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Determination of Aqueous Soil Sorption Coefficient (Koc) of Strongly Hydrophobic Organic Chemicals (SHOCs) Using Mixed S...

Permanent Link: http://ufdc.ufl.edu/UFE0021819/00001

Material Information

Title: Determination of Aqueous Soil Sorption Coefficient (Koc) of Strongly Hydrophobic Organic Chemicals (SHOCs) Using Mixed Solvent Systems and the Solvophobic Model
Physical Description: 1 online resource (76 p.)
Language: english
Creator: Muwamba, Augustine
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: aqueous, carbonatic, hydrocarbonaceous, hydrophobic, lipophilic, organic, solvophobic, sorption, spodosol, teflon
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: Determination of the sorption coefficients (Koc) of strongly hydrophobic organic chemicals (SHOCs) in aqueous systems is difficult due to their very low solubility and the potential to adsorb on container walls and vessels. ?-endosulfan, dieldrin, DDT, and anthracene were used in this study as probe compounds. Sorption of dieldrin and ?-endosulfan on Teflon lined centrifuge tubes (TLCT) and HPLC vials (HPLCV) was measured in methanol-water systems. Similarly, DDT and anthracene sorption on TLCT was also measured. The volume fraction of methanol (fc) ranged from 0.01to 1. The solution concentrations of 12C-dieldrin and 12C-?-endosulfan were analyzed using high pressure liquid chromatography (HPLC) with UV detection. Liquid scintillation counting (LSC) was used to measure solution concentrations of 14C-DDT and 14C-anthracene. The container sorption coefficients (KW) in aqueous systems were obtained by use of the Solvophobic model and extrapolating the sorption coefficient to zero fraction cosolvent (fc = 0). Using the Solvophobic model, the calculated percent recovery of ?-endosulfan due to sorption on TLCT and HPLCV in aqueous system was 30%. Dieldrin recovery at fc = 0 was 6 and 32% from HPLCV and TLCT, respectively. DDT adsorbed most on TLCT followed by dieldrin and least anthracene, with calculated recoveries in aqueous system of 29, 32, and 52%, respectively. Negligible adsorption was detected for dieldrin at fc ? 0.45 in TLCT and at fc ? 0.70 in HPLCV. Similarly negligible adsorption was detected for DDT and anthracene at fc ? 0.45 in TLCT. It is important to point out that most researchers assume that Teflon lined centrifuge tubes and HPLC vials do not adsorb organic chemicals. The sorption coefficients of dieldrin, DDT, and anthracene by 3 carbonatic soils, one organic soil, and one spodosol, were then determined in methanol-water systems that eliminated sorption on the TLCT and HPLCV. The soil sorption coefficients (KW) in aqueous systems were extrapolated at volume fraction methanol (fc = 0). The KW values were then normalized with soil organic carbon content (OC) to obtain KOC = KM/OC values. The KOC values for DDT, dieldrin, and anthracene obtained in this study were much lower than literature values and did not drastically vary across soil as it is reported in the literature. The KOC values for dieldrin obtained in this study varied within a factor of 2 compared to the literature factor of 4. For DDT, the KOC values varied within a factor of 4 compared to the reported literature factor of 13. The KOC data from this study strongly indicate that sorption on container walls if neglected is a potential source of error while determining adsorption of strongly hydrophobic chemicals in aqueous systems. It is therefore recommended that sorption experiments of strongly hydrophobic chemicals be carried out in TLCT above 45% cosolvent in a mixture with water and at and above 70% cosolvent in HPLC vials. The sorption coefficients in aqueous systems can then be calculated using the Solvophobic model eliminating errors due to sorption on container walls and over estimation of sorption coefficients. The hydrocarbonaceous surface area (HSA) of SHOCs calculated from sorption on TLCT, HPLCV, and by soils gave similar values as predicted by the Solvophobic theory.
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 Augustine Muwamba.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Nkedi-Kizza, Peter.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021819:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021819/00001

Material Information

Title: Determination of Aqueous Soil Sorption Coefficient (Koc) of Strongly Hydrophobic Organic Chemicals (SHOCs) Using Mixed Solvent Systems and the Solvophobic Model
Physical Description: 1 online resource (76 p.)
Language: english
Creator: Muwamba, Augustine
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: aqueous, carbonatic, hydrocarbonaceous, hydrophobic, lipophilic, organic, solvophobic, sorption, spodosol, teflon
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: Determination of the sorption coefficients (Koc) of strongly hydrophobic organic chemicals (SHOCs) in aqueous systems is difficult due to their very low solubility and the potential to adsorb on container walls and vessels. ?-endosulfan, dieldrin, DDT, and anthracene were used in this study as probe compounds. Sorption of dieldrin and ?-endosulfan on Teflon lined centrifuge tubes (TLCT) and HPLC vials (HPLCV) was measured in methanol-water systems. Similarly, DDT and anthracene sorption on TLCT was also measured. The volume fraction of methanol (fc) ranged from 0.01to 1. The solution concentrations of 12C-dieldrin and 12C-?-endosulfan were analyzed using high pressure liquid chromatography (HPLC) with UV detection. Liquid scintillation counting (LSC) was used to measure solution concentrations of 14C-DDT and 14C-anthracene. The container sorption coefficients (KW) in aqueous systems were obtained by use of the Solvophobic model and extrapolating the sorption coefficient to zero fraction cosolvent (fc = 0). Using the Solvophobic model, the calculated percent recovery of ?-endosulfan due to sorption on TLCT and HPLCV in aqueous system was 30%. Dieldrin recovery at fc = 0 was 6 and 32% from HPLCV and TLCT, respectively. DDT adsorbed most on TLCT followed by dieldrin and least anthracene, with calculated recoveries in aqueous system of 29, 32, and 52%, respectively. Negligible adsorption was detected for dieldrin at fc ? 0.45 in TLCT and at fc ? 0.70 in HPLCV. Similarly negligible adsorption was detected for DDT and anthracene at fc ? 0.45 in TLCT. It is important to point out that most researchers assume that Teflon lined centrifuge tubes and HPLC vials do not adsorb organic chemicals. The sorption coefficients of dieldrin, DDT, and anthracene by 3 carbonatic soils, one organic soil, and one spodosol, were then determined in methanol-water systems that eliminated sorption on the TLCT and HPLCV. The soil sorption coefficients (KW) in aqueous systems were extrapolated at volume fraction methanol (fc = 0). The KW values were then normalized with soil organic carbon content (OC) to obtain KOC = KM/OC values. The KOC values for DDT, dieldrin, and anthracene obtained in this study were much lower than literature values and did not drastically vary across soil as it is reported in the literature. The KOC values for dieldrin obtained in this study varied within a factor of 2 compared to the literature factor of 4. For DDT, the KOC values varied within a factor of 4 compared to the reported literature factor of 13. The KOC data from this study strongly indicate that sorption on container walls if neglected is a potential source of error while determining adsorption of strongly hydrophobic chemicals in aqueous systems. It is therefore recommended that sorption experiments of strongly hydrophobic chemicals be carried out in TLCT above 45% cosolvent in a mixture with water and at and above 70% cosolvent in HPLC vials. The sorption coefficients in aqueous systems can then be calculated using the Solvophobic model eliminating errors due to sorption on container walls and over estimation of sorption coefficients. The hydrocarbonaceous surface area (HSA) of SHOCs calculated from sorption on TLCT, HPLCV, and by soils gave similar values as predicted by the Solvophobic theory.
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 Augustine Muwamba.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Nkedi-Kizza, Peter.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021819:00001


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DETERMINATION OF AQUEOUS SOIL SORPTION COEFFICIENT (Koc) OF
STRONGLY HYDROPHOBIC ORGANIC CHEMICALS (SHOCs) USING MIXED
SOLVENT SYSTEMS AND THE SOLVOPHOBIC MODEL




















By

AUGUSTINE MUWAMBA


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

2007

































2007 Augustine Muwamba



























To my Mom and Dad. Thanks go to them for their encouragement and interest in my education

since first grade.









ACKNOWLEDGMENT S

I would like to thank my advisor, Dr. Peter Nkedi-Kizza, for his guidance, encouragement,

support, and patience throughout this work. A lot of encouragement from him made this

research a success.

I would like to thank Dr. Roy D. Rhue and Dr. Jeffrey J. Keaffaber for all their technical

support, patience and advising me whenever I needed help.

Thanks also go to Dr. W. Harris, Dr. L.T. Ou and Dr. J. Thomas for allowing me to use

their laboratories.

Thanks go to the lab managers, Mr. K. Awuma and Mr. B. Querns for their technical

support throughout this work.









