phosphorus concentration reduction during the study. It was expected that the surface amendment will reduce the amount of phosphorus flux leaving the soil after reflooding, while improving the soils adsorption capacity. The tilled with amendment treatment was predicted to have the highest level of phosphorus reduction of the various treatment types. Determine h ow soil organic matter content is influenced through repeated tilling of water hyacinth biomass. It was expected that an increase of soil organic matter will occur in treatments receiving biomass tilling, leading to an accumulation of phosphorus in long te rm storage within the system. Determine how soil phosphorus pools are influenced by the incorporation of plant biomass and chemical amendments within the mesocosms throughout the study period using a soil phosphorus fractionation. An increase in recalcitra nt forms of phosphorus, such as residual phosphorus, was expected in treatments receiving biomass incorporation. An increase in Fe bound phosphorus was also predicted in the treatments receiving the ferric chloride amendment.

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29 Figure 1 1. Schematic of t he phosphorus cycle in wetlands. DIP = dissolved inorganic phosphorus, DOP = dissolved organic phosphorus, PIP = particulate inorganic phosphorus, and POP = particulate organic phosphorus (Reddy et al. 2008).

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30 CHAPTER 2 MATERIALS AND METHODS Site Description The study was conducted in a series of mesocosms, located in Port Myacca, FL on the eastern shore of Lake Okeechobee. The mesocosm experiment was established in 24 mesocosm tanks measuring 170 cm tall with a diameter of 117 cm. The surface area of each mesocosm was 1.07 m 2 Soil in each mesocosm was approximately 83 cm deep with a water depth maintained at 70 cm (Figure 2 1). Water was continuously pumped from Lake Okeechobee into a head tank, which distributed water to the mesocosms in a gravit y fed flow through system (Figure 2 2). Water from Lake Okeechobee during the study period had an average total phosphorus (TP) 1 1 (Table 2 1). Water from Lake Okeechobee was applied to each mesoc osm at a 7 cm day 1 hydraulic loading rate, giving each mesocosm a retention time of 10 days. Soils used in the mesocosm study were obtained from a local soil mine, operated by Sheltra Construction Inc. in Indiantown, FL. The area where the soils were min ed is listed to be the soil series Floridana fine sand, depressional. The Floridana series are loamy, siliceous, hypothermic Arenic Argiaquolls. The Floridana fine sand, depressional series has a sandy surface with slightly elevated organic matter content and a subsurface of fine sandy loam. The two soils used in this study were a surface soil which consisted of the A horizon and a subsurface the subsurface soil had higher Ca and Mg concentrations then the surface soil, while the surface soil had higher Fe and Al concentrations (Table 2 2). A single point isotherm was performed to determine the phosphorus sorption maximum of each soil. The single point isotherm indicated that the surface

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31 soil had a slightly higher sorption capacity of 300 mg kg 1 while the subsurface soil had a sorption capacity of 220 mg kg 1 (Table 2 2). Meso cosms with vegetation were initially started with 1.5 kg of water hyacinth and allowed to grow until maximum coverage was achieved. Once maximum coverage was present the mesocosms were drained to the surface of the soil and tilled. Tilling was conducted us ing a differed in application and methods (Figure 2 3). The experiment included four treatments for each soil, surface soil and subsurface soil. Each treatment had three replicates. The four treatments were as follow: Tilling tilling of biomass throughout the depth of the soil profile. Tilling with chemical amendment tilling of biomass throughout the depth of the soil profile with the addition of a ferric chlori de chemical amendment. Ferric chloride was applied to the surface of the soil after tilling events to reduce phosphorus flux from the soil upon reflooding. Tiered Tilling tilling of biomass into soil at incremental depths, starting at 40 cm deep and movi ng up 10 cm with each sequential tilling event. This tilling treatment was intended to represent a specialized tilling method which can till to a specific desired depth that allows for layering of tilled biomass. Tilling with No Vegetation this treatment did not have water hyacinth present. The soil profile was still tilled through the depth of the soil profile but in the absence of vegetation. This treatment was a control treatment free of vegetation but was also tilled, to isolate water treatment due to soil adsorption and other soil processes. Sampling Methods Water Sampling Water samples were collected from the inflow and outflow water of each mesocosm biweekly for a period of one year (April 25 th 2007 to April 15 th 2008). Water samples were collected in pre labeled 20 ml vials for water quality analysis. Water samples were analyzed for total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP),

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32 NO 3 total Kjeldahl nitrogen (TKN), NH 4 + pH, and water temperature. Samples for TKN and TP were collected and acidified with concentrated H 2 SO 4 to a pH less than 2 (1 drop per 20 mls) and preserved on ice until returned from the field A disposable, inline 0.45 micron filter was used to filter water for TDP, NH 4 + NO 3 and SRP. The TDP samples were acidified similar to those for TP and TKN, and the remaining sample bottles were capped and placed on ice without acidification until returning from the field. The NO 3 TKN, and NH 4 + parameters were m easured in water samples collected less frequently, such as during every other sampling period. Soil Sampling Soil cores were collected from each mesocosm before each of the three tilling events (5/30/07, 9/20/07, and 2/6/08). Soil samples were obtained us ing a 10 cm diameter aluminum coring tube. Cores were taken to a depth of 50 cm. Soil samples were extruded into large zip lock plastic bags and preserved on ice for transport back to the laboratory. Soil samples were then weighed, homogenized, and transfe rred to air tight polyethylene containers to be stored at Vegetation Sampling Water hyacinth plants were removed from each mesocosm and allowed to drip drain for five minutes prior to weighing. Total plant weights were obtained. A portion of water hyacinth weighing 1.5 kg was set aside for restocking each mesocosm for continued growth. A subsample was also set aside and placed in a paper bag for drying. Water hyacinth samples and bag s were weighed and placed in a drying room at 70C for 48 hours until fully dry. Water hyacinth and bags were once again weighed for dry weights. Plant biomass was then brought to the lab for further analysis.

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33 Physical and Chemical Analysis Water Water sam ples including TP, TDP, and SRP were held in a refrigerator at 4 o C until analysis. Analysis of all samples occurred within 30 days of collection. TP, TDP, and SRP were determined by the automated ascorbic acid reduction method (Standard Methods 18th ed, 45 00 PF). TKN was measured using the total Kjeldahl nitrogen digestion method, EPA Method 351.2 (EPA, 1979). NO 3 was measured using EPA method 353.2 (EPA, 1979), and NH4 analysis utilized the EPA method 350.1 (EPA, 1979). Soil Physicochemical soil properties including water content, bulk density, pH, and organic matter content were determined. The soils were also fractionated for labile and stable P pools using an inorganic P fractionation. Total phosphorus was measured separately using the ash TP procedure. Water content Percent moisture was determined by drying soil in a drying oven. The wet soil was weighed in an aluminum weigh dish and dried in an oven at 70 o C until a constant weight was obtained. The dry weights were recorded. Percent moisture was calculated by determining the ratio between the weight of dry soil and the weight of wet soil. Bulk density The mass of dry soil was determined by back calculati ng from the total wet weight using the percent moisture of the sample. The bulk density (g cm 3 ) was then calculated by dividing the mass of dry soil (g) by the total volume of the soil core (cm 3 ).

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34 pH The pH of the sample soil was determined using a 1:1 s oil:water slurry using distilled, deionized water. The slurry was then measured for pH using a pH meter after equilibrating. Total phosphorus Total phosphorus was measured by combusting dry soil samples in a muffle furnace at 550C for 4 hours. The remain ing ash was digested with 6 M HCl (Anderson, 1976). The digested solution was then analyzed for TP using EPA Method 365.1 (EPA, 1983). Organic matter content Total organic matter content was determined by mass loss on ignition (LOI), as an intermediate st ep in the TP ashing procedure. Dry soil samples were weighed before being combusted in the muffle furnace and then weighed after combustion. The difference was noted as the mass of organic matter (American Public Health Association, 1992). Soil phosphorus fractionation An inorganic phosphorus fractionation was used to determine the labile and stable phosphorus pools in each sample. Each soil sample was analyzed using inorganic sequential chemical extraction to provide the following phosphorus soil fractions : loosely bound or labile phosphorus, Fe/Al bound phosphorus, Ca/Mg bound phosphorus, and residual or recalcitrant organic phosphorus. The fractionation scheme to be used was a modification of a fractionation scheme developed by Chang and Jackson (1957). T his fractionation scheme has been used successfully to classify phosphorus forms in wetland soils (Reddy et al. 1998). The extraction was conducted with a 1:50 soil:solution (weight to volume) ratio using field moist samples, with the ratio calculated on s oil dry weight basis. Po tassium chloride extractable p hosphorus (Labile phosphorus) : In this first step of the fractionation scheme the readily available pool of phosphorus was determined by extracting

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35 field wet soil with a 1 M KCl solution. The soil susp ension was equilibrated for 2 hours by continuous shaking on a mechanical shaker. The soil suspension was then centrifuged at 6000 rpm for 10 minutes. The supernatant solution was then filtered through a 0.45 m membrane filter. Soluble reactive phosphorus (SRP) was then measured in the solution (U.S. Environmental Protection Agency, 1983, Method 365.1). The residual soil sample after this extraction was used for the next extraction in the series. Sodium h ydroxide extractable p osphorus (Al/Fe bound phosphor us and hydrolysable organic phosphorus) : The residual soil was then treated with 0.1 M NaOH for 17 hours on a mechanical shaker. The soil suspension was centrifuged and filtered as describe above. The supernatant was then split. Some of the NaOH extract un derwent digestion with 6 M HCl at 550 for 6 hours to determine TP in the extract. The other portion of the NaOH extract was acidified and centrifuged, and then measured for SRP (U.S. Environmental Protection Agency, 1983, Method 365.1). The measurement of SRP represented the Fe/Al bound phosphorus fraction in the soil. The difference between SRP and TP represents hydrolysable P o or fulvic and humic bound phosphorus fraction in the soil. Hydroc hloric acid extractable p hosphorus (Ca/Mg bound phosphorus) : Residual soil from the above extraction was then treated using 0.5 M HCl with a 24 hour equilibrium period on a mechanical shaker. The soil suspension was then centrifuged and filtered as described above. The filtrate was analyzed for SRP using EPA Method 365.1. The HCl extractable phosphorus represents the Ca/Mg bound phosphorus fraction within the soil sample. Residual p hosphorus : The remaining residual soil from the above extractions was then in 6 M HCl and analyzed using

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36 EPA Method 365.1. This process provides the amount of residual phosphorus present in the soil sample. Vegetation Water hyacinth samples were weighed, dried at 70C for 48 hours, and then weighted again. Dried vegetation samp les were combusted in a muffle furnace. Ash total phosphorus digestion was used to determine total phosphorus content of the vegetation. The digestion solution was then analyzed for TP using EPA Method 365.1 (EPA, 1983). Statistical Analysis In order to de termine significant differences between various measured values among the different treatment types applied in this study, a one way ANOVA was performed. The one way ANOVA was conducted using the software package JMP 7 by SAS.