TABLE OF CONTENTS
page

A C K N O W L E D G M E N T S ......... ................. .................................................................................... 4

LIST OF TABLES ........................ .............................. ........ 7

LIST OF FIG U RE S ............. .. .. .......................... .......... ........ ......... .......... 8

A B ST R A C T ........... ................. .................................................................. 10

CHAPTER

1 IN T R O D U C T IO N ............................................................................................ .............. ....... 12

H y p oth e se s ................... ................... .............................3
Stu d y O bjectiv e s ......................................................................... 13

2 L IT E R A T U R E R E V IE W .................................................. ................................................... 16

Harmful Effects of Persistent Organic Pesticides (POPs) that are also (SHOCS) .................. 18
C o n c e p t o f K o c ............... .... ...... ..... .. .................. ............... ................................. 1 9
Variability of Koc Values in Literature for Persistent Organic Pollutants (POPs) that are
also (SH O C S ) .......................... .. ......... ... .. ...................................................2 3
T h e S o lv o ph ob ic T h eory ............................................................... ....................................... 2 4

3 M A TER IA L S AN D M ETH O D S .................................................................... .....................28

S o ils ............... .................... .................................................................. .. 2 8
S olv ents an d S orb ates ............................... ..... .... ......... ..................................................... 2 8
Teflon Lined Centrifuge Tubes, High Pressure Liquid Chromatography (HPLC) Glass
Vials, High Pressure Liquid Chromatography (HPLC), and Liquid Scintillation
C ou ntin g (L S C ) ...................................... ................................... ................. 2 9
Sorption Experim ents.. ......................... .............. ............... ..... .................................... 29
Reduced Sample Integrity Due to Sorption on container walls: ...................................... 29
Determination of Surface Areas of Teflon Lined Centrifuge Tubes and HPLC Glass
V ia ls ....................................................................... 3 0
T he Solv ophobic T h eory ............................ ... ............. ........ ............... ............... ... 30
Sorption of Persistent Organic Chemicals on Container Walls and Soils...................... 30
Sorption of p-endosulfan on teflon lined centrifuge tubes (TLCT) and HPLC
vials (H PL C V ) ..................................3...................... .......................... 32
Sorption of dieldrin on HPLC vials (HPLCV) .......................................................33
Sorption of dieldrin on teflon lined centrifuge tubes (TLCT)............................... 34
Sorption of anthracene on teflon lined centrifuge tubes (TLCT)............................. 34
Sorption of DDT on Teflon lined centrifuge tubes ..................................................35
Sorption Isoth erm s on S oils ......... ................................................................................... 36
Estimation of equilibrium concentrations .............................................................. 36
Sorption of anthracene on soils ................... ................. .................. 36









Sorption of DDT on soils...................................... ............. ............... 38
Sorption of dieldrin on soils ................................................. ........................... 39

4 R E SU LT S A N D D ISCU SSIO N ......... ............................ ................................... ......................45

Sorption on C ontainer W alls ......... .............. .. .............. ....... ............. ................. 45
Sorption of 12C-P-endosulfan on Teflon Lined Centrifuge Tubes (TLCT) and HPLC
V ials (H PL C V ) ....................................................................... ................ 45
Sorption of 12C-Dieldrin on Container W alls .............................................................. 46
Sorption on HPLC vials (HPLCV) and Teflon lined centrifuge tubes (TLCT).......46
Sorption of 14C-Anthracene on Teflon Lined Centrifuge Tubes (TLCT) .......................47
Sorption of 14C-DDT on Teflon Lined Centrifuge Tubes (TLCT)................................47
C o n clu sio n s ...................................................................... ............................... 4 8
Sorption Isotherm E xperim ents......... ................. ............................................................ 49
Sorption of D ieldrin on Soils ......... ................. ........................................................ 49
Sorption of A nthracene on Soils......... ................. .................................... ............... 50
Sorption of D D T on Soils.. ....................................................... ......................................... 52
C o n clu sio n s ......... ............. ......... ...................... .............................. 53

5 C O N C L U SIO N S ......... .. ........... ..................................... ............................................. 70

L IST O F R E FE R E N C E S ......... ................. ..................................................................................72

B IO G R A PH IC A L SK E T C H ......... .. ............ ................................................. .................. .. 76




























6









LIST OF TABLES


Table page

2-2 Sw, Kow and Koc values from the literature for selected POPs..........................................25

2-3 Comparison of measured and calculated Koc values in four soils.................................26

3-1 C characteristics of the soils used .................................................. ............. ............... 41

3-2 Some properties of the solvents (at 250C) used ............. ............................................41

3-3 Summary of initial and equilibrium concentrations used for sorption isotherms .............41

4-1 Parameters used to calculate chemical properties (HSA, Koc, and KM) ............................54

4-2 Sorption of DDT, 3-endosulfan, Anthracene and Dieldrin on containers. ........................ 54

4-3 Sorption coefficients (Kw and Koc), cosolvency powers (dc) and hydrocarbonaceous
surface area (H SA ) for D ieldrin .......................................................................................... 55

4-4 Sorption coefficients (Kw and Koc), cosolvency powers (dc) and hydrocarbonaceous
surface areas (H SA ) for A nthracene .......................... .......... ......................... .. ............... 55

4-5 Sorption coefficients (Koc), cosolvency powers (o) and hydrocarbonaceous surface
area s (H S A ) for D D T .............................................................. ........................................ 5 5









LIST OF FIGURES


Figure page

2-1 DDT :(C14H9Cl15)1, 1'-(2, 2, 2-Trichloroethylidene) bis (4-chlorobenzene).....................27

2-2 Dieldrin:(C12H8C160)3,4,5,6,9,9-Hexachloro-la,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-
dim etanonapth[2,3 -b] oxirene. ............ ............... ................ ........................................ 27

2-3 0-endosulfan:6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2;4,3-
benzadioxahepin 3 -oxide. ......................................................... .................................... 27

2 -4 A nthracen e: C 14H 0 ......................................................... ................................................ 2 7

3-1 Sorption of a chemical up to HPLC analysis .......................................42

3-2 Sorption of a chemical up to LSC analysis ....................................... 42

3-3 Calculation of the area of HPLC vials covered by solution............. .........................43

3-4 Calculation of the area of Teflon Lined Centrifuge Tubes covered by solution ...............44

4-1 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of 3-Endosulfan by Teflon Lined Centrifuge Tubes and HPLC Vials .... 56

4-2 Percent recovery of 3-Endosulfan sorption on Teflon Lined Centrifuge Tubes and
HPLC Vials........... .. .............. ......... .............. 56

4-3 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of Dieldrin by Teflon Lined Centrifuge Tubes and HPLC Vials............. 57

4-4 Percent recovery of Dieldrin sorption on HPLC Vials........ ................................................ 57

4-5 Percent recovery of Dieldrin sorption on Teflon Lined centrifuge Tubes (TLCT) ..........58

4-6 Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (f) for
Dieldrin sorption by Teflon Lined Centrifuge Tubes and HPLC Vials ...........................58

4-7 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of Anthracene by Teflon Lined Centrifuge Tubes. ............................. 59

4-8 Percent recovery of Anthracene sorption on Teflon Lined centrifuge Tubes .................. 59

4-9 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of DDT by Teflon Lined Centrifuge Tubes...............................................60

4-10 Percent Recoveries of Dieldrin sorption on Teflon Lined Centrifuge Tubes................... 60









4-11 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption ofD ieldrin by soils............................................ ............................ 61

4-12 Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (f) for
D ieldrin sorption by soils ................................................................................... ..... .... 6 1

4-13 D ieldrin K oc from different soils ................................................... ................................ 62

4-14 Relationship between the sorption coefficient (Kw) and soil organic carbon content
(O C) for sorption of D ieldrin by soils.......................................................... ............... 62

4-15 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of Anthracene by Krome soil. ............. ..............................................63

4-16 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of Anthracene by soils ........ ................ ........................... ............. .. 64

4-17 Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (f) for
Anthracene sorption by soils. ......... ............ ........................................... ............... 65

4-18 Anthracene Koc values from different soils ............................................. ................... 66

4-19 Relationship between the sorption coefficient (Kw) and soil organic carbon content
(O C) for sorption of A nthracene by soils ..................................... ........................ ......... 66

4-20 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of DDT by Krome soil. ............... ....................................... 67

4-21 Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of DDT by soils. ................................................67

4-22 Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (f) for
D D T sorption by soils. ........... .......... ..... ........................................... ................................6 8

4-23 DD T Koc values from different soils........................................... ............................. 68

4-24 Relationship between the sorption coefficient (Kw) and soil organic carbon content
(O C) for sorption of D D T by soils .................... .... ......... ....................... ............... 69









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

DETERMINATION OF AQUEOUS SOIL SORPTION COEFFICIENT (Koc) OF
STRONGLY HYDROPHOBIC ORGANIC CHEMICALS (SHOCs) USING MIXED
SOLVENT SYSTEMS AND THE SOLVOPHOBIC MODEL

By

Augustine Muwamba

December 2007

Chair: Prof Peter Nkedi-Kizza
Major: Soil and Water Science

Determination of the sorption coefficients (Koc) of strongly hydrophobic organic

chemicals (SHOCs) in aqueous systems is difficult due to their very low solubility and the

potential to adsorb on container walls and vessels. P-endosulfan, dieldrin, DDT, and anthracene

were used in this study as probe compounds. Sorption of dieldrin and P-endosulfan on Teflon

lined centrifuge tubes (TLCT) and HPLC vials (HPLCV) was measured in methanol-water

systems. Similarly, DDT and anthracene sorption on TLCT was also measured. The volume

fraction of methanol (f) ranged from 0.Olto 1. The solution concentrations of 12C-dieldrin and

12C-P-endosulfan were analyzed using high pressure liquid chromatography (HPLC) with UV

detection. Liquid scintillation counting (LSC) was used to measure solution concentrations of

14C-DDT and 14C-anthracene.

The container sorption coefficients (Kw) in aqueous systems were obtained by use of the

Solvophobic model and extrapolating the sorption coefficient to zero fraction cosolvent (f = 0).

Using the Solvophobic model, the calculated percent recovery of P-endosulfan due to sorption on

TLCT and HPLCV in aqueous system was 30%. Dieldrin recovery at f = 0 was 6 and 32% from

HPLCV and TLCT, respectively. DDT adsorbed most on TLCT followed by dieldrin and least









anthracene, with calculated recoveries in aqueous system of 29, 32, and 52%, respectively.

Negligible adsorption was detected for dieldrin at f > 0.45 in TLCT and at f > 0.70 in HPLCV.

Similarly negligible adsorption was detected for DDT and anthracene at f > 0.45 in TLCT. It is

important to point out that most researchers assume that Teflon lined centrifuge tubes and HPLC

vials do not adsorb organic chemicals

The sorption coefficients of dieldrin, DDT, and anthracene by 3 carbonatic soils, one

organic soil, and one spodosol, were then determined in methanol-water systems that eliminated

sorption on the TLCT and HPLCV. The soil sorption coefficients (Kw) in aqueous systems were

extrapolated at volume fraction methanol (f = 0). The Kw values were then normalized with soil

organic carbon content (OC) to obtain [Koc = KM/OC] values. The Koc values for DDT, dieldrin,

and anthracene obtained in this study were much lower than literature values and did not

drastically vary across soil as it is reported in the literature. The Koc values for dieldrin obtained

in this study varied within a factor of 2 compared to the literature factor of 4. For DDT, the Koc

values varied within a factor of 4 compared to the reported literature factor of 13. The Koc data

from this study strongly indicate that sorption on container walls if neglected is a potential

source of error while determining adsorption of strongly hydrophobic chemicals in aqueous

systems. It is therefore recommended that sorption experiments of strongly hydrophobic

chemicals be carried out in TLCT above 45% cosolvent in a mixture with water and at and above

70% cosolvent in HPLC vials. The sorption coefficients in aqueous systems can then be

calculated using the Solvophobic model eliminating errors due to sorption on container walls and

over estimation of sorption coefficients.

The hydrocarbonaceous surface area (HSA) of SHOCs calculated from sorption on

TLCT, HPLCV, and by soils gave similar values as predicted by the Solvophobic theory.









CHAPTER 1
INTRODUCTION

Experimental determination of soil sorption coefficients (Koc) values of strongly

hydrophobic organic chemicals (SHOCs) has been traditionally done in aqueous systems

assuming that there is no sorption on container walls and vessels. This might have led to a lot of

variability in literature data reported on Koc of strongly hydrophobic organic chemicals.

Although there are other losses through evaporation of volatile compounds(physical processes),

photolysis, oxidation, reduction and completing (chemical reactions) and biodegradation

(Namiesnik et al., 2002; Namiesnik et al., 2000), adsorption of these chemicals on container

walls plays a significant role in variability of literature Koc values (Lung et al., 2000)

Strongly hydrophobic organic chemicals have low water solubility (Sw) of less than 10-5

mol/L, have log Kow values > 5-6 (Pontolillo and Eganhouse, 2001) and log Koc values > 4

(Karichkoff, 1981). More than 700 publications from 1944 to 2001 for DDT and DDE, aqueous

solubility and Kow values revealed a variation of up to 4 orders of magnitude (Pontolillo and

Eganhouse, 2001). This variability in the literature has been observed also for other persistent

organic pollutants (POPs), (Table2-2).

Based on The Stockholm Convention (2002), 9 of the 12 persistent organic pollutants are

pesticides (Table 1-1). These pesticides can also be classified as SHOCs. POPs are typically

water hating and fat loving chemicals (i.e. hydrophobic and lipophilic) and are persistent in the

environment having long half lives in soils, sediments, air or biota. In soil/sediment, a POP could

have a half life of years or decades and several days in the atmosphere (Jones et al., 1999). POPs

have become ubiquitous in nature.

Use of Solvophobic theory has helped in prediction of sorption of hydrophobic organic

compounds by soils and sediments. The model stipulates that the sorption of neutral hydrophobic









organic chemicals decreases exponentially as the cosolvent fraction increases (Rao et al., 1985).

Extrapolating sorption coefficient at zero cosolvent in mixed solvents determines sorption of

strongly hydrophobic organic pesticides in aqueous systems (Nkedi-Kizza et al., 1985).

A range of volume fraction of methanol (f) in water where there was no sorption of

anthracene, DDT, P-endosulfan, and dieldrin on Teflon lined centrifuge tubes (TLCT) and HPLC

vials was determined. Above that range of methanol, sorption coefficients (Koc) of anthracene,

dieldrin and DDT were determined using five soil series (Chekika, Perrine, Krome, Monteocha,

and Lauderhill). Anthracene was used as a reference compound because it has no functional

groups and its total surface area (TSA) is equal to the hydro carbonaceous surface area (HSA).

Dieldrin and DDT are among the strongly hydrophobic organic pesticides (SHOPs) and are also

POPs (The Stockholm Convention, 2001). 3-endosulfan is a strongly hydrophobic organic

pesticide that has been detected in canals in South Dade County, Florida (Zhough et al., 2003).

Hypotheses

1. Strongly hydrophobic organic chemicals (SHOCs) adsorb on container walls and
vessels during determination of Koc values in aqueous systems.

2. Mixed solvent systems can eliminate sorption of strongly hydrophobic organic
chemicals on container walls and vessels.

3. The Solvophobic model can be used to calculate aqueous Koc of strongly
hydrophobic organic chemicals by using sorption coefficients measured in mixed
solvent systems where there is no sorption on container walls.

4. Sorption data of SHOCs on container walls and by soils can be used to calculate
the hydrocarbonaceous surface area (HSA) of SHOCs.



Study Objectives

1. Determine the range of mixed solvents (water plus methanol) in which
sorption on container walls is eliminated for selected strongly hydrophobic
chemicals (SHOCS) that include persistent organic pollutants (POPs).









2. Measure sorption coefficients (KM) values in mixed solvents for SHOCs
and extrapolate the sorption coefficients (Kw) in aqueous systems using the
Solvophobic model. Normalize Kw values with soil organic carbon content (OC)
to calculate [Koc = Kw/OC] values of selected SHOCs.

3. Compare Koc values obtained in this study to literature values for various
SHOCS used in this research.









Table 1-1. The dirty dozen: Persistent Organic Pollutants (POPs)
Pesticides Aldrin, DDT, Dieldrin, Endrin, Heptachlor, Hexachlorobenzene,
Chlordan, Mirex, Toxaphene
Industrial chemical Polychlorinated biphenyls(PCBs)
by products Poly chlorinated dibenzo-p-dioxins(Dioxins) and Furans
The Stockholm Convention (2001)









CHAPTER 2
LITERATURE REVIEW

Variability in literature data for aqueous sorption coefficients (Koc) of strongly

hydrophobic organic pesticides (Table2-2) can partly be attributed to losses (source of error) that

occur while conducting experiments for Koc determination and partly to variability

(Karapanagioti et al., 2000) in the source and nature of soil organic matter. Losses occur through;

adsorption of chemicals on the walls of samplers and vessels, evaporation of volatile compounds

(physical processes), photolysis, oxidation, reduction and complexing(chemical reactions) and

biodegradation (Namiesnik et al., 2002, Namiesnik et al., 2000). Sorption on container walls

plays a significant role in variability of Koc literature data (Manoli et al., 1999, Baltussen et al.,

1998).

Several researchers have shown that 40-80% of the poly chlorinated biphenyls (PCBs) in a

sample may be adsorbed on to the poly tetrafluoroethylene (PTFE) surface (Baltussen et al.,

1999, Lung et al., 2000). Glass containers may be responsible for a 10-25% drop in water sample

content of polychlorinated biphenyls (PCBs) and poly aromatic hydrocarbons (PAHs) causing

drops in analyte concentration (Manoli et al., 1999, Baltussen et al., 1998).

Nine of the 12 chemicals which belong to the class of most hazardous environmental

pollutants enlisted as persistent organic pollutants (POPs) under the Stockholm Convention

(2001) are pesticides. These POPs are also strongly hydrophobic organic chemicals (SHOCs).

POPs are typically water hating and fat loving chemicals (i.e. hydrophobic and lipophilic) and

are persistent in the environment having long half lives in soils, sediments, air or biota. In

soil/sediment, a POP could have a half life of years or decades and several days in the

atmosphere (Jones et al., 1999).









According to Webster et al. (1998), persistence in the environment is defined operationally

from a model calculated overall residence time at steady state in a multimedia environment. In

aquatic systems and soils, POPs partition strongly to solids, mainly organic matter, avoiding

aqueous phase. They also partition in to lipids in organisms rather than entering the aqueous

milieu of cells and become stored in fatty tissue. This leads to their accumulation in food chains

since their metabolism in biota is slow. POPs have a potential to enter the atmosphere through

volatilization from soils, vegetation and water because of their resistance to breakdown reactions

in air, they travel long distances before being redeposited (Ritter et al., 1995). Repeated

volatilization and deposition leads to their accumulation in areas far removed from where they

were used or emitted.

An important class of persistent organic pesticide is the organo chlorine pesticides like

DDT, aldrin, endrin, dieldrin, hexachlorobenzene, heptachlor, mirex, chlorodane and toxaphene

(Table 1-1). Some POPs are accidental byproducts of combustion or the industrial synthesis of

other chemicals for example polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (Dioxins),

chlorinated paraffins, and dibenzo- p- furans (Furans), (Ritter et al., 1995).

The properties of unusual persistence and semi-volatility, coupled with other

characteristics, have resulted in the presence of compounds such as PCBs all over the world,

even in regions where they have never been used. They have become ubiquitous in nature. They

have been measured on every continent, at sites representing every major climatic zone and

geographic sector throughout the world (Ritter et al., 1995). These include remote regions such

as the open oceans, the deserts, the arctic and the Antarctic, where no significant local sources

exist and the only reasonable explanation for their presence is long-range transport from other

parts of the globe. Some POPs have been reported in air, in all areas of the world, at









concentrations up to 15ng/m3; in industrialized areas, concentrations may be several orders of

magnitude greater. POPs have also been reported in rain and snow (Ritter et al., 1995)

Properties of DDT (Fig. 2-1), dieldrin (Fig. 2-2), 3-endosulfan (Figure 2-3) and anthracene

(Fig. 2-4) are shown in table 2-1.

Anthracene was used to show the validity of Solvophobic model. It served as an ideal

sorbate for evaluating the Solvophobic theory because its sorption is characterized by

Solvophobic interactions (hydro carbonaceous surface area (HSA) is equal to total surface area

(TSA-202 A2).