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37 Table 2 1. Inflow Water Summary Mean S.D. Max. Min. 234.0 100.3 502.0 131.0 146.0 96.0 362.0 56.0 DOP 47.5 22.8 87.0 12.0 55.1 26.1 130.5 24.0 TKN 2.1 0.4 2.9 1.6 NO 3 0.3 0.1 0.2 0.4 NH 4 0.1 0.1 0.3 0.0 pH 7.7 0.2 8.2 7.3 Temp. (C) 29.0 4.3 34.7 17.2 Period record: 5/16/07 2/25/08 TP = Total Phosphorus SRP = Soluble Reactive Phosphorus DOP = Dissolved Organic Phosphrous PP = Particulate Phosphorus TKN = Total Kjeldahl Nitrogen

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38 Table 2 2. Initial Soils Summary Surface Soil Subsurface Soil Units Mean S.D. Mean S.D. Organic Matter % 6.1 0.5 4.2 0.8 pH 7.4 0.1 7.6 0.2 Bulk Density (g/cm3) 1.1 0.1 1.2 0.1 Ca (mg/kg) 7681 601 10146 97 Mg (mg/kg) 215 17 289 8 Fe (mg/kg) 570 59 476 23 Al (mg/kg) 746 60 564 14 P sorption maximum* (mg/kg) 305 55 220 97 *Estimated using single point isotherm

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39 Figure 2 1. Diagram of mesocosm set up and design. Included are dimensions and volumes the different components.

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40 Figure 2 2. Mesocosm site layout with treatments and repetitions shown for both mineral and organic soils.

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41 Figure 2 3. Diagram of the various treatments used during the study. The treatments include tilling with vegetation, tilling with vegetation and ferric chloride amendment, tiered tilling with vegetation, and tilling without vegetation.

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42 CHAPTER 3 RESULTS AND DISCUSSI ON Water Chemistry Water quality was closely monitored and evaluated to help determine the utility of tilling water hyacinth biomass into soil of treatment wetlands. A routine monitoring program was established, to ensure that treatment systems which receive tilling of water hyacinth biomass into ons ite soils are successful in water quality improvement. Water quality was regularly collected from inflow and outflow waters, to evaluate the treatment efficiency and removal rates for various phosphorus and nitrogen parameters. These values were used to as sess the water quality improvement achieved for each of the various mesocosm treatments applied in the study. The values varied over the study period in response to changes in inflow water concentrations and changes in water hyacinth density. For a summary average values across the study period were used, but maximum and minimum values were given to represent the variability throughout the study period. Inflow Outflow Nutrient Concentrations Phosphorus Inflow water from Lake Okeechobee during the study pe riod had an average TP 1 1 Soluble reactive phosphorus 1 1 During the study period DOP was 20% of the TP entering the 1 1 Particulate phosphorus 1 and a range of 26 to 1 (Table 2 1).

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43 To tal phosphorus was used to evaluate the overall treatment efficiency of each treatment in reducing phosphorus. Every treatment was successful in reducing TP concentrations in the inflow water. The TP reduction percentage for all treatments ranged from 19% to 68% (Table 3 1). Although all treatments reduced TP to some degree, the two treatments void of vegetation had the lowest percent reduction, with 19% and 30% for subsurface soil and surface soil, respectively (Table 3 1). These two treatments were signif icantly different (p<0.05) than the treatments with vegetation (Figure 3 1). This was expected, as treatments void of vegetation were lacking the nutrient uptake capabilities of the water hyacinth. The TP reductions observed in the no vegetation treatments were most likely due to sedimentation, uptake by algae in the water column, and adsorption by the soils. The vegetated treatments which were either tilled, tiered tilled, or tilled with chemical amendment were all efficient at reducing TP. These mesocosm s reduced TP by 60% to 73% (Table 3 1). Vegetation had a significant effect in P removal efficiency, with little difference between vegetation assemblages (Figure 3 1). Within this group of treatments with vegetation, tilling with the chemical amendment of ferric chloride provided the best reduction of TP. These tilling with amendment mesocosms resulted in an average percent reduction in TP of 69% and 73%, for subsurface soil and surface soil, respectively (Table 3 1). Soluble reactive phosphorus was measured to investigate the reduction of one of the most important fractions of phosphorus in the water, the biologically available portion. Soluble reactive phosphorus reduction ranged from 64% to 88% within all treatments (Table 3 1). The treatments without vegetation were less efficient in SRP reduction (p<0.05), with values of 65% and 64% (Figure 3 2, Table 3 1). The treatments with vegetation ranged from 80% to 88% reduction of SRP within the system (Table 3 1). No signi ficant differences (p<0.05) were

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44 observed among vegetated treatments, but the treatment with the best percent reduction of SRP was the tilling with amendment treatment (Figure 3 2). The tilling with amendment on subsurface soil reduced SRP by 84% and the t illing with amendment on surface soil reduced SRP by 88% (Table 3 1). These high reduction percentages of SRP in the vegetated treatments were due to the rapidly growing water hyacinth removing SRP directly from the water column in each mesocosm. It was hy pothesized that the elevated SRP reduction seen in the unvegetated treatments is due to algae growth in water due to light availability. Dissolved organic phosphorus was an important portion of phosphorus to monitor, as it is the portion of phosphorus whi ch can be mineralized readily to SRP. Dissolved organic phosphorus reduction within all mesocosms was moderate, ranging from 17% to 62% (Table 3 1). Patterns of DOP removal efficiency are similar to SRP and TP. The treatments void of vegetation were signif icantly lower (p<0.05) than the rest of the treatments, by providing a reduction in DOP of 17% in both subsurface soil and surface soil treatments (Figure 3 3, Table 3 1). Among the vegetated treatments DOP was reduced by 43% to 62%. Within the vegetated g roup, once again the tilling with amendment provided the highest percent reduction of DOP, with 54% and 62% reduction for subsurface soil and surface soil, respectively (Table 3 1). Particulate phosphorus is the fraction of phosphorus suspended in the wat er column that can settle out of suspension if velocity of the water is slowed. Within the mesocosms, PP was reduced by 13% to 44% in the vegetated treatments but increased in the unvegetated treatments. The unvegetated treatments had a negative reduction percentage of 55% and 112% for both subsurface soil and surface soil, respectively (Table 3 1). This production of PP in the unvegetated treatments was expected, as algae was able to grow in the mesocosms without vegetative shading, and led to a producti on of PP within the system. Within the vegetated

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45 treatments, tilling with amendment once again provided the greatest percent reduction of PP, with 38% on subsurface soil and 44% on surface soil, yet was not significantly different (p<0.05) than the other v egetated treatments (Table 3 1, Figure 3 4). Nitrogen Total Kjehldahl nitrogen was used to represent the overall reduction of nitrogen within each system. Percent reduction of TKN in the mesocosms over the study period averaged between 12 and 28 % (Table 3 2). There were less noticeable trends in the TKN reductions compared to the pronounced trends in the TP reduction values. The no vegetation treatments provided slightly lower reduction percentages than the vegetated treatments, but there was no significa nt difference (p<0.05), with values of 18 and 12 % for subsurface soil and surface soil, respectively (Table 3 2, Figure 3 5). Within the vegetated treatments, percent reduction ranged from 17 to 28 % with no significant differences between treatment types (Table 3 2, Figure 3 5). Nitrate was measured to observe the reduction in the nitrogen fraction that could be removed from the system through denitrification. Percent reduction for NO 3 within the mesocosms was very high for the treatments with vegetation present. There was a significant trend (p<0.05) in percent reduction of NO 3 between the vegetated and non vegetated treatments (Figure 3 6). The percent reduction for no vegetation treatments was 38 and 31 % for subsurface soil and surface soil treatments respectively (Table 3 2). These values were significantly smaller than the percent reduction achieved in the vegetated treatments. Within the vegetated treatments percent reduction ranged from 94 to 95 % (Table 3 2). There were no significant trends (p<0 .05) within these high percent reduction values for the vegetated treatments types (Figure 3 6). Ammonium concentrations were also monitored to represent the fraction of nitrogen which could be converted to bioavailable nitrate through nitrification with in the system. The values for percent reduction of NH 4 had no clear trends. The values for all mesocosms ranged

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46 from 2 to 24 % reduction in NH 4 (Table 3 2). The values for NH 4 varied widely between treatments, with no clear patterns and no significant dif ferences; thus, it was difficult to draw conclusions for trends in the treatment of NH 4 (Figure 3 7). Mass Removal Phosphorus To provide a value for mass removed on an area basis, inflow and outflow phosphorus concentrations were used to calculate mass of phosphorus removed per square meter per day. This value allows observation of actual retention within the system of phosphorus throughout the year, and allows for comparison to other systems. Total phosphorus, SRP, DOP, and PP mass retention was determined for each mesocosm treatment. The average mass retained in each mesocosm for TP ranged from 3.3 to 14.3 mg P m 2 day 1 (Table 3 3). Both the unvegetated treatments were significantly lower (p<0.05), with values of 3.3 mg P m 2 day 1 for subsurface soil a nd 5.3 mg P m 2 day 1 for surface soil (Table 3 3, Figure 3 8). Vegetated mesocosms had high P removal rates, ranging between 12.0 and 14.3 mg P m 2 day 1 (Table 3 3). Among the vegetated treatments there was no significant difference (p<0.05) (Figure 3 8) But the treatment to provide the highest retention of TP was the tilling with chemical amendment. These treatments provided and average TP retention of 13.3 and 14.3 mg P m 2 day 1 for subsurface soil and surface soil respectively (Table 3 3). The value s for SRP retained in the system were all relatively high, ranging from 7.7 to 10.9 mg P m 2 day 1 (Table 3 3). The difference between the vegetated treatments and unvegetated treatments was much less in the SRP values than the other fractions due to the u ptake of algae in the unvegetated mesocosms, but were still significantly different (p<0.05) (Figure 3 9). Both unvegetated systems had retention values of 7.7 and 7.9 mg P m 2 day 1 for subsurface soil and surface soil, respectively (Table 3 3). There was once again no significant