Harmful Effects of Persistent Organic Pesticides (POPs) that are also (SHOCS)

The concern of POPs concentrates around their impact on top predator species, humans

inclusive. Clear evidence of their effects is in birds and marine mammals. In great lakes (Giesy et

al., 1994) and in Europe (Bosveld and Van den Berg, 1994), numerous subtle but far reaching

effects on the reproductive potential of fish eating birds are reported. POP residues have

increased in some top predators for instance harbor seals in the Southeast North Sea (Reijnders et

al., 1997), white- tailed eagles in the Baltic and piscivorous birds in the great lakes (Munro et al.,

1994).

POPs, principally PCBs, have also been reported to cause reproductive impairment and

this has been shown in seals in the Baltic sea (Bergman and Olsson, 1985) and the Dutch

Wadden Sea (Reijnders, 1986) and in beluga whales in the St. Lawrence sea way, Canada

(Beland et al. 1993). In addition to being carcinogens, POPs are among the chemicals

responsible for sex hormone or endocrine disruption in humans and wild life (Harrison et al,

1995; Kavlock et al., 1996).

DDE a metabolic break down product of DDT affects egg shell thickness (thinning) in

birds of prey for example wild fowls (Ratcliffe, 1967 and 1970, Pearce et al., 1979). Man's









exposure to DDT lies in taking contaminated food including maternal milk. Long term exposure

leads to chronic illness and breast cancer risk. Toxicity of DDT spreads to fish too. 50% of initial

amounts of DDT are found in soil, even 10-15 years after use (Smith, 1991).

Man is exposed to dieldrin through eating contaminated fish and shell fish. Infants are

exposed from breast milk. Dieldrin decreases the effectiveness of our immune system, cause

cancer, increase infant mortality, reduces reproductive success, causes birth defects and damages

the kidneys (Smith, 1991). Harmful effects of p-endosulfan are not cleary understood however

excess levels of endosulfan are toxic to both humans and animals (Smith, 1991).

Concept of Koc

The soil sorption coefficient (Koc) is the ratio between the concentrations of a given

chemical sorbed by the soil and that dissolved in the soil water normalized to the total organic

carbon content of the soil. It is used to quantify soil sorption and the advantage of this is that Koc

for a particular pesticide is assumed to be independent of the soil pesticide combination (Nkedi-

Kizza et al., 1983, Rao and Davidson 1980). Sorption is among the major processes that affect

the fate of pesticides in the soil environment. It also regulates the rates and magnitudes of other

processes that govern the fate and transport of organic contaminants in soils and sediments.

Sorption of pesticides decreases their biological activities and rates of biological degradation.

However, due to surface catalyzed hydrolysis, sorption may enhance non biological degradation

(Stevenson, 1994).

Adsorption of hydrophobic organic pollutants by soil is strongly dependent on the soil

organic matter content (Means et al., 1980; Xing et al., 1994). Organic matter can be humic or

nonhumic (Morrill et al., 1982) and humified material is often a stronger sorbent for non-ionic

pesticides due to the presence of oxygen -containing functional groups like -COOH, phenolic,

aliphatic, enolic, -OH, and C=O. However this is not true for ionic pesticides, due to the range









of possible sorption mechanisms (Hance, 1988). The chemistry of soil organic matter in soils

from different geographical regions varies. Soil organic matter may vary from soil to soil in its

polarity, elemental composition, aromaticity, condensation, and degree of diagenetic evolution

from a loose polymer to condensed coal-like structures (Garbarini and Lion, 1986; Gauthier et

al., 1987; Grathwohl, 1990; Karapanagioti et al., 2000). Therefore land variations, such as type

and age of soil organic matter may affect sorption of non-ionic pesticides.

Three different processes; film diffusion, retarded intra particle diffusion and intrasorbent

diffusion, that involve diffusion mass transfer cause sorption related nonequilibrium. Retarded

intraparticle diffusion is aqueous phase diffusion of solute within pores of micro porous

particles; forexample, sand grains mediated by retardation resulting from instantaneous sorption

to pore walls. Intra sorbent (intra organic matter) diffusion involves the diffusive mass transfer of

sorbate with in the matrix of the sorbent. It involves diffusion within organic matter matrix. The

major assumption in intra organic matter diffusion model is that sorbet organic matter is a

polymeric type substance within which sorbate can diffuse. The organic matter associated with

natural sorbents is reported to be a flexible, cross-linked, branched, amorphous (noncrystalline),

polyelectrolytic polymeric substance (Brusseau et al., 1991).

The amount of chemical adsorbed is a function of both the soil and the solute. The

distribution coefficient or partition coefficient, Kw (L/kg), is estimated by Kw = fo, Koc, where

foe is a function of the soil and is the fraction of naturally occurring organic carbon measured in

the soil and Kw is a function of the solute and is the partition coefficient of the solute between

water and organic carbon.

A linear model of the following form is employed to approximate sorption data for soils

and sediments.









Se = KwCe 2-1

Where Se (mg/kg) is the mass of solute sorbed per unit mass of solid at equilibrium, Ce

(mg/L) is solute concentration and Kw (L/kg) is the distribution coefficient in aqueous systems.

The parameter, octanol-water partitioning coefficient (Kow) which is the measure of

hydrophobicity (water repulsing) of an organic compound solutee) is given by:

Kow = Co/Cw 2-2

Where Co (mg/L) is the concentration in the octanol phase and Cw (mg/L) is the concentration in

aqueous phase. Kow is used in assessment of environmental fate and transport for organic

chemicals because the octanol phase is a surrogate for the lipid phase or organic carbon content

of environmental compartments. Kow is correlated to water solubility, soil/sediment adsorption

coefficients, and bioconcentration factors for aquatic life (Lyman et al., 1990) and this makes it a

key variable in estimation of these variables. The less hydrophobic (small Kow) a compound is,

the more soluble it is in water and less likely it will adsorb to soil particles (Bedient, 1994).

Several relations have been developed between Koc and Kow:

Log Koc = a log Kow + b 2-3

Values reported for a and b in Eq. 2-3 include (a = 1 and b = 0.48) for polycyclic aromatic

hydrocarbons, (a = 0.52 and b = 4.4) for certain group of pesticides and (a = 0.72 and b = 3.2) for

alkylated and chlorinated benzenes (Jones and de Voogt, 1999). Conclusion from the available

data is that, values of a and b are determined by the type of compounds that is compound classes

and range of liphophilicity on which the relationship is established and only to a smaller degree

by the type of natural sorbents used (Jones and de Voogt, 1999).

According to Karickhoff et al. (1981), the following relationship was found;

Log Koc = 0.989 log Kow -0.346 (5PAHs, r2 = 0.997) 2-4









Equation 5 was for 13 methylated and halogenated benzenes (Schwarzenbach and

Westall, 1981)

Log Koc = 0.72 log Kow + 0.49 (r2=0.95) 2-5

Vowles and Matoura (1987) proposed that different classes of solutes don't have similar

affinities for octanol and natural organic matter. After arranging hydrocarbons into homologous

groups, they came up with the following relation ships:

Log Koc = 0.774 log Kow + 0.37 (alkylnaphthalenes, r2=0.992) 2-6

Log Koc = 1.20 log Kow 1.13 (4 PAHs, r2 = 0.998) 2-7

Log Koc = 0.904 log Kow -0.46(alkyl benzenes, r2 = 0.992) 2-8

Chiou (1990) reported a relationship between KOM and Kow for sorption of various organic

compounds, including several pesticides, by different soils and sediments as;

Log KOM = 0.94 log Kow-0.779 (r2=0.989) 2-9

Where KOM is the partition coefficient for the organic compound between soil organic

phase (based on organic matter) and water.

There are propositions that solubility relationships for aliphatic and aromatic solutes are

different because of their dependence on solute's polarizability and basicity (Kamlet et al.,1987)

and additions of ring fragments and functional groups on the aromatic ring (Karickhoff,1985).

Experimental determination of Koc values is difficult, costly and time consuming. For

compounds of low solubility such as DDT, lindane, and PCB's, Koc values are inaccurate

(Chiou et al., 1979; Kenaga and Goring, 1980). Therefore, correlations between Koc and Kow

listed in Eqs. 2-3 to 2-9 might be questionable due to experimental errors made when measuring

Koc values in aqueous systems for strongly hydrophobic organic chemicals (SHOCs).









Variability of Koc Values in Literature for Persistent Organic Pollutants (POPs) that are
also (SHOCS)

Recently research scientists have questioned the reliability of chemical property data in the

literature especially for SHOCs (Pontolillo and Eganhouse, 2001). Since this class of chemicals

is sparingly soluble in water, direct determination of Sw, Kow and Koc is problematic. Therefore

indirect estimation based on correlations between Sw, Kow or Koc with measurable molecular

parameters (connectivity indices, HPLC capacity factors etc) have been used in the literature

(Sangster, 1997, Karichkoff, 1981). However, these techniques depend on various assumptions

that produce results that are not always comparable ((Pontolillo and Eganhouse, 2001). A

literature search from 700 publications from 1944 to 2001 for DDT and DDE, Sw and Kow

values revealed a variation of up to 4 orders of magnitude (Pontolillo and Eganhouse, 2001).

This trend in parameter variability in the literature is true for other POPs (Table 2-2).

Environmental risk assessment, fate and transport models, and sediment quality guidelines

may not be accurate because of the variability of basic data needed to predict the fate of

contaminants (POPs) in the environment (Renner, 2002). This problem is clearly demonstrated in

Table 2-1. For example the Koc values for dieldrin vary within a factor of 4 and for DDT the

Koc values vary within a factor of 13. Karichkoff (1981) reported Koc values for weakly

hydrophobic chemicals (Koc < 1000) to vary within a factor of 2. The variation in the literature

values of the three parameters (Kow, Koc, and Sw) for SHOCs has been attributed to

measurement uncertainty due to different analytical methods, temperature differences, lack of

equilibrium and impurities of test compounds (Linkov et al., 2005; Chiou et al., 2005). However,

one process that damages sample integrity before analysis is analyte adsorption onto the walls of

samplers and vessels. This process has been ignored in the literature especially for SHOCs.

Wolska et al. (2005) reported up to 70% of adsorption of PAHs and PCBs on walls of containers.









The adsorption on walls of containers increased as log Kow of the chemicals increased from 6.5

to 8.5.

The Solvophobic Theory

Rao et al., (1985) and Nkedi-Kizza et al., (1985) showed that the Solvophobic model can

be used to estimate (in aqueous systems) the sorption coefficient normalized to soil organic

carbon content (Koc) of hydrophobic organic chemicals. Nkedi-kizza et al., (1985) suggested

that sorption of SHOCs in aqueous systems can be determined in mixed solvents by

extrapolating Koc at zero co-solvent. Data for one SHOC (Anthracene) and two pesticides

(Atrazine and Diuron) were presented that showed the validity of the Solvophobic model (Table

2-3).









Table 2-1. Properties of the chemicals used in the study
Property Chemical
DDT Dieldrin
Melting point(oC) 108.5 175-176


Aqueous solubility at
25C([tg/L)
Log Koc
Boiling point(C)

Appearance
Source: Nkedi-Kizza et al.,


1.2-5
5.15 6.26
260

White powder
1985; Kidd et al.,


140
4.08-4.55
385

White crystals
1991.


P-endosulfan
70-100

320
4.06
106
Colorless
crystals


Anthracene
217

75
4.22
340
Yellow
cryastals


Sw, Kow and Koc values from the literature for selected POPs
*Log Kow Kow
5.17 to 7.40 147,910 to 25,118,864
4.89 to 6.91 77,624 to 8,128,305
3.69 to 6.20 4,897 to 1,584,893
3.03 to 6.42 1,071 to 2,630,267


*Log Koc
2.61 to 4.69
4.58 to 5.57
5.14 to 6.26
4.08 to 4.55
2.56 to 4.56


Source
a
a and b
a
a


Koc
407 to 48,978
38,019 to 371,535
138,038 to 1,819,701
12,023 to 35,481
363 to 36,308


*Sw (gg/L) Temperature (C)
17 to 180 25
1.2 to 5.5 25
220 to 260 25
Ritter et al., 1995; b. Pontolillo and Eganhouse, 2001.


Table 2-2.
Pesticide
Aldrin
DDT
Dieldrin
HCB

Pesticide
Aldrin
Chlordane
DDT
Dieldrin
HCB


Pesticide
Aldrin
DDT
Endrin
Source: a.









Table 2-3. Comparison of measured and calculated KOC values in four soils
Measured Koc in Measured Koc in
methanol-water. acetone-water.
Measured Koc Calculated with Calculated with
Sorbate Literature Koc in water (f =0) Solvophobic model Solvophobic model
Anthracene 15849 16032 16560 16912
Atrazine 146 96 90 89
Diuron 426 426 417 351


Source:


Nkedi-Kizza


1985



















Figure2-1.DDT :(C14H9C115)1, 1'-(2, 2, 2-Trichloroethylidene) bis (4-chlorobenzene)

Cl
CC
CI
CI




CI CI


Figure2-2.Dieldrin:(C12H8C160)3,4,5,6,9,9-Hexachloro- a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-
dimetanonapth[2,3-b] oxirene.


CI
\/CI
CCC







0 0


Figure2-3.P-endosulfan:6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2;4,3-
benzadioxahepin 3-oxide.


Figure 2-4. Anthracene: C14Hio









CHAPTER 3
MATERIALS AND METHODS

Soils

Five soils were used of which three were carbonatic (Perrine, Chekika and Krome) and two

non carbonatic (Lauderhill, organic) and (Monteocha, Spodosol). The soils were taken from 0-15

cm of top soil. The Spodosols were collected from Alachua County, Florida. Carbonatic soils are

defined as soils containing 40% carbonates (calcite and/or dolomite). The carbonatic soils in

South Florida are classified as Entisols and the associated organic soils (Histosols) are mainly

saprists and fibrists (NRCS, 1987). Organic soils are defined as soils containing a minimum of

12% organic carbon when the mineral portion contains no clay or 18 % organic carbon if the soil

has 60% or more clay (Lucas, 1982).The soils were selected to represent different geographical

conditions and organic matter content. The soil series are presented in Table 3-1. The organic

carbon content of the soils was determined by the dichromate method (Walkley and Black,

1934).

Solvents and Sorbates

The binary solvents used in this study were various mixtures of methanol and 0.01MCaCl2.

Methanol was chosen to represent an organic cosolvent that is completely miscible with water.

The properties of the solvents are shown in Tables 3-2.

Anthracene was selected to represent an ideal strongly hydrophobic organic chemical

(sorbate) without any polar functional groups. Its total surface area (TSA) is equal to

hydrocarbonaceous surface area (HSA). Radio-labeled 14C- anthracene was used as a tracer for

12C-anthracene. Dieldrin, 3-endosulfan, and DDT are strongly hydrophobic organic chemicals

(SHOCs). Radio-labeled 14C-DDT was used as a tracer for 12C-DDT. Dieldrin, B-endosulfan,









methanol, and water all of HPLC grade were obtained from Fisher Scientific. All chemicals

were of 99.9% purity.

Teflon Lined Centrifuge Tubes, High Pressure Liquid Chromatography (HPLC) Glass
Vials, High Pressure Liquid Chromatography (HPLC), and Liquid Scintillation Counting
(LSC)

Teflon lined centrifuge tubes are widely used in many experiments. They are made up of a

polymer called poly tetraflouroethylene (PTFE). The tubes were obtained from Fisher scientific.

Before samples are analyzed by HPLC-UV, they are first put in HPLC vials and then put in

autosampler for injection. They are made up ofborosilicate (glass). The vials were bought from

Fisher scientific. The HPLC system consisted of a pump: SP8800, an Intergrator: Dionex4270,

Detector: Waters 490 programmable multivalent detector, and Autosampler: SP8780. Column:

Nova-Pak C18.

The Liquid scintillation counter (Beckman LS 100-C model) was used to determine the 14C

activity in 1-mL aliquots of solutions added to (Scinti-Verse II scintillation liquid, Fisher

Scientific).

Sorption Experiments

Before conducting sorption experiments, the following were put in to consideration.

Reduced Sample Integrity Due to Sorption on container walls:

The three possible steps where a chemical is sorbed before HPLC analysis when working

in aqueous systems are:

1. Preparation of a stock solution in containers

2. Transfer of solution with plastic pipette to centrifuge tubes

3. Transfer of solution with plastic pipette to HPLC vials after centrifugation.

These three steps are illustrated in Fig. 3-1.









These sources of errors also occur when using LSC (Fig. 3 -2). Unlike in HPLC analysis

where some of its parts can sorb the chemical, LSC parts are excluded in the LSC analysis. The

solution sample to be analyzed is directly added to the scintillation liquid which is a mixture of

organic solvents. The possible error is due to the pipette used to transfer the solution.

All the stock solutions of the chemicals that were used in this research were prepared in

pure methanol to eliminate sorption on the containers. Pipette tips were first rinsed with 1- mL

methanol before being used in any step of the procedure. For the LSC analysis, after the sample

had been transferred into the scintillation vial the pipette was rinsed with 1 -mL of the

scintillation liquid and then added to the scintillation vial.

Determination of Surface Areas of Teflon Lined Centrifuge Tubes and HPLC Glass Vials

Since ImL of solution was added to square flat bottom HPLC vials when analyzing

solutions from sorption experiments, the area of the HPLC vials covered by the solution was

calculated. It was calculated to be 4.76 cm2 using the dimensions of the vial (Fig. 3 -3).

The area of the Teflon Lined Centrifuge tube covered by the solution was calculated by a

scanning model (Rhinoceros 3D SR410, 2006). The area of the tube covered by 10 mL of the

solution was calculated to be 38.5 cm2 (Fig. 3-4).

The Solvophobic Theory

Solvophobic theory was used to carry out the following;

Sorption of Persistent Organic Chemicals on Container Walls and Soils

During batch sorption experiments the main processes that would damage sample integrity

would include sorbate adsorption on the walls of samplers, vessels, tubing, components of the

pump, and injector valves; chemical reactions (photolysis, oxidation, reduction, and completing)

and biodegradation. To reduce sorbate loss before analysis, steps were taken to analyze the

samples quickly. Also working in mixed solvents would reduce sorption on container walls. In









mixed-solvents, biological degradation is also reduced due to microbial toxicity of the organic

solvents.

For sorption of SHOCs on container walls, the following equations were developed based

on the Solvophobic model in Eq. 3-1 (Rao et al., 1985; Nkedi-Kizza et al., 1985)

KM = K exp (-ad"of) 3-1
RM = Ce/Co 3-2

Se = V/A (C -Ce) 3-3

KM = Se/Ce = V/A (Co/Ce-1) 3-4

KM= V/A(1/RM-1); Kw= V/A(1/Rw-1) 3-5

RM= 1/ (1 + (A/V) Kw exp (- adof) 3-6

Rw= 1/(1+ (A/V) KW) 3-7

Where KM and Kw are sorption coefficients (mL/cm2) in co-solvent and in aqueous

systems, respectively; RM= fraction of chemical recovered at each ft; Ce = equilibrium solution

concentration ([tg/mL); Co = initial solution concentration ([tg/mL); Se = adsorbed concentration

(ag/cm2); V = volume of solution added to the tube (mL); A (cm2) = area of the tube covered by

volume V; Rw and RM = fraction of chemical recovered in water and mixed solvents,

respectively. Equation 3-1 can be used to calculate Kw at f = 0 and Eq. 3-6 to calculate Rw also

atf = 0.

The sorption on container walls was carried out as one-point isotherm in triplicate.