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47 difference (p<0.05) between the vegetated treatments, with all treatments ranging from 10.0 to 10.9 mg P m 2 day 1 retained in the system (Table 3 3). Among the vegetated treatments the tilling with amendment treatment performed the best, with values of 10.4 and 10.9 mg P m 2 day 1 for subsurface soil and surface soil, respectively (Table 3 3). The amount of DOP retained within the system was very small relative to TP and SRP removal. Values for DOP removal ranged from 0.4 to 2.0 mg P m 2 day 1 (Table 3 3). Similar trends exist for DOP as the other fractions, unvegetated treatments having significantly lower (p<0.05) values then the vegetated treatments (Figure 3 10). Among the vegetated treatments all mesocosms were within the sa me range, with no significant difference (p<0.05), but the tilling with the amendment had the highest removal rate (Figure 3 10). The vegetated treatments ranged from 1.4 to 2.0 mg P m 2 day 1 storage. The highest storage was attained in the tilling with a mendment treatments, with values of 1.7 and 2.0 mg P m 2 day 1 (Table 3 3). As with DOP the PP storage was relatively small, with storage rates ranging from 5.0 to 1.4 mg P m 2 day 1 (Table 3 3). The unvegetated treatments were significantly smaller then the vegetated treatments (p<0.05) (Figure 3 11). The unvegetated treatments exported PP from the system and provided negative removal rates, 5.0 and 2.4 mg P m 2 day 1 due to the growth of algae within the mesocosms without a vegetative cover. Within t he vegetated treatments there were no significant differences (p<0.05) (Figure 3 11). The highest storage values for PP were obtained by the tilling with amendment treatments, with values of 1.4 and 1.2 mg P m 2 day 1 for subsurface soil and surface soil, respectively (Table 3 3). Nitrogen The average mass of TKN removed in each mesocosm ranged from 18.2 to 41.5 mg N m 2 day 1 (Table 3 4). Within this range of values for each treatment type there were no significant t rends (p<0.05) or patterns to discern from the grouping (Figure 3 12). The highest value for

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48 TKN removed was in the tiered tilling on subsurface soil, with a value of 41.5 mg N m 2 day 1 (Table 3 4). The lowest TKN removal was found in the no vegetation on surface soil treatments, with 18.2 mg N m 2 day 1 (Table 3 4). The removal rates for NO 3 did have significant differences (p<0.05) between treatments (Figure 3 13). Within the mesocosms, the no vegetation treatments had a significantly lower removal of NO 3 compared to the removal of vegetated treatments. The no vegetation treatments had values of 7.1 and 7.6 mg N m 2 day 1 while the vegetated treatments were in the range of 20.2 to 20.5 mg N m 2 day 1 (Table 3 4). There were no significant differences (p <0.05) between the vegetated treatments for NO 3 removal (Figure 3 13). The values of NH 4 removal for all the mesocosms ranged from 2.1 to 1.1 mg N m 2 day 1 (Table 3 4). There were no significant differences (p<0.05) between treatment types in the study (Figure 3 14). These results suggest there is minimal reduction of NH 4 in the mesocosms, and that most are actually exporting small amounts of NH 4 It should be noted the values of NH 4 reduction were also highly variable. Water Chemistry Discussion Water hyacinth treatment systems have been proven to significantly improve water quality of nutrient enriched waste water. Similar water hyacinth treatment systems have been found to reduce phosphorus levels in treatment systems by as much as 93% (Reddy and DeB usk, 1985). Due to their extremely rapid growth of up to 64.4 g m 2 day 1 the phosphorus uptake rates for water hyacinth have been estimated to be as high as 243 mg P m 2 day 1 (Reddy and DeBusk, 1984; Reddy and DeBusk, 1985). For both phosphorus and nitr ogen water quality improvement the vegetated treatments performed better than the treatments devoid of vegetation. This was an expected result, as the most significant phosphorus sink in floating aquatic macrophytes systems although soil

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49 interactions can b e significant is through plant uptake during growth (Debusk and Reddy, 1987). With the rapid growth of water hyacinth, significant amounts of phosphorus are removed from the water and incorporated into the biomass of the plant. It was also an expected resu lt for reduction of nitrogen because, although large amounts of nitrogen can be removed with plant uptake, the most significant pathway for nitrogen reduction in floating aquatic macrophytes systems is through nitrification denitrification reactions in the root zone of the plants (Stowell et al. 1981; DeBusk et al. 1983; Debusk and Reddy, 1987). Within the vegetated treatments phosphorus and nitrogen water chemistry was comparable throughout, with no single treatment being significantly better in water qua lity improvement. Although it was not significantly different, the tilling with ferric chloride amendment treatments consistently performed slightly better. This was most likely due to the additional Fe + available to bind P and remove it from the system. W hile the tilling with amendment treatment did perform slightly better than the rest of the treatments, it would need to be evaluated whether the additional cost of ferric chloride amendment application would be justified for the small improvement in water quality if applied in a large scale system. With the marginal improvement in performance, the additional cost of applying ferric chloride may not be significant enough to make it financially feasible, since treatments without the amendment perform at simil ar levels. When comparing the effectiveness of this study to other treatment wetland systems, they were comparable or more effective at treating certain phosphorus and nitrogen water quality parameters. The North American Wetland Treatment System Database provides a summary of 203 treatment wetland systems, mostly surface flow marsh systems. This summary of treatment wetlands provides a measure of treatment efficiency in terms of percent concentration reduction

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50 and mass removal on an areal basis. The averag e concentration reduction percentage for TP in surface flow wetlands in North America was 57% (Kadlec and Knight, 1996). The mesocosms in this study with vegetation, which provided the best treatment, averaged 64% reduction, with a range of 60 to 73% reduc tion (Table 3 1). For mass removal on an areal basis the national average was 1.7 mg P m 2 day 1 for surface flow wetlands (Kadlec and Knight, 1996). The mesocosms with vegetation in this study out performed most surface flow wetlands for mass removal on a n areal basis with an average of 12.4 mg P m 2 day 1 and a range of 9.9 to 14.3 mg P m 2 day 1 (Table 3 3). When comparing the performance of the water hyacinth systems in this study to several other water hyacinth treatment systems in Florida, the mesoco sms in this study are similar or better at reducing total phosphorus. The mass removal of six water hyacinth treatment systems in Florida ranged from 31.0 to 142.2 mg P m 2 day 1 (DeBusk et al., 2001; Table 3 5). The vegetated mesocosms in this study range d from 9.9 to 14.3 mg P m 2 day 1 (Table 3 3 and Table 3 5). This lower treatment efficiency, based on mass removal, is due to the much lower loading rates present in this study compared to the water hyacinth systems receiving domestic wastewater (Table 3 5). Percent reduction of total phosphorus may present a more accurate comparison between the mesocosms in this study and other water hyacinth systems with much higher loading rates. The comparison of percent reduction of total phosphorus indicates the tre atment systems in this study are similar or better than some of the other water hyacinth systems in Florida. The percent reduction of the vegetated mesocosms in this study ranged from 59 to 72% (Table 3 3 and Table 3 5) while the percent reduction of compa rable water hyacinth systems was 10 to 82% (Table 3

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51 5). The percent reduction achieved in this study place the mesocosm in this study in the higher range of other successful water hyacinth based treatment systems in Florida (Table 3 5). The best compariso n between systems with different loading rates is the areal uptake rate constant (k). When using the k value for comparison between mesocosms in this study and the other water hyacinth systems in Florida, it is observed that this study is slightly better t han the median performance of the other systems. The k values for the vegetated mesocosms ranged from 24 to 34 m/yr, while the k values for the other water hyacinth systems in Florida were 3, 13, 24, 61, 67, and 99 m/yr. The mesocosms in this study were co mparable to other water hyacinth based treatment systems in Florida and achieved the goal of significant reduction of phosphorus in the inflow water. One potential adverse effect of tilling in the treatment wetland system would be a large flux of nutrients following tilling events. A flux of phosphorus from the soil might be expected, as the wetland is reflooded after the drawdown period due to the disturbance of the soil during tilling. However, the water quality data does not show a large pulse o f nutrients or a diminished treatment efficiency following each tilling event. When viewing inflow and outflow water quality on a temporal scale there are no significant long term peaks in the quality of outflow water following tilling events (Figures 3 15 to 3 21). Although there are no visible increases in outflow concentrations following each tilling event, there may be limitations in the water quality monitoring. Water was collected biweekly, which may not have been frequent enough to catch a pulse of nutrients following a tilling event. A higher frequency of water quality monitoring following tilling events may be helpful in determining any short term nutrient flux after a tilling event.