The value of ao in Eqs. 3-1 and 3-6 is the cosolvency power and can also be equated to the

hypothetical liquid-liquid partition coefficient. Therefore it may be approximated as:

c = In [SC/Sw] 3-8

Where Sc and Sw are the hydrophobic chemical mole fraction solubility in neat cosolvent

and water, respectively. The value of ac is strongly correlated to solute properties such as









octanol-water partition coefficient (Kow) and molecular hydrophobic surface area (HSA), and to

solvent properties such as dielectric constant, interfacial tension and bulk surface tension

(Yalkowsky et al., 1976)

ac = [AyHSA]/(kT) 3-9

AyC = wy- 7 (ergs/A2) = difference in interfacial free energy at the aqueous interface and the

organic co-solvent interface with the hydro carbonaceous surface area (HSA, A2) of SHOC

molecule; k (ergs/K) is Boltzmann constant; T is temperature in K.

For sorption of SHOCs on soils Eqs.3-3 and 3-4 are modified as follows:

KM = Se/Ce = V/m (Co/Ce-1) in mixed solvents 3-10

Kw = Se/Ce = V/m (Co/Ce-1) in water 3-11

Where KM and Kw are sorption coefficients (L/kg) in co-solvent and in aqueous systems,

respectively; m = mass of soil (kg). Other parameters have been defined earlier. Kw can be

estimated at f = 0 using Eq. 3-1 and KM data obtained in the range of co-solvent, where sorption

on container walls is eliminated.

Sorption of P-endosulfan on teflon lined centrifuge tubes (TLCT) and HPLC vials
(HPLCV)

Appropriate volumes of 11 g/mL solution of P-endosulfan were added to 50 mL Teflon

lined centrifuge tubes and volumes of 0.01M CaC12 solutions were added to make a total of 10

mL thus obtaining fractions of methanol (f) increasing from 0.1 to 0.8. The range of maximum

equilibrium concentration (Ce) at each f was predetermined to be the same by varying the

amount of Co added to make the 10 mL of solution. Each co-solvent was prepared in triplicates.

The solutions were sampled after 24 hours without shaking (batch method). A sub-sample (1

mL) of each triplicate was put in HPLC vials. The solutions were analyzed by high pressure

liquid chromatography (HPLC) with UV detection. All the standards were prepared in methanol.









The conditions for HPLC were: mobile phase, 80%acetonitrile: 20%water, wavelength, 214 nm,

and flow rate of 1 mL/minute. For 3-endosulfan sorption on container walls was not separately

determined for TLCT and HPLC vials. The measured concentration of the aliquot was

designated as Ce (ag/mL). The Ce values at each f were then used to calculate RM and KM using

Eqs. 2-2 and 2-4, respectively. However, the area of the TLCT covered by 10 mL was used in

Eq.3- 4. Equations 3-1 to 3-6 and 3-9 were used to calculate properties of P-endosulfan

(cosolvency power, percent of a chemical recovered from the HPLC vials plus TLCT, sorption

coefficient in water, and HSA). The ratio of V/A was essentially equal for TLCT and HPLCV.

Sorption of dieldrin on HPLC vials (HPLCV)

Appropriate volumes of dieldrin initial concentrations of 2.5, 3.5, 4, 5, 6 and 7([tg/mL)

were added to 0.01 M CaC12 solution in HPLC vials to make up 1 mL of solution yielding 0.25,

0.35, 0.4, and 0.5 fractions of methanol (f). The range of equilibrium concentration (Ce) at each

f was predetermined to be the same by varying the amount of Co added to make the 10 mL of

solution .Each cosolvent was used in triplicates. HPLC-vials of each cosolvent were prepared in

triplicates. The 1 mL solution of each cosolvent was left to stand for 24 hours. Equilibrium

concentration was analyzed using HPLC-UV. Conditions of the HPLC were; mobile phase of

80% methanol and 20% water, wavelength of 220 nm, sensitivity of 0.04 Aufs and flow rate of

1.5 mL/min, and C-18 column. All the standards were prepared in methanol. Samples were

injected thrice in the HPLC system. Percent recoveries(R) were computed by dividing

equilibrium concentration (Ce) by original concentration (Co) then multiplying by hundred (R=

(Ce/Co)*100). The area covered with solution in HPLC vials was calculated from the vial

dimensions and it was found to be 4.76 cm2. Equations 3-1 to 3-6 and 3-9 were used to calculate

properties of Dieldrin (cosolvency power, percent of a chemical recovered from the HPLC vials,

sorption coefficient in water, and HSA).









Sorption of dieldrin on teflon lined centrifuge tubes (TLCT)

Initial concentration (Co = 2 [Lg/mL), was mixed with 0.01M CaC12 solutions in a Teflon

lined centrifuge tubes to make a total of 10 mL that yielded 0.10, 0.20, 0.25 and 0.30 fractions of

methanol (f). The range of equilibrium concentration (Ce) at each f was predetermined to be the

same by varying the amount of Co added to make the 10 mL of solution. Centrifuge tubes of each

cosolvent were prepared in triplicates. The 10 mL solution of each cosolvent was left to stand for

24 hours. Equilibrium concentration was analyzed using HPLC-UV. Conditions of the HPLC

system were; wavelength of 220nm, sensitivity of 0.04Aufs, flow rate of 1.5mL/min; mobile

phase of 80%methanol and 20%water, and C-18 column. All the standards and the samples were

added to HPLC vials in methanol to make up 1 mL of at least 70% methanol. Samples were

injected thrice in the HPLC system. Concentrations that were below detection limit after dilution

of samples in HPLC vials with methanol were spiked with a known concentration of dieldrin in

pure methanol. The measured concentration of the aliquot was designated as Ce (tg/mL). The Ce

values at each f were then used to calculate RM and KM using Eqs. 3-2 and 3-4, respectively. The

area of the TLCT covered by 10 mL (A = 38.53 cm2) was used in Eq.3- 4. Equations 3-1 to 3-6

and 3-9 were used to calculate properties of dieldrin (cosolvency power, percent of a chemical

recovered from the TLCT, sorption coefficient in water, and HSA).

Sorption of anthracene on teflon lined centrifuge tubes (TLCT).

A volume of 12C-Anthracene of initial concentration of 0.1 [tg/mL in methanol and a

volume of 14C-Anthracene (10000 cpm/mL) also in methanol were pipetted into 50mL Teflon

lined centrifuge tubes. A volume of0.01M CaC12 was added to make a total of 10 mL that

resulted in 0.01, 0.06, 0.1, 0.20, 0.25 and 0.3 fractions of methanol. The range of equilibrium

concentration (Ce) at each f was predetermined to be the same by varying the amount of Co

added to make the 10 mL of solution. Each cosolvent was used in triplicates. The 10 mL solution









was left to stand for 24hours. After 24 hours, equilibrium concentration was obtained by

removing ImL of the supernatant from each cosolvent, put in a vial containing 5 mL of cocktail

(Scinti-Verse II scintillation solution) and analyzed using a Beckman LS 100-C liquid

scintillation counter (LSC). The analyzing time was 5 minutes. Back ground radioactivity from a

blank of methanol + calcium chloride solution was subtracted from each LSC counts of the

sample. Equations 3-1 to 3-6 and 3-9 were used to calculate properties of Anthracene

(cosolvency power, percent of a chemical recovered from the Teflon lined centrifuge tubes,

sorption coefficient in water, and HSA).

Sorption of DDT on Teflon lined centrifuge tubes

A volume of 12C-DDT of initial concentration of 0.01 [tg/mL in methanol and a volume of

14C-DDT (10000 cpm/mL) also in methanol were pipetted into 50mL Teflon lined centrifuge

tubes. A volume of0.01M CaC12 was added to make a total of 10 mL that resulted in 0.1, 0.2, 0.3

and 0.4 methanol fractions. The range of equilibrium concentration (Ce) at each ft was

predetermined to be the same by varying the amount of Co added to make the 10 mL of solution.

Each cosolvent was used in triplicates. The 10 mL solution was left to stand for 24hours. After

24 hours, equilibrium concentration was obtained by removing 1mL of the supernatant from each

cosolvent, put in a vial containing 5 mL of cocktail (Scinti-Verse II scintillation solution) and

analyzed using a Beckman LS 100-C liquid scintillation counter (LSC). The analyzing time was

5 minutes. Back ground radioactivity from a blank of methanol + calcium chloride solution was

subtracted from each LSC counts of the sample. Equations 3-1 to 3-6 and 3-9 were used to

calculate properties of DDT (cosolvency power, percent of a chemical recovered from the Teflon

lined centrifuge tubes, sorption coefficient in water, and HSA).









Sorption Isotherms on Soils

Before sorption isotherm experiments were done, an experimental design was carried out

to make sure that a maximum equilibrium concentration (Ce) was maintained at all f values and

in all soils for a given chemical.

Estimation of equilibrium concentrations

All sorption isotherms from soils were designed such that equilibrium concentrations (Ce)

at each f and in each soil were in the linear range of isotherms. This was achieved by using the

Solvophobic model to calculate the solubility of each chemical at f values from 0 to 0.7. The

model was also used to estimate sorption coefficients at each f based on literature Koc values.

Using the linear isotherm model, the chemical's Koc and f values the following equations

were derived:

Se = KM Ce 3-12

Se = V/m (Co-Ce) 3-13

Parameters in Eqs. 3-12 and 3-13 have been defined earlier. Combining Eqs. 3-12 and 3-

13 yield an equation that can be used to vary the soil: solution ration at all f' values to maintain

the required Ce range.

Ce = C/((m/V*KM )+ 1) 3-14

In order to maintain the same Ce range Eq.3-14 was used. This was achieved by adjusting

Co, m, and KM depending on f of methanol at which the isotherm was measured. A summary of

the various parameters used during isotherm determination is given in Table 3 -3.

Sorption of anthracene on soils

Equilibrium sorption isotherms were measured from various mixtures of methanol and

water using four soils (Krome, Perrine and Chekika, and Lauderhill). Isotherms were determined

in the range of methanol (f = 0.5 to 0.7) when there was no sorption on TLCT. The soil solution









ratios of 1:2, 1:1.2.5, and 1:1 were used for methanol fractions of 0.5, 0.6 and 0.7, respectively,

for carbonatic soils. Initial concentrations of 12C-Anthracene were 0.1, 0.2, 0.4 ([tg/mL) for f =

0.5, 0.6 and 0.7. The soil solution ratio at f = 0.5, 0.6 and 0.7 were 1:1, 1:40, and 1:17,

respectively for Lauderhill. The soil solution ratios at f = 0.5, 0.6 and 0.7 were 1:67, 1:25, and

1:13, respectively, for Monteocha. All isotherms were run in triplicates for each initial

concentration and at a given f. The solutions were spiked with 14C-Anthracene to give (10,000

cpm/mL).

Following a 24 h shaking and equilibration period, the solution phase was separated from

the solid phase by centrifugation at 9000 rpm for 25 minutes and ImL of the supernatant was put

in a 5 mL of cocktail in plastic vials. Liquid scintillation counting (LSC) was used to analyze

14C-Anthracene in solution. The counting time was 5 minutes. Background radioactivity from a

blank of methanol + calcium chloride solution was subtracted from counts of the sample. The

decrease in sorbate solution concentration was assumed to be due to sorption by the soil.

Additional sorption experiments by Krome soil were carried out at f = 0.1, 0.2, and 0.3

with soil solution ratios of 0.01, 0.02, and 0.1, respectively. The total volume of solution was 10

mL.

All isotherms were done in triplicates. The additional data were collected to test the

linearity of the Solvophobic model by directly determining anthracene adsorbed on the soils. The

initial 12C-Anthracene concentration was 0.1 to 0.2 (atg/mL), and 14C-Anthracene was 40, 000

cpm/mL. Due to potential sorption on TLCT, the batch slurry method was modified. The amount

of 14C-Anthracene adsorbed on the soil was directly determined by combusting an oven dry sub-

sample of the soil at the end of the equilibration period after centrifuging the samples at 9000

rpm for 25 minutes and determining Ce in the supernatant solution by LSC. The soil sample was









combusted in a Harvey Ox 500 Biological oxidizer, trapping the evolved CO2 in a scintillation

solution and quantifying 14CO2 by liquid scintillation as described earlier. The adsorbed

concentration (Se) was calculated using Eq.3-13 and was plotted against the solution

concentration (Ce). The slope of the line is equal to the sorption coefficient (KM) based on Eq. 3-

12. Equations 3-1, 3-9, and 3-10 were used to calculate properties of Anthracene (cosolvency

power, 0), sorption coefficient in water (Kw), and HSA. The values ofKw were normalized

with soil organic carbon content to calculate Koc for each soil.

Sorption of DDT on soils

Methanol fractions (f) of 0.5, 0.55, and 0.6 were used for all soils. Initial concentrations of

12C-DDT were 0.02 to 0.04 ([tg/mL) for all methanol fractions used. The soil solution ratios at f

= 0.5, 0.55 and 0.6 were 1:3, 1:2 and 1:1 respectively for Krome, Chekika and Perrine. The soil

solution ratios at f =0.5, 0.55 and 0.6 were 1:50, 1:29 and 1:20, respectively for Monteocha soil.

The soil solution ratios at f = 0.5, 0.55 and 0.6 were 1:100, 1:67 and 1:50, respectively for

Lauderhill soil. The total volume of solution was 10 mL, and the samples were spiked with 14C-

DDT to give 40, 000 cpm/mL.

Following a 24hr shaking and equilibration period, the solution phase was separated from

the solid phase by centrifugation at 9000 rpm for 25 minutes and ImL of the supernatant was put

in a 10mL of cocktail in plastic vials. Liquid scintillation counting (LSC) was used to analyze the

solution. The analyzing time was 5 minutes. The decrease in sorbate solution concentration was

assumed to be due to sorption by the soil.

The adsorbed concentration (Se) was calculated using Eq. 3-13 and was plotted against

the solution concentration (Ce). The slope of the line is equal to the sorption coefficient (KM)

based on Eq.2-12. Equations 3-1, 3-9, and 3-10 were used to calculate properties of DDT









(cosolvency power (c5), sorption coefficient in water (Kw), and HSA). The values of Kw were

normalized with soil organic carbon content to calculate Koc for each soil.

Sorption of dieldrin on soils

Equilibrium sorption isotherms were measured from various mixtures of methanol and

water. Methanol fractions of 0.4, 0.45, 0.5 and 0.6 were used. Soil solution ratios of 1:2.5, 1:2,

1:1.3, and 1:1 for f = 0.4, 0.45, 0.5 and 0.6, respectively, were used for Perrine, Krome and

Chekika soils. Methanol fractions of 0.4, 0.5 and 0.6 were used for Lauderhill and Monteocha

soils at solution ratios of 1:17, 1:6, and 1:3. The three initial concentrations of dieldrin were

between 4 to 8 pg/mL. The total volume of solution in TLCT was 10 mL. At each f and initial

concentration, triplicate soil samples were used.

Following a 24h shaking and equilibration period, the solution phase was separated from

the solid phase by centrifugation at 9000 rpm for 25 minutes. The supernatant was added to

HPLC vials and diluted by methanol to reach (fc = 0.7) when there was no sorption on HPLC

vials. The solution was analyzed by HPLC with UV detection. Conditions of the HPLC system

were; wavelength of220nm, sensitivity of 0.04Aufs, flow rate of 1.5mL/min; mobile phase of

80%methanol and 20%water, and C-18 column. All the standards and the samples were added to

HPLC vials in methanol to make up 1 mL of at least 70% methanol. Samples were injected thrice

in the HPLC system. The run time was 8 minutes and retention time was 6 minutes.

Concentrations that were below detection limit after dilution of samples in HPLC vials were

spiked with a known concentration of dieldrin in pure methanol.

The adsorbed concentration (Se) was calculated using Eq.3-13 and was plotted against the

solution concentration (Ce). The slope of the line is equal to the sorption coefficient (KM) based

on Eq.12. Equations 3-1, 3-9, and 3-10 were used to calculate properties of Dieldrin (cosolvency









power (c5), sorption coefficient in water (Kw), and HSA). The values ofKw were normalized

with soil organic carbon content to calculate Koc for each soil.









Table 3-1: Characteristics of the soils used


Soil series name
Chekika

Krome

Perrine, marl

Lauderhill
Monteocha


Location
Miami Dade County,
Florida
Miami Dade County,
Florida
Miami Dade County,
Florida
Miami Dade County
Alachua County, Florida


Classification
Loamy-skeletal, carbonatic, hyperthermic
Lithic Udorthents.
Loamy-skeletal, carb onatic,hyperthermic
Lithic Udorthents
Coarse-silty,carbonatic,hyperthermic Typic
Fluvaquents
Euic hyperthermic Lithic Haplosaprists
Sandy, siliceous hyperthermic Ultic Alaquods
Monteocha


Some properties of the solvents (at 250C) used
Boiling Surface
Point Viscosity Tension Density
(C) (cP) (dyne/cm) (g/mL3)


Rohrschneider
Polarity index


Water 100 0.89 73 1.0 9.0 1.84 80.0
Methanol 65 0.54 22 0.77 6.6 1.66 32.7
Source: Snyder et al. (1978)




Table 3-3. Summary of initial and equilibrium concentrations used for sorption isotherms
ft range for Co Ce range
Chemical Type isotherm (ug/mL) (ug/mL) Sorbent(s)


P-endosulfan
Dieldrin
Dieldrin
Dieldrin
Anthracene
Anthracene
DDT
DDT


dC
12C
12C
12C
; and14C
Sand14C
; and14C
Sand14C


0.1-1
0.25 0.4
0.1 -0.6
0.3-0.6
0.01 -0.6
0.5 -0.7
0.05 0.5
0.5 -0.6


11
2.5- 5
2-3
4-8
0.1
0.1
0.01 0.02
0.02 0.04


5-9
1-2.5
1 -2.5
1.3 -2.6
0.05 -0.09
0.01-0.06
0.009 0.02
0.009 0.02


HPLCV + TLCT
HPLCV
TLCT
Soils
TLCT
Soils
TLCT
Soils


Table 3-2.
Solvent


Dipole
Moment
(D)


Dielectric
constant



























Figure 3-1. Sorption of a chemical up to HPLC analysis


Figure 3-2. Sorption of a chemical up to LSC analysis
























Figure 3-3. Calculation of the area of HPLC vials covered by solution


1


Area: 4.76CM2

Volume = 1mL
Radius = 0.5cm

Height = 1.25cm
















F




|
P
5


I
W




g
1 i




wTn


~--- ~~ouoL


~ Iwub


~ ~wuL


~ O~bn~b


~ P~nnb

~ BooeL


5mL = 2.26CM

I m = M


Figure 3-4. Calculation of the area of Teflon Lined Centrifuge Tubes covered by solution









CHAPTER 4
RESULTS AND DISCUSSION

In this study, initially, sorption of P-endosulfan, dieldrin, anthracene, and DDT, on

container walls (Teflon lined centrifuge tubes and HPLC vials) in methanol-water systems with

methanol ranging from (f = 0.01 to 1) were determined. Then the range of fraction of methanol

(f) where there was no sorption on container walls was identified. Above that range of methanol

f, sorption coefficients (KM) of anthracene, DDT, and dieldrin, were determined in five soils

(Perrine, Krome, Chekika, Lauderhill and Monteocha). The aqueous (f = 0) sorption coefficient

(Kw) of each chemical was calculated using the Solvophobic model. The Kw values were

normalized with soil organic carbon content to obtain Koc values for each chemical in all soils.

The parameters that were used to calculate HSA, Koc, and KM of each chemical are listed in

Table 4-1.

Sorption on Container Walls

Sorption of 12C-P-endosulfan on Teflon Lined Centrifuge Tubes (TLCT) and HPLC Vials
(HPLCV).