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52 It appears that the variety of tilling practices applied in this study did not have a significant influence on concentration reduction and/or mass removal. The tilling, tiered tilling, and tilling with amendment all performed at approximately similar levels of phosphorus and nitrogen removal. Soil A major constraint on the capacity of a treatment wetland to store phosphorus during the long term is its ability to accumulate new soil. The incorporation of phosphorus into the tissues of vegetation within the wetlands is the major removal mechanism utilized in treatment wet lands. The burial and accretion of this biomass and the phosphorus it contains is the only reliable and sustainable long term storage mechanism of phosphorus in wetland systems (Kadlec and Knight, 1996; Reddy et al. 1999). To maximize this long term storag e of phosphorus in the soil by increasing the rate of soil accretion while disposing of large amounts of water hyacinth biomass, the process of tilling the biomass into the soil was investigated as a potential management strategy. It is possible the proc ess of tilling water hyacinth biomass into the soil will help increase the storage rates of phosphorus and encourage more stable forms of phosphorus within the soil, while maintaining high treatment efficiency of wastewater. If there is a notable increase in organic matter content of the soil due to tilling of the water hyacinth, more phosphorus may be locked in permanent long term storage. The pools of phosphorus stored in the soil may also change as a result of tilling, with a potential increase in residu al phosphorus and other more stable forms of phosphorus with increased soil accretion rates. In a similar harvested water hyacinth system sediment was found to accrete at a rate of 1.2 cm yr 1 and P was accumulated at 1 mg m 2 d 1 (DeBusk et al. 1983; DeBu sk and Reddy, 1987). Although previous studies have investigated the accreting rates of new soil material, no study has tried to mimic this process and

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53 ecologically engineer a method that speeds up the accumulation of soil organic matter, which is importan t for long term phosphorus storage. This segment of the study aims to determine the effect tilling of biomass has on the soil properties and its associated phosphorus pools. Physico chemical Soil Properties Bulk density Bulk density was calculated for eac h soil sample throughout the study period, to observe how bulk density changed as a result of repeated tilling of biomass. The bulk density of the soils ranged from 0.91 to 1.26 g cm 3 The average bulk density of surface soil throughout the study period w as typically lower than the bulk density of subsurface soil. The average bulk density of surface soil was 1.00 g cm 3 while the average bulk density for subsurface soil was 1.10 g cm 3 (Table 3 6). As the study progressed there was a trend of decreasing soil bulk density. On average over the study period the bulk density of all soils decreased by 15.7%. The average bulk density of surface soil at the start of the study was 1.11 g cm 3 yet by the end of the study the average bulk density was 0.93 g cm 3 a 16.2% reduction in bulk density (Table 3 6). Subsurface soil started with an average bulk density of 1.22 g cm 3 and at the end of the study the average bulk density was 1.03 g cm 3 a 11.2% reduction in bulk density during the study period (Table 3 6). Changes in bulk density over the study period were all significantly different. There were no clear trends in bulk density changes between the different treatments implemented in this study. The decreases in bulk density of the soils which occurred throug h the duration of the study were expected. The bulk density of the soil would be expected to decrease through the repeated tilling and turning over of the soils. As the soil is tilled, any dense peds within the soil or any soil structure leading to a high density will be broken through the physical process of tilling.

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54 There were no soil bulk density differences between treatments. The uniformity in reduction of bulk density between treatments would be expected, because all treatments received thorough dist urbance through the tilling process. On a longer time scale, differences between treatments may become more apparent as some treatments may accumulate more organic matter and therefore have reduced bulk densities. But in the short term, as seen in this stu dy, the reduction in bulk density may possibly be attributed to the physical disturbance of tilling. pH The pH of the soils used in the study were slightly basic, but very close to neutral. Surface soil was slightly more acidic then subsurface soil, with an average pH throughout the study of 7.45 and a range of 7.27 to 7.62 (Table 3 7). Subsurface soil averaged 7.62 and ranged from 7.40 to 7.77 throughout the study period (Table 3 7). The changes in pH throughout the study were variable and somewhat spora dic. There were no clear trends between the different treatments applied in the study. There was a general and very gradual trend of increasing pH in all of the treatments. The soils on average increased slightly in pH, by 0.11, over the duration of the st udy (Table 3 7). Soil organic matter Loss on ignition (LOI) was used to estimate the percent of soil organic matter. The loss on ignition measurement was used to determine how organic matter content of the soils changed during the study as the number of tillings increased. The soil organic matter at the first sampling event of the study was compared to soil organic matter at the final sampling event. There was an increase of organic matter content in soil where water hyacinth biomass was tilled into soil In these mesocosms, the average soil organic matter for surface soil with biomass incorporation increased from 6.16% to 7.97%, a 1.81% increase in the organic matter

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55 content of the soil during the study (Table 3 8). Tilling biomass into subsurface soil i ncreased soil organic mater content from 4.32% to 5.56% (Table 3 8). The mesocosms where biomass was not tilled into the soil did not have the same increase in organic matter content as in the soils with biomass incorporation. These soils without the addi tion of vegetation remained relatively constant in soil organic matter, with a slight increase in organic matter. The treatment of no vegetation with tilling on subsurface soil started the study with an average soil organic matter content of 3.8%. Through the duration of the study the soil organic matter of these soils only slightly increased, by 0.46% to 4.32%, in organic matter content (Table 3 8). The no vegetation on surface soil treatment experienced similar results, with very small increases of organi c matter content through the study period. The no vegetation on surface soil treatment increased from an average soil organic matter of 6.05% to 6.40% for a small 0.35% increase in organic matter content of the soil (Table 3 8). The small increases in orga nic matter content of the soils not receiving biomass tilling could potentially be explained by errors in sample collection or in the lab. The small increases in organic matter could be a result of variability and be within the margin of error for loss on ignition lab methods. Throughout the duration of the study the soil organic matter of the sample soils with biomass tilling increased. This increase in soil organic matter represents an increase in the organic matter content of the mesocosm soils. As the organic matter content of the soils increases, the potential for long term storage of phosphorus is augmented. With an average increase in organic matter content of 1.81% and 1.24% for surface soil and subsurface soil, respectively, in the relatively short study period, the potential increases in organic matter content over a longer time period could be significantly large. These increases in organic matter content may encourage a large portion of the phosphorus stored in recalcitrant parts of the vegetatio n to

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56 be stored in a long term compartment within the soil. The increases in organic matter content of the soils may also help increase the phosphorus adsorption capacity of the soils. Phosphorus Forms To identify pools of phosphorus in soils, a detailed soil phosphorus fractionation was performed. This soil phosphorus fractionation identified five specific soil phosphorus pools in the soils including loosely bound or labile phosphorus (KCl extraction), Fe/Al bound phosphorus (NaOH Pi extraction), hydrolysable phosphorus or fulvic and humic bound phosphorus (NaOH Po extraction), Ca/Mg bound phosphorus (HCl extraction), and residual or recalcitrant phosphorus. The forms of phosphorus present in the soil are an important factor to consider in treatment wetlands. The pools of phosphorus in the soils can be organized into two categories, labile and non labile phosphorus. The labile forms of soil phosphorus include loosely bound or labile phosphorus, Fe/Al bo und phosphorus, and fulvic or humic bound phosphorus. The non labile forms of phosphorus include phosphorus associated with Ca/Mg and residual organic phosphorus (Reddy et al. 1995 and Debusk et al. 2004). It is preferable to have phosphorus stored in non labile forms, where they are in permanent storage and less likely to be released back to the system through desorption or mineralization. Tilling of water hyacinth biomass directly into the soil may have an impact on the forms of phosphorus being stored i n the soil. An increase in residual organic phosphorus may result from the incorporation of biomass into the soil, and may increase the storage of phosphorus in non labile forms. The composition of phosphorus pools within the soil was represented as a perc entage of soil total phosphorus. At the first sampling date of the study (5/30/07) the average phosphorus pools across all treatments were determined. The majority of phosphorus present in the soil was calcium and magnesium bound phosphorus, comprising 72. 1% of the total phosphorus. The

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57 second largest phosphorus pool was residual organic phosphorus, at 14.4%. Iron and aluminum bound phosphorus made up 7.4%, followed by fulvic and humic bound phosphorus with 6.1%. The smallest pool of phosphorus within the s oil was the labile phosphorus, with 0.1% of the total phosphorus present (Figures 3 22 to 3 29). At the end of the study (2/6/08) phosphorus pools were compared to initial values for percent change throughout the study period. During the study period ther e were no drastic changes in the composition of phosphorus within the soil. Calcium and magnesium bound phosphorus decreased by 4.3% to 67.8% of the total phosphorus. Residual phosphorus increased by 5.7% to 20.1%. Iron and aluminum bound phosphorus and fu lvic or humic bound phosphorus both decreased by 0.6% to 6.8% and 1.0% to 5.1% respectively. Labile phosphorus increased by 0.1% to 0.2% during the study (Figures 3 22 to 3 29). Similar trends were apparent when investigating changes in phosphorus pool co mposition for each treatment throughout the study. In general, all mesocosms had an increase in the proportion of phosphorus stored as residual and labile phosphorus. All treatments had a decrease in the proportion of phosphorus stored as calcium or magnes ium, with the exception of the tilled with amendment on surface soil treatment. Decreases in the proportion of fulvic and humic bound phosphorus were also noted, with the exception of the tiered tilled on subsurface soil and no vegetation on surface soil t reatments. During the study, labile phosphorus tended to increase. However, labile phosphorus fractions of soil are very small and make up much less than one percent, so the impact this fraction has on phosphorus storage in the systems is very small. The mesocosms all underwent a reduction in mass of phosphorus stored as iron and aluminum bound phosphorus. Values of the reduction in iron and aluminum bound phosphorus ranged from 1.0 to 36.5 mg/kg (Table 3 9).

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58 All soils showed a decrease in fulvic and humic bound phosphorus similar to decreases in iron and aluminum bound phosphorus. The losses in fulvic and humic bound phosphorus ranged from 5.4 to 28.0 mg/kg, with no clear patterns of loss associated with mesocosm type (Table 3 9). The soils in the mesoco sms at the beginning of the study had on average 86.5% of soil phosphorus in non labile forms and 13.5% in labile forms. At the end of the study the soils had an average of 87.9% of total phosphorus in non labile forms and 12.1% in labile phosphorus forms (Table 3 9). This small shift in proportions of phosphorus from non labile forms is encouraging for the success of tilling of water hyacinth biomass into the soil as a management strategy. The largest increase in the non labile pools was observed in the residual organic phosphorus fraction. Residual organic phosphorus on average increased by 5.7% during the study period (Table 3 9). As was hypothesized, there was an increase in residual organic phosphorus within the soils of the mesocosms. This increase i n the non labile forms of phosphorus suggests that more phosphorus is being stored on site in permanent storage. There were no clear trends when looking at the mesocosm treatment type and increases in residual organic phosphorus. It was hypothesized there would be significantly more residual organic phosphorus accrued in the treatments where water hyacinth was tilled into the soils. But this hypothesis was not supported by the data. There were increases in residual organic phosphorus pools in all mesocosms, with some of the largest increases observed in the mesocosms without vegetation tilling. It was also hypothesized there would be an increase in Fe/Al bound phosphorus in the treatments receiving the ferric chloride amendment. This was not shown by the fra ctionation data. The fractionation actually showed a reduction in proportion of the phosphorus stored, as Fe/Al bound phosphorus in these treatments. The inconsistency in this

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59 data may be a result of the tilling process and sampling. This potential source of error will be discussed further in the following section on total phosphorus storage. In addition, it could be due to natural variability and that the magnitude of effects are not significant enough to be apparent. The largest change in phosphorus pool s during the study period was found in the calcium and magnesium bound fraction. Losses in calcium and magnesium bound phosphorus ranged from 9.5 to 458.4 mg/kg, with no clear trends between mesocosms (Table 3 9). The only significant increase in a specifi c pool of phosphorus was in the residual organic phosphorus fraction. There were increases in the mass of phosphorus stored in the soil as residual phosphorus in all mesocosms during the study, except in the no vegetation on surface soil treatments. The va lues of increasing residual organic phosphorus ranged from 3.8 to 33.8 mg/kg and one decrease of 14.0 mg/kg in the no vegetation on surface soil mesocosms. Phosphorus Storage Total phosphorus was determined for each mesocosm at the beginning and end of the study period. Total phosphorus storage varied widely between treatment types, with no significant differences between treatments. The mean values for change in total phosphorus during the study period ranged from an increase of 455.5 mg/kg to a loss of 82 .0 mg/kg (Table 3 10). All treatments had an increase in phosphorus storage during the study, except for two treatment types. These were no vegetation on subsurface soil and tiered tilled on subsurface soil with losses of 51.1 mg/kg and 82.0 mg/kg, respec tively (Table 3 10). The other treatments which increased phosphorus storage had increases ranging from 112.2 to 455.5 mg/kg (Table 3 10). The values for changes in phosphorus storage varied significantly and lacked any pattern or trends. This wide range of values for changes in phosphorus storage during the study period and lack of a consistent trend might be explained by sampling error. The process of tilling the

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60 mesocosm soils may have created a very inconsistent sampling environment. As the soils were tilled, the soils and any associated phosphorus were redistributed throughout the soil profile. The tilling process may have not been uniform or consistent. This process may have led to areas of low phosphorus soils to be moved into areas of high phosphoru s soils and vice versa, leading to an inconsistent sample at different sampling points. Soil Chemistry Summary The physico chemical properties and phosphorus chemistry of the soils in the mesocosm were closely monitored throughout the duration of the stu dy. A decrease in bulk density during the study was attributed to the physical mixing of tilling and increases in organic matter content of the soils. During the study there was a significant increase in organic matter content of the soils that received ti lling of vegetation. This increase in organic matter is a positive effect of tilling water hyacinth biomass into the soils. The increase in organic matter indicated a potential increase in storage of phosphorus, as more recalcitrant organic forms within th e soils in permanent storage. The phosphorus fractionation of the soils complimented the findings of increased organic matter content of the soils by showing an increase in the percent of phosphorus stored as residual organic phosphorus. The changes in pho sphorus fractions through the duration of the study suggest a shift of phosphorus into more non labile pools as a result of tilling. Unfortunately, total phosphorus storage and some fractionation results suggest that there may have been problems with sampl ing as a result of the tilling process. Due to this potential source of error, definitive trends in the effect tilling of biomass has had on soil phosphorus dynamics are hard to distinguish. Phosphorus Budget A system mass balance for phosphorus was gen erated using water, vegetation, and soil phosphorus data for each treatment type. The system mass balance quantified the mass of

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61 phosphorus in each of several compartments on a g P m 2 basis. The individual compartments calculated for this mass balance inc luded inflow water, outflow water, phosphorus removed from water, vegetation, and soils. The mass balance was calculated as an average for each treatment type. All mesocosms received inflow water at a mass per unit area of 5.9 g P m 2 for the duration th e study (Table 3 11). The outflow of each mesocosm varied, depending on the amount of phosphorus removed from the water column. The mass removed from the water during the study period for vegetated treatments ranged from 3.5 to 4.3 g P m 2 (Table 3 11). Th e tilled with amendment treatments had the highest values for phosphorus removed from the water, with 4.0 and 4.3 g P m 2 for subsurface soil and surface soil treatments, respectively (Table 3 11, Figures 3 33 and 3 37). The treatments without vegetation r emoved far less phosphorus from the water, with 1.1 and 1.6 g P m 2 for subsurface soil and surface soil treatments, respectively (Table 3 11, Figures 3 30 and 3 34). Most of the phosphorus removed can be accounted for in phosphorus incorporated in the wat er hyacinth biomass. The amount of phosphorus stored in the vegetation ranged from 3.2 to 4.4 g P m 2 depending on plant density and phosphorus content (Table 3 11). The amount of phosphorus stored in the vegetation was an estimate based on a total of the three separate growing periods between tilling events. The phosphorus stored in vegetation accounted for 80 100% of the phosphorus removed from the water column during the study. In some cases there may have been additional phosphorus in the vegetation th at may have come from the soils, or phosphorus may have been lost from the soil as flux from the soil after tilling. The soils stored a vast majority of the phosphorus in the system. Soil phosphorus ranged from 337 to 544 g P m 2 (Table 3 11, Figures 3 30 to 3 37). The vegetation from the system was tilled into the soils. This additional phosphorus from the vegetation would only account for

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62 approximately 1% of the phosphorus in the soil. Based on this small amount of phosphorus added to the soil, relative to the mass of phosphorus already present in the soil, it would be hard to indicate an increase in phosphorus content due to the input of phosphorus from the tilled vegetation.

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63 Table 3 1. Inflow and outflow water quality data for TP, SRP, DOP, and PP with percent reduction TP* (g/L) SRP** (g/L) DOP** (g/L) PP** (g/L) Treatment Soil Type Mean S.D. % Reductio n Mea n S.D. % Reductio n Mea n S.D. % Reductio n Mea n S.D. % Reductio n Inflow 234.0 100.3 146. 5 96.3 47.5 22.8 55.1 26.1 Outflow: No Vegetation Surface 163.0 83.1 30.3 52.6 53.3 64.1 39.4 21.0 17.0 85.3 32.7 54.6 Tilling with Amendment Surface 63.1 40.2 73.0 18.4 22.0 87.5 18.2 11.0 61.7 30.8 12.3 44.2 Tilled Surface 82.9 52.6 64.6 25.2 32.9 82.8 24.4 18.5 48.6 37.0 20.3 32.8 Tiered Tilling Surface 90.4 59.3 61.4 26.8 33.0 81.7 25.8 17.6 45.7 46.6 25.8 15.6 No Vegetation Subsurface 188.9 98.1 19.3 51.7 58.4 64.7 39.0 22.2 17.8 117. 1 46.8 112.4 Tilling with Amendment Subsurface 73.7 46.5 68.5 23.3 29.9 84.1 21.8 12.5 54.0 34.1 13.9 38.1 Tilled Subsurface 93.2 68.0 60.2 28.2 37.3 80.8 27.1 20.8 43.0 47.8 28.3 13.3 Tiered Tilling Subsurface 90.7 75.8 61.2 29.4 41.5 80.0 24.9 18.7 47.5 42.0 27.7 23.9 n=3 TP period of record: 4/25/07 4/15/08; weekly samples ** SRP, DOP, and PP period record: 5/16/07 2/25/08; biweekly samples TP = Total Phosphorus SRP = Soluble Reactive Phosphorus DOP = Dissolved Organic Phosphrous PP = Particulate Phosphorus

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64 Table 3 2. Inflow and outflow water quality data for TKN, NO 3 and NH 4 with percent reduction TKN (mg/L) NO 3 (mg/L) NH 4 (mg/L) Treatment Soil Type Mean S.D. % Reduction Mean S.D. % Reduction Mean S.D. % Reduction Inflow 2.10 0.36 0.30 0.05 0.11 0.08 Outflow: No Vegetation Surface 1.86 0.30 11.6 0.21 0.06 30.9 0.12 0.09 2.1 Tilled with Amendment Surface 1.71 0.35 18.4 0.02 0.00 94.6 0.11 0.10 3.9 Tilled Surface 1.75 0.29 16.8 0.02 0.00 94.7 0.11 0.08 3.2 Tiered Tilled Surface 1.60 0.20 23.8 0.02 0.00 94.1 0.10 0.08 10.6 No Vegetation Subsurface 1.73 0.25 17.7 0.19 0.07 37.7 0.11 0.10 5.0 Tillied with Amendment Subsurface 1.62 0.39 22.8 0.02 0.00 94.4 0.09 0.08 24.4 Tilled Subsurface 1.70 0.26 19.1 0.02 0.00 94.1 0.09 0.10 20.9 Tiered Tilled Subsurface 1.51 0.26 28.2 0.02 0.00 94.2 0.10 0.09 9.9 n=3 TKN, NO 3 and NH 4 period of record: 5/10/07 2/17/08; biweekly samples TKN = Total Kjeldahl Nitrogen

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65 Table 3 3. Calculated mass removal (mg P m 2 day 1 ) for TP, SRP, DOP, and PP TP* (mg P/m/day) SRP** (mg P/m/day) DOP** (mg P/m/day) PP** (mg P/m/day) Treatment Soil Type Mean S.D. Min. Max. Mean S.D. Min. Max. Mean S.D. Min. Max. Mean S.D. Min. Ma x. No Vegetation Surface 5.3 1.8 5.4 14.2 7.7 0.3 0.0 14.1 0.3 0.3 3.0 3.3 2.4 1.6 12.5 6.2 Tilling with Amendment Surface 14.3 1.2 4.8 30.5 10.9 0.7 3.7 24.1 2.0 0.3 0.4 4.9 1.4 0.3 1.9 7.7 Tilled Surface 13.0 0.5 4.8 29.3 10.2 0.5 2.2 22.7 1.6 0.3 1.5 3.9 1.2 0.5 11.3 7.6 Tiered Tilling Surface 12.0 0.9 2.6 21.9 10.2 0.1 3.2 21.9 1.5 0.1 0.5 3.8 0.4 0.7 9.1 7.5 No Vegetation Subsurface 3.3 3.2 9.3 16.6 7.9 0.3 1.2 14.8 0.4 0.1 4.2 3.3 5.0 3.0 16.7 6.7 Tilling with Amendment Subsurface 13.3 0.5 2.8 24.7 10.4 0.2 2.8 20.5 1.7 0.1 1.4 4.8 1.2 0.7 3.7 6.9 Tilled Subsurface 9.9 4.0 3.8 20.0 10.0 0.3 2.2 20.4 1.4 0.2 2.7 4.0 0.2 0.9 11.8 7.1 Tiered Tilling Subsurface 12.1 0.2 1.0 20.6 9.9 0.5 3.0 20.2 1.5 0.2 1.1 4.5 0.6 0.5 5.2 6.9 n=3 TP period of record: 4/25/07 4/15/08; weekly samples ** SRP, DOP, and PP period record: 5/16/07 2/25/08; biweekly samples TP = Total Phosphorus SRP = Soluble Reactive Phosphorus DOP = Dissolved Organic Phosphrous PP = Particulate Phosphorus

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66 Table 3 4. Calculated mass removal (mg P m 2 day 1 ) for TKN, NO 3 and NH 4 TKN (mg P/m/day) NO 3 (mg P/m/day) NH 4 (mg P/m/day) Treatment Soil Type Mean S.D. Min. Max Mean S.D. Min. Max. Mean S.D. Min. Max. No Vegetation Surface 18.2 8.7 20.3 45.0 7.1 0.8 1.2 11.9 1.9 4.3 31.1 13.0 Tilled with Amendment Surface 27.9 5.8 14.2 70.2 20.4 0.1 13.7 26.4 1.8 8.2 42.4 18.4 Tilled Surface 21.6 7.2 20.2 67.9 20.5 0.1 13.3 26.4 2.1 7.9 37.3 11.0 Tiered Tilled Surface 34.3 8.4 3.0 73.3 20.3 0.1 13.3 25.6 0.7 4.1 26.7 18.7 No Vegetation Subsurface 24.7 16.7 22.5 76.9 7.6 0.2 0.4 16.6 1.4 6.3 48.0 17.9 Tilled with Amendment Subsurface 35.1 5.4 2.4 62.1 20.3 0.1 13.3 26.0 1.1 4.6 30.4 13.1 Tilled Subsurface 24.9 4.1 4.0 73.5 20.2 0.1 13.4 26.4 0.9 8.4 38.9 14.9 Tiered Tilled Subsurface 41.5 1.3 23.1 71.6 20.3 0.1 13.3 26.0 1.7 2.7 19.9 15.6 n=3 TKN, NO 3 and NH 4 period of record: 5/10/07 2/17/08; biweekly samples TKN = Total Kjeldahl Nitrogen

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67 Table 3 5. Summary of water hyacinth treatment systems performance in Florida with summary of study wetlands (data from Stewart et al. 1987). Treatment Wetland or Treatment Type Soil Type HLR (cm/day) Influent (mg/L) Effluent (mg/L) P Loading (g/m2 yr) P Loading (mg/m2 day) P Removal (g/m2 yr) P Removal (mg/m2 day) % TP removal k Coral Springs 7 4.68 4.23 116.0 317.8 11.3 31.0 10 3 Melbourne 22 4.33 3.70 354.0 969.9 51.5 141.1 15 13 Kissimmee 4 1.46 0.27 20.8 57.0 16.9 46.3 82 24 Loxahatchee 28 1.06 0.55 108.0 295.9 51.9 142.2 48 67 Iron Bridge 1 21 0.74 0.33 56.2 154.0 29.6 81.1 55 61 Iron Bridge 2 25 0.30 0.10 26.9 73.7 18.0 49.3 67 99 No Vegetation Surface 7 0.23 0.16 6.3 17.2 1.9 5.3 29 9 Tilling with Amendment Surface 7 0.23 0.06 6.3 17.2 5.2 14.3 72 34 Tilled Surface 7 0.23 0.08 6.3 17.2 4.7 13.0 64 27 Tiered Tilling Surface 7 0.23 0.09 6.3 17.2 4.4 12.0 61 24 No Vegetation Subsurface 7 0.23 0.19 6.3 17.2 1.2 3.3 18 6 Tilling with Amendment Subsurface 7 0.23 0.07 6.3 17.2 4.9 13.3 68 30 Tilled Subsurface 7 0.23 0.09 6.3 17.2 3.6 9.9 59 24 Tiered Tilling Subsurface 7 0.23 0.09 6.3 17.2 4.4 12.1 60 24

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68 Table 3 6. Bulk density of soils throughout study period Sample 1 (g/cm 3 ) Sample 2 (g/cm 3 ) Sample 3 (g/cm 3 ) Treatment Soil Type Mean S.D. Mean S.D. Mean S.D. No vegetation Surface 1.06 0.03 0.94 0.07 0.91 0.07 Tilled with amendment Surface 1.15 0.08 0.99 0.04 0.95 0.04 Tilled Surface 1.06 0.05 0.93 0.04 0.91 0.03 Tiered tilled Surface 1.17 0.05 1.00 0.02 0.95 0.02 No vegetation Subsurface 1.24 0.05 1.04 0.04 1.03 0.03 Tilled with amendment Subsurface 1.26 0.06 1.08 0.08 1.01 0.01 Tilled Subsurface 1.21 0.05 1.02 0.06 1.04 0.03 Tiered tilled Subsurface 1.17 0.03 1.05 0.03 1.04 0.02 n=3 Sample 1 = 5/30/2007 Sample 2 = 9/20/2007 Sample 3 = 2/6/2008

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69 Table 3 7. pH of soils throughout study period Sample 1 Sample 2 Sample 3 Treatment Soil Type Mean S.D. Mean S.D. Mean S.D. No vegetation Surface 7.4 0.0 7.3 0.4 7.6 0.1 Tilled with amendment Surface 7.4 0.1 7.4 0.4 7.4 0.3 Tilled Surface 7.3 0.1 7.6 0.2 7.5 0.2 Tiered tilled Surface 7.5 0.2 7.3 0.2 7.6 0.2 No vegetation Subsurface 7.6 0.1 7.7 0.0 7.6 0.0 Tilled with amendment Subsurface 7.7 0.1 7.7 0.1 7.8 0.0 Tilled Subsurface 7.6 0.1 7.6 0.2 7.7 0.1 Tiered tilled Subsurface 7.4 0.4 7.6 0.1 7.5 0.5 n=3 Sample 1 = 5/30/2007 Sample 2 = 9/20/2007 Sample 3 = 2/6/2008

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70 Table 3 8. Loss on ignition of soils throughout study period Sample 1 (%) Sample 2 (%) Sample 3 (%) Treatment Soil Type Mean S.D. Mean S.D. Mean S.D. No vegetation Surface 6.1 0.2 6.4 0.2 6.4 0.1 Tilled with amendment Surface 6.2 0.6 7.8 0.9 8.0 1.3 Tilled Surface 6.1 0.3 7.7 0.7 7.7 1.1 Tiered tilled Surface 6.2 0.9 7.9 0.4 8.2 0.6 No vegetation Subsurface 3.9 0.6 4.2 0.1 4.3 0.6 Tilled with amendment Subsurface 4.7 0.9 5.4 0.7 5.9 1.2 Tilled Subsurface 3.9 0.4 4.6 0.5 5.8 1.1 Tiered tilled Subsurface 4.3 1.3 4.9 0.3 5.0 0.7 n=3 Sample 1 = 5/30/2007 Sample 2 = 9/20/2007 Sample 3 = 2/6/2008

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71 Table 3 9. Soil phosphorus fractionation data summary Initial Soils (mg/kg) Final Soils (mg/kg) Change (mg/kg) Treatment Soil P Fraction Mean S.D. Mean S.D. KCl Pi 0.7 0.2 1.4 1.0 0.7 NaOH Pi 82.8 58.5 46.3 12.0 36.5 No Vegetation on Surface Soil NaOH Po 68.5 35.5 56.1 18.6 12.5 HCl Pi 732.4 35.9 274.0 143.7 458.4 Residual Po 153.5 36.9 139.5 15.9 14.0 KCl Pi 0.5 0.1 1.1 0.8 0.6 NaOH Pi 45.7 14.6 43.1 7.9 2.7 Tilled with Amendment on Surface Soil NaOH Po 47.9 9.5 35.7 3.9 12.2 HCl Pi 504.9 96.2 495.4 143.3 9.5 Residual Po 115.5 3.0 119.3 12.6 3.8 KCl Pi 1.3 0.3 1.6 0.5 0.3 NaOH Pi 73.9 29.0 50.5 12.8 23.4 Tilled on Surface Soil NaOH Po 64.4 22.7 38.9 7.7 25.5 HCl Pi 572.2 57.4 470.7 249.2 101.4 Residual Po 138.7 14.4 142.5 24.2 3.8 KCl Pi 0.7 0.2 1.2 0.3 0.4 NaOH Pi 54.8 20.8 44.6 5.7 10.2 Tiered Tilled on Surface Soil NaOH Po 58.3 16.8 30.3 9.4 28.0 HCl Pi 593.3 406.3 530.6 204.4 62.7 Residual Po 124.7 38.5 158.5 23.0 33.8 KCl Pi 0.5 0.1 1.1 0.5 0.6 NaOH Pi 54.9 2.9 35.2 6.1 19.7 No Vegetation on Subsurface Soil NaOH Po 35.6 5.7 16.7 9.2 18.9 HCl Pi 538.4 43.6 344.9 112.0 193.5 Residual Po 98.4 8.2 109.3 14.1 10.9 KCl Pi 0.5 0.1 1.2 0.3 0.7 NaOH Pi 65.1 20.8 43.2 11.2 21.9 Tilled with Amendment on Subsurface Soil NaOH Po 51.7 24.7 34.9 31.2 16.8 HCl Pi 610.9 72.4 458.1 205.0 152.7 Residual Po 109.0 11.3 122.6 10.5 13.6 KCl Pi 0.9 0.5 1.0 0.4 0.2 NaOH Pi 50.4 16.6 49.4 5.1 1.0 Tilled on Subsurface Soil NaOH Po 34.9 6.0 22.1 4.5 12.9 HCl Pi 508.6 125.1 477.4 90.3 31.2 Residual 101.4 13.0 131.5 8.9 30.1

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72 Po Table 3 9. Continued Initial Soils (mg/kg) Final Soils (mg/kg) Change (mg/kg) Treatment Soil P Fraction Mean S.D. Mean S.D. KCl Pi 1.0 0.5 1.6 1.1 0.7 NaOH Pi 56.2 1.6 45.6 6.0 10.6 Tiered Tilled on Subsurface Soil NaOH Po 38.6 8.8 33.2 25.4 5.4 HCl Pi 682.2 260.7 510.6 258.0 171.6 Residual Po 103.4 13.8 129.8 18.9 26.4 n=3 KCl Pi = Labile phosphorus NaOH Pi = Fe/Al bound phosphorus NaOH Po = Fulvic and humic bound phosphorus HCl Pi = Ca/Mg bound phosphorus Residual Po = Residual organic phosphorus

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73 Table 3 10. Total phosphorus of soils throughout study period Initial Soils (mg/kg) Final Soils (mg/kg) Change (mg/kg) Treatment Soil Type Mean S.D. Mean S.D. No Vegetation Surface 734 133 1137 539 404 Tilled with Amendment Surface 659 27 800 171 141 Tilled Surface 889 757 1052 214 163 Tiered Tilled Surface 849 175 961 439 112 No Vegetation Subsurface 710 206 659 116 51 Tillied with Amendment Subsurface 672 56 1087 547 415 Tilled Subsurface 910 325 828 231 82 Tiered Tilled Subsurface 560 61 1016 244 455 n=3

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74 Table 3 11. Phosphorus mass balance of system for duration of study Treatment Soil Type Inflow Water (g/m 2 ) Outflow Water (g/m 2 ) Removed from Water (g/m 2 ) Vegetation (g/m 2 ) Soils (g/m 2 ) No Vegetation Surface 5.9 4.3 1.6 507.2 Tilled with Amendment Surface 5.9 1.6 4.3 3.8 368.6 Tilled Surface 5.9 2.1 3.8 4.3 428.6 Tiered Tilled Surface 5.9 2.3 3.6 3.8 502.7 No Vegetation Subsurface 5.9 4.8 1.1 337.0 Tillied with Amendment Subsurface 5.9 1.9 4.0 3.2 544.0 Tilled Subsurface 5.9 2.4 3.5 4.4 526.4 Tiered Tilled Subsurface 5.9 2.3 3.6 3.5 430.5 n=3

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75 Figure 3 1. Statistical ANOVA plot of TP mass reduction percent (%). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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76 Figure 3 2. Statistical ANOVA plot of SRP mass reduction percent ( %). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on sub surface soil, and TTS= tiered till on surface soil.

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77 Figure 3 3. Statistical ANOVA plot of DOP mass reduction percent (%) NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= ti lled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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78 Figure 3 4. Statistical ANOVA plot of PP mass reduction percent (%). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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79 Figure 3 5. Statistical ANOVA plot of TKN mass reduction percent (%). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with ame ndment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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80 Figure 3 6. Statistical ANOVA plot of NO 3 mass reduction percent (%). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tier ed till on surface soil.

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81 Figure 3 7. Statistical ANOVA plot of NH 4 mass reduction percent (%). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surf ace soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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82 Figure 3 8. Statistical ANOVA plot of TP mass removal (mg P m 2 day 1 ). NVSS= no vegetation on subsurface s oil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on s urface soil.

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83 Figure 3 9. Statistical ANOVA plot of SRP mass removal (mg P m 2 day 1 ). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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84 Figure 3 10. Statistical ANOVA plot of DOP mass removal (mg P m 2 day 1 ). NVSS= no vegetation on subsurface soil, NV S= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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85 Figure 3 11. Statistical ANOVA plot of PP mass removal (mg P m 2 day 1 ). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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86 Figure 3 12. Statistical ANOVA plot of TKN mass removal (mg P m 2 day 1 ). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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87 Figure 3 13. Statistical ANOVA plot of NO 3 mass removal (mg P m 2 day 1 ). NVSS= no vegetation on subsurface soil, NVS= no vegetation on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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88 Figure 3 14. Statistical ANOVA plot of NH 4 mass removal (mg P m 2 day 1 ). NVSS= no vegetation on subsurface soil, NVS= no vegeta tion on surface soil, TASS= tilled with amendment on subsurface soil, TAS= tilled with amendment on surface soil, TSS= tilled on subsurface soil, TS= tilled on surface soil, TTSS= tiered till on subsurface soil, and TTS= tiered till on surface soil.

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89 Figure 3 15. TP water quality throughout study period. A = No vegetation with tilling, B = Tilled, C = Tilled with chemical amendment, D = Tiered tilled. Tilling dates were 5/30/07, 9/20/07, and 2/6/08

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90 Figure 3 16. SRP water quality throughout study period. A = No vegetation with tilling, B = Tilled, C = Tilled with chemical amendment, D = Tiered tilled. Tilling dates were 5/30/07, 9/20/07, and 2/6/08

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91 Figure 3 17. DOP water quality throughout study period. A = No vegetation with til ling, B = Tilled, C = Tilled with chemical amendment, D = Tiered tilled. Tilling dates were 5/30/07, 9/20/07, and 2/6/08

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92 Figure 3 18. PP water quality throughout study period. A = No vegetation with tilling, B = Tilled, C = Tilled with chemical amendment D = Tiered tilled. Tilling dates were 5/30/07, 9/20/07, and 2/6/08

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93 Figure 3 19 TKN water quality throughout study period. A = No vegetation with tilling, B = Tilled, C = Tilled with chemical amendment, D = Tiered tilled. Tilling dates were 5/30/07, 9/ 20/07, and 2/6/08

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94 Figure 3 20 NO 3 water quality throughout study period. A = No vegetation with tilling, B = Tilled, C = Tilled with chemical amendment, D = Tiered tilled. Tilling dates were 5/30/07, 9/20/07, and 2/6/08

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95 Figure 3 21 NH 4 water quality throughout study period. A = No vegetation with tilling, B = Tilled, C = Tilled with chemical amendment, D = Tiered tilled. Tilling dates were 5/30/07, 9/20/07, and 2/6/08

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96 Figure 3 22. Ini tial and final no vegetation on surface soils phosphorus fractionation percent of total phosphorus Figure 3 23. Initial and final tilled on surface soils phosphorus fractionation percent of total phosphorus

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97 Figure 3 24. Initial and final tilled with am endment on surface soils phosphorus fractionation percent of total phosphorus Figure 3 25. Initial and final tiered tilled on surface soils phosphorus fractionation percent of total phosphorus

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98 Figure 3 26. Initial and final no vegetation on subsurface soils phosphorus fractionation percent of total phosphorus Figure 3 27. Initial and final tilled on subsurface soils phosphorus fractionation percent of total phosphorus

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99 Figure 3 28. Initial and final tilled with amendment on subsurface soils phosphoru s fractionation percent of total phosphorus Figure 3 29. Initial and final tiered tilled on subsurface soils phosphorus fractionation percent of total phosphorus

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100 Figure 3 30. Diagram of No Vegetation on Surface Soil (NVS) treatment mass balance and pho sphorus distribution within the system for one year. Figure 3 31. Diagram of Tilled on Surface Soil (TS) treatment mass balance and phosphorus distribution within the system for one year.

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101 Figure 3 32. Diagram of Tiered Tilled on Surface Soil (TTS) tr eatment mass balance and phosphorus distribution within the system for one year. Figure 3 33. Diagram of Tilled with Amendment on Surface Soil (TAS) treatment mass balance and phosphorus distribution within the system for one year.

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102 Figure 3 34. Diagra m of No Vegetation on Subsurface Soil (NVSS) treatment mass balance and phosphorus distribution within the system for one year. Figure 3 35. Diagram of Tilled on Subsurface Soil (TSS) treatment mass balance and phosphorus distribution within the system for one year.

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103 Figure 3 36. Diagram of Tiered Tilled on Subsurface Soil (TTSS) treatment mass balance and phosphorus distribution within the system for one year. Figure 3 37. Diagram of Tilled with Amendment on Subsurface Soil (TASS) treatment mass bal ance and phosphorus distribution within the system for one year.

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104 CHAPTER 4 SUMMARY AND CONCLUSI ONS In order to evaluate the feasibility and functioning of tilling water hyacinth biomass into the onsite soils as a viable management strategy for maintenance of floating macrophyte treatment systems, a mesocosm study was established. This study was designed to specifically investigate how tilling practices influence treatment efficiency and soil phosphorus dynamics. The mesocosm study evaluated how organic matter accumulation rates were influenced, how soil phosphorus forms were changed as a function of time and the stability of these soil phosphorus pools. It was found that all of the vegetated mesocosms successfully reduced incoming phosphorus concentrations. All forms of phosphorus were reduced significantly. On average the vegetated treatments reduced t otal phosphorus by 64%, with a maximum reduction of 72.5%. The vegetated treatments were found to have an average mass reduction of 12.4 mg P m 2 day 1 with a maximum mass reduction of 14.3 mg P m 2 day 1 The unvegetated treatments had a significantly lo wer phosphorus reduction, which was expected as vegetation uptake is a key process in floating macrophyte treatment systems. Among the vegetated treatments there were no significant differences in water quality improvement, although the tilling with amendm ent treatments consistently had the highest phosphorus reduction. It is clear that the systems with tilling are effectively reducing phosphorus with no adverse effect from tilling. Within the soil several key findings suggest tilling of water hyacinth may be an effective method for management of water hyacinth biomass, while increasing the onsite long term storage of phosphorus. Bulk density was decreased throughout the duration of the study. On average the bulk density of the mesocosm soils decreased by 15 .7% during the study period. This decrease in bulk density was most likely due to the tilling process and an increase in organic

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105 matter. To investigate increases in organic matter, the loss on ignition was determined throughout the study. The loss on ignit ion data suggests there was an increase of 1.81% and 1.24% in organic matter, respectively, for surface soil and subsurface soil with vegetation tilling. The treatments without the vegetation tilling had significantly lower increases in organic matter cont ent during the study. This increase in organic matter content of the soils with vegetation tilling was seen over a one year period. If extrapolated for several years the increases in soil organic matter may become very pronounced. Increases in organic matt er can have significant impacts on phosphorus treatment and storage of phosphorus in long term pools within the soil, as it is the only reliable long term phosphorus storage mechanism of wetlands. To investigate the influence tilling of water hyacinth biom ass has on soil phosphorus pools, a detail phosphorus fractionation was performed. The phosphorus fractionation classified the soil phosphorus as readily available phosphorus (KCl Pi extraction), Fe/Al bound phosphorus (NaOH Pi extraction), fulvic and humi c bound phosphorus (NaOH Po extraction), Ca/Mg bound phosphorus (HCl extraction), and residual organic phosphorus. The fractionation found on average 67.8% of the phosphorus in the soil was Ca/Mg bound phosphorus, 20.1% was residual organic phosphorus, 6.8 % was Fe/Al bound phosphorus, 5.1% was fulvic and humic bound phosphorus, and 0.2% was readily available phosphorus. Through the duration of the study the soils shifted a small amount, from 86.5% to 87.9% phosphorus stored in non labile forms. The largest increase in any one phosphorus fraction in the soils was a 5.7% increase in residual organic phosphorus. This increase in residual organic phosphorus was expected, as the tilled vegetation has also increased the organic matter content. The increases in res idual organic phosphorus suggest more phosphorus is being stored in the long term soil phosphorus pools. When investigating total phosphorus storage and changes during the study, the results were

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106 highly variable and no trends or patterns could be determine d. This may be a result of a sampling error due to the highly volatile and inconsistent soil environment caused by the tilling of the soils. There does not appear to be significant differences in the various types of tilling performed during the study. Alt hough the tilling with amendment consistently had higher treatment efficiencies, it was not significantly better then the other tilling methods. If the management strategy of tilling water hyacinth into the soils were applied on a large scale system, it ma y be beneficial to implement the lowest cost and less time intensive method of regular tilling rather than the tilling with amendment or tiered tilling. The results of this study suggest tilling of water hyacinth biomass may be an effective management stra tegy for floating macrophytes treatment systems. Water quality monitoring has shown the systems with tilling of water hyacinth are efficient in reducing both phosphorus and nitrogen concentrations in the inflow water. Tilling has not adversely affected the reduction of the different phosphorus and nitrogen species in the mesocosms. Soils data suggest the tilling processes may encourage the storage of phosphorus in more recalcitrant or non labile forms in the soil and increase the organic matter content of t he soils. This increase in the organic matter and residual organic phosphorus fraction may lead to more of the phosphorus removed from the water column being locked in long term storage and prevented it from reaching natural downstream systems.

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107 L IST OF REFERENCES Crites, R. W. and T. J. Mingee. 1987. Economics of aquatic wastewater treatment systems. In. K. R. Reddy and W.H. Smith (ed.) Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing Inc., Orlando FL. DeBusk, T. A., M. D. Hanisak, L. D. Williams, and J. H. Ryther. 1981. Effects of seasonality and plant density on the productivity of some freshwater macrophytes. Aquat. Bot. 10, 133 143. DeBusk, T. A., L. D. Williams, and J. H. Ryther. 1983. Removal of nitrogen and phos phorus from wastewater in a water hyacinth based treatment system. J. Environ. Qual. 12: 133 143. DeBusk, T. A. and K. R. Reddy. 1987. Wastewater Treatment Using Floating Aquatic Macrophytes: Contaminant Removal Processes and Management Strategies. P. 643 656. In. K. R. Reddy and W.H. Smith (ed.) Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing Inc., Orlando FL. DeBusk, T. A., K. R. Reddy, T. D. Hayes, and B. R. Schweigler Jr. 1989. Performance of a pilot scale water hyacinth based secondary treatment system. J. Water Pollut. Control Fed., 61, 1271. DeBusk, T. A. and K. R. Reddy. 1989. Wastewater nutrient removal in Florida using aquatic macrophytes. In Proceedings, Biological Nitrogen and Phosphorus Removal: The Florida Exper ience II. University of Florida TREEO Center, Gainesville, FL, USA. DeBusk, T. A., Peterson, J. E., and Reddy, K. R. 1996. Use of aquatic and terrestrial plants for removing phosphorus from dairy wastewaters. Ecol. Eng. 5, 371 390. DeBusk, T. A. and F. E. Dierberg. 1999. Techniques for Optimizing Phosphorus Removal in Treatment Wetlands. P. 467 488. In. K. R. Reddy et al. (ed.) Phosphorus biogeochemistry in subtropical ecosystems. Lewis Publ., Boca Raton, FL. DeBusk, T. A., F. E. Dierberg, and K. R. Reddy. 2001. The use of macrophyte based systems for phosphorus removal: an overview of 25 years of research and operational results in Florida. Water Science and Technology Vol. 44 No 11 12 pp 39 46. DeBusk, T. A., K. A. Grace, F. E. Dierberg, S. D. Jackson, M. J. Chimney, and B. Gu. 2004. An investigation of the limits of phosphorus removal in wetlands: a mesocosm study of a shallow periphyton dominated treatment system. Ecological Engineering 23: 1 14 DeBusk, T. A.2005. Evaluation of passive and actively manage d treatment wetlands for phosphorus removal from dairy and basin wide runoff. In. Phosphorus Retention and Storage by Isolated and Constructed Wetlands in the Okeechobee Drainage Basin Annual Report, submitted to University of Florida and Florida Departme nt of Agriculture and Consumer Services.

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108 Duffer, W. R. 1982. Assessment of aquaculture for reclamation of wastewater. In. E. Joe Middlebrooks (ed.) Water Reuse. Ann Arbor Science Publishers Inc., Ann Arbor, Mi. Diaz, O. A., K. R. Reddy, and P. A. Moore, J r. 1994. Solubility of inorganic P in stream water as influenced by pH and Ca concentration Water Res. 28:1755 1763. Fisher, M. M. and Reddy, K. R.1987. Water hyacinth ( Eichhornia crassipes [Mart] Solms) for improving eutrophic lake water: water quality a nd mass balance. In. K. R. Reddy and W.H. Smith (ed.) Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing Inc., Orlando FL. Fisher M. M. and K. R. Reddy. 2001 Phosphorus flux from wetland soils affected by long term nutrient loading, J. Environ. Qual. 30 : 261 271. Hayes, T. D., H. R. Isaacson, K. R. Reddy, D. P. Chynoweth, and R. Biljetina. 1987. Water hyacinth system for water treatment. In. K. R. Reddy and W .H. Smith (ed.) Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing Inc., Orlando FL. House, W. A., and L. Donaldson. 1986. Adsorption and coprecipitation of phosphate on calcite. J. Coloid Interface Science. 112:309 324. Kadlec, R.H. and R.L. Knight. 1996. Treatment Wetlands. CRC Press LLC, Boca Raton,FL McLatchey G.P. and K.R. Reddy, Regulation of organic matter decomposition and nutrient release in a wetland soil, J. Environ. Qual. 27 : 1268 1274. Mitsch, W. J. and J.G. Gosselin k. 2000. Wetlands. 3 rd edition. John Wiley and Sons, Inc, New York. Nichols, D. S. 1983. Capacity of natural wetlands to remove nutrients from waterwater. J. Water Pollut. Control Fed. 55:495. Reddy, K. R. 1983. Fate of nitrogen and phosphorus in a waste water retention reservoir containing aquatic macrophytes. J. Environ. Qual. 12, 137. Reddy, K. R., Sutton, D. L., and Bowes, G. 1983. Freshwater aquatic plant biomass production in Florida. Proc. Soil and Crop Sci. Soc. Florida, 42, 28 40. Reddy, K. R., an d W. F. DeBusk. 1984. Growth characteristics of aquatic macrophytes cultured in nutrient enriched water: I. water hyacinth, water lettuce, and pennywort. Econ. Bot. 38: 229 239. Reddy, K. R., and Sutton, D. L. 1984. Water hyacinth for water quality improve ment and biomass production. J. Environ. Qual. 13, 1. Reddy, K. R., and W. F. DeBusk. 1985. Nutrient removal potential of selected aquatic macrophytes. J. Environ. Qual. 14, 459 462.

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109 Reddy, K. R., and W. F. DeBusk. 1987. Nutrient storage capabilities of a quatic and wetland plants. In. K. R. Reddy and W.H. Smith (ed.) Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing Inc., Orlando FL. Reddy, K. R., R. D. DeLaune, W. F. DeBusk, and M. S. Koch. 1993. Long term nutrient accumulation rates in the Everglades. Soil Sci. Soc. Am. J. 57:1147 1155. Reddy, K. R., O. A. Diaz, L. J. Scinto, and M. Agami. 1995. Phosphorus dynamics in selected wetlands and streams of the lake Okeechobee Basin. Ecological Engineering 5:183 207. Reddy, K. R., R. H. Kadlec, E. Flaig, and P. M. Gale. 1999. Phosphorus retention in streams and wetlands: A Review. Critical Reviews in Environmental Science and Technology 29: 83 146. Reddy, K. R., R. G. Wetzel, and R. H. Kadlec. 2005. Biogeochemistry of Phosphorus in Wet lands. P. 263 314. In. Phosphorus: Agriculture and the Environment. American Society of Agronomy. Reddy, K. R. and R. D. DeLaune. 2009. Biogeochemistry of Wetlands: Science and Applications. CRC Press, Boca Raton, FL. Rhue, R. D., and W. G. Harris. 1999. P hosphorus sorption/desorption reactions in soil and sediments. P. 187 206. In. K. R. Reddy et al. (ed.) Phosphorus biogeochemistry in subtropical ecosystems. Lewis Publ., Boca Raton, FL. Richardson, C. J. and P.E. Marshall. 1986. Processes controlling move ment, storage, and export of phosphorus in a fen peatland, Ecol. Monogr. 56 : 279 302. Richardson, C. J. and C. B. Craft. 1993. Effective Phosphorus Retention in Wetlands: Fact or Fiction? P. 271 282. In. Gerald A. Moshiri. Constructed Wetlands for Water Qu ality Improvement. Lewis Publ., Boca Raton, FL. Richardson, C. J. 1999. The role of wetlands in storage, release, and cycling if phosphorus on the landscape: A 26 year retrospective. p. 69 110. In. K. R. Reddy et al. (ed.) Phosphorus biogeochemistry in sub tropical ecosystems. Lewis Publ., Boca Raton, FL. Stewart, E. A., Haselow, D. L., and Wyse, N. M. 1987. Review of operations and performance data on five water hyacinth based treatment systems in Florida. In. K. R. Reddy and W.H. Smith (ed.) Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing Inc., Orlando FL. Stowell, R., R. Ludwig, J. Colt, and T. Tchobanohlous. 1981. Concepts in aquatic treatment design. Pp. 919 940. Proc. Am. Soc. Civ. Eng., Vol. 107, Bo EE5, October 1981. Tha baraj, G. J. 1987. Water hyacinths for wastewater treatment in Florida: prospects and constraints. In. K. R. Reddy and W.H. Smith (ed.) Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing Inc., Orlando FL.

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110 BIOGRAPHICAL SKETCH Co ry Catts was born in Bradenton, FL, in 1983 Growing up, Cory fostered an interest and love for the environment. From an early age he was sure he wanted a career in the environmental science field. Afte r graduating high school in 2001, he attended the Univ ersity of Florida in Gainesville, FL. H e g raduated magna cum laude in 2005 with a bachelor's degree in environmental science, with a minor in soil and water science. During his time at the University of Florida he became interested in the study of wetlands ecology. His interest in wetlands and water quality issues led him to pursue a at the University of Florida in 2006. Cory is currently employed by the South We st Florida Water Management District.