Data in Figs. 4-1 and 4-2 show that P-Endosulfan adsorbed on the container walls (TLCT

and HPLCV) up to 0.5 f with little sorption at f = 0.7. Data in Figs. 4-1 and 4-2 also reveal that

the Solvophobic model describe the data reasonably well. The percent recovery in water (f = 0)

was calculated as 30%. The sorption coefficient of P-endosulfan in an aqueous system (Kw) from

Figure 4-1 was 0.60 ug/cm2. Although sorption on container walls is not needed, sorption on

container walls was used to calculate HSA for p-endosulfan of 176 A2 using Eq. 3-9 and

parameters listed in Table 4-1. No data are available in the literature for p-endosulfan HSA or

TSA. Nkedi-Kizza et al., (1985) pointed out that the value of the slope of the line in Fig. 4-1

depends on the properties of methanol, water, and P-endosulfan, and therefore the HSA

calculated should not be affected by the nature of the sorbent. However, the magnitude of Kw









calculated depends on the properties of the sorbing materials, in this case TLCT and HPLC vials.

In many studies of organic chemicals, TLCT and HPLCV are assumed not to adsorb chemicals

such as P-endosulfan. The data presented show that the concentration of P-endosulfan if

measured in aqueous system with HPLC-UV would be reduced by 70%.

Sorption of 12C-Dieldrin on Container Walls

Sorption on HPLC vials (HPLCV) and Teflon lined centrifuge tubes (TLCT)

The dependence of KM on f for dieldrin sorption by two container walls (TLTC and

HPLCV) is shown in Fig. 4-3. As predicted by the Solvophobic theory (Eq. 3-1) a log-linear

relationship describes the data over the range of 0.1 f > 0.5. The slopes of the lines in Fig. 4-3

are essentially the same, indicating that the value of ac (Table 4-1) is independent of the sorbent

as predicted by Eq. 3-1. Similar trend in data was reported for anthracene sorption on 4 soils in

methanol-water systems (Nkedi-Kizza, et al., 1985).

The calculated aqueous sorption coefficient values ( Kw) for Dieldrin were 0.57 and 3.24

[tg/ cm2 on TLCT and HPLV container walls, respectively. Data in Figs. 4-4 and 4-5 further

emphasize that HPLCV sorb more dieldrin than TLCT. The percent recovery in aqueous systems

was estimated as 6 and 32% for HPLCV and TLCT, respectively. Another observation is that

dieldrin is not adsorbed on HPLCV at fC > 0.70 compared to TLCT in which there is no sorption

of dieldrin at f> 0.45. The implications are that sorption experiments of dieldrin should be

determined in methanol at f> 0.45 to eliminate sorption on TLCT. However, for the analysis of

dieldrin with HPLC-UV, the analyte in HPLC glass vials should be in methanol at f > 0.70. The

data in Figs. 4-4 and 4-5 describe the percent recovery well as predicted by the theory (Eq. 3 -6).

In Fig. 4-6, the plot of the relative sorption coefficient [In (KM/Kw)] VS. f is shown for

Dieldrin sorption on HPLCV and TLCT container walls. The sorption data from TLCT and

HPLC vials are described by one line as expected from Eq. 3-1. The cd value calculated from the









slope of the line in Fig. 4-6 (using a' = 0.83) was 10.69 which was close to ac value of 10.67 and

10.75 for HPLCV and TLCT, respectively. The c values were used to calculate HSA of dieldrin

using Eq. 3-9 and appropriate values of (Ay', k, and T) listed in Table 4-1. The HSA for dieldrin

was 221 A2 (Table 4-2).

Sorption of 14C-Anthracene on Teflon Lined Centrifuge Tubes (TLCT)

The dependence of KM on f for anthracene sorption by container walls of TLCT is shown

in Fig. 4-7. As predicted by the Solvophobic theory (Eq. 3-1) a log-linear relationship describes

the data over the range of 0.1 < fc < f' 0.25. The line was extended to f = 0 to estimate Kw. The

calculated aqueous sorption coefficient ( Kw) value for anthracene on TLCT container walls was

0.54 agg/ cm2. The percent recovery (in aqueous systems) for sorption of anthracene on TLCT

container walls was estimated to be 52% (Fig. 4-8). Anthracene is not adsorbed on TLCT at f >

0.45. This implies that sorption experiments on anthracene should be determined in methanol-

water mixtures at fe > 0.45 to eliminate sorption on TLCT.

The o value calculated from the slope of the line in Fig. 4-6 (using ac = 0.83) was 9.83.

The o values were used to calculate HSA of anthracene using Eq. 3-9 and appropriate values of

(Ay', k, and T) listed in Table 4-1. The HSA for anthracene was 203 A2 very close to the

literature value of 202 A2 (Nkedi-Kizza et al., 1985). Since anthracene has no functional groups,

its TSA is equal to HSA. This gives credibility to the use of the Solvophobic model in this study.

Sorption of 14C-DDT on Teflon Lined Centrifuge Tubes (TLCT)

The dependence of KM on f for DDT sorption by container walls of TLCT is shown in

Fig. 4-9. As predicted by the Solvophobic theory (Eq. 3-1) a log-linear relationship describes the

data over the range of 0.05 < f < 0.30. The line was extended to f = 0 to estimate Kw. The

calculated aqueous sorption coefficient (Kw) value for DDT on TLCT container walls was 0.67

tg/ cm2. The percent recovery (in aqueous systems) for sorption of DDT on TLCT container









walls was estimated to be 29% (Fig. 4-10). DDT is not adsorbed on TLCT at f > 0.45. This

implies that sorption experiments on DDT can be determined in methanol-water mixtures at f >

0.45 to eliminate sorption on TLCT.

The c value calculated from the slope of the line in Fig. 4-6 (using a' = 0.83) was 12.94.

The o values were used to calculate HSA of DDT using Eq. 3 -9 and appropriate values of (Ay,

k, and T) listed in Table 4-1. The HSA for DDT was 322 A2 No data in the literature are

available for comparison.

Conclusions

Sorption of four strongly hydrophobic chemicals on container walls of Teflon lined

centrifuge tubes and HPLC vials has been demonstrated. Using dieldrin sorption data on HPLC

vials and Teflon lined centrifuge tubes; HPLC vials sorb more dieldrin than Teflon lined

centrifuge tubes in aqueous systems. This was confirmed by low recovery of P-endosulfan that

was sorbed on both TLCT and HPLCV. In aqueous systems, the sorption on TLCT container

walls was predicted to be in the order DDT > Dieldrin > Anthracene (Table 4-2). For all three

SHOCs there was negligible sorption on TLCT at f > 0.45. However, it is clear that glass HPLC

vials sorb these chemicals at f1 < 0.7.

To eliminate sorption on Teflon lined centrifuge tubes and to determine soil sorption

coefficients of dieldrin, DDT, and anthracene in these tubes, experiments should be conducted in

methanol-water mixtures at f > 0.45. If HPLC-UV is the method of detection of SHOCs in

solution, the analyte should be prepared in methanol or other miscible solvents at fc > 0.7.

Literature data that support findings in this study have reported that 40-80% of the poly

chlorinated biphenyls (PCBs) in a sample may be adsorbed on to the poly tetrafluoroethylene

(PTFE) surface (Baltussen et al., 1999, Lung et al., 2000).









It was interesting to find that the hydrocarbonaceous surface areas of p-endosulfan,

dieldrin, DDT, and anthracene could be calculated from sorption data on container walls. The

HSA values are summarized in Table 4-2. It appears that the Solvophobic model was appropriate

for this study.

Sorption Isotherm Experiments

Sorption isotherm experiments for sorption of chemicals by soils were carried out to

determine sorption coefficients in mixed solvents (KM) and there after extrapolate to aqueous

systems using the Solvophobic model to obtain sorption coefficients (Kw). Then soil sorption

ceoefficient values (Koc) were calculated by dividing Kw with organic carbon fractions (OC) of

soils. Sorption data on soils were also used to calculate hydrocarbonaceous surface areas (HSA)

of the chemicals.

Sorption of Dieldrin on Soils

The exponential decrease in sorption coefficients (KM) of dieldrin in mixed solvents with

increasing methanol fractions (f) is shown in Fig. 4-11, for 5 soils. The slopes of these lines are

essentially the same because the cosolvency power (c) is independent of the sorbents (soils)

used. Plots of relative sorption coefficients (KM/Kw) for all soils were therefore described as a

single line (Fig. 4-12) from which effective HSA was calculated. The soil sorption coefficients

in aqueous systems (Kw) were calculated from the intercepts of the plots (Fig. 4-11). Similar

trend in data were reported for sorption of diuron and atrazine in soils (Nkedi-Kizza et al., 1985).

The (dc) values from sorption of dieldrin by Chekika, Krome, Perrine, Lauderhill, and

Monteocha, were used to calculate HSA values. The HSA values were very close to the effective

HSA calculated from all soils of 222 A2. The data are summarized in Table 4-3. The HSA values

are also close to those determined for dieldrin sorption on container walls (Table 4-2).









From literature, sorption is directly proportional to organic carbon content of the soil. The

trend of sorption coefficients in aqueous systems (Kw) as shown in Table 4-3 is proved to be true

for all soils. When sorption coefficients in aqueous systems (Kw) were normalized with organic

carbon content of the soils to obtain soil Koc values, all soils except Krome gave values close to

each other (Figure 4-13). However, dieldrin sorption coefficient value in Krome is within a

factor of two (Karickhoff, 1981). The low organic carbon content (Karickhoff, 1984) of Krome

can explain the deviation of dieldrin Koc value from other soils. Data in Fig.4-14 show an

average Koc of 4803 for all soils. The Koc values obtained in this study are much less than what

is reported in the literature (Table 2-2) which implies that sorption on container walls is a factor

for the variation of Koc values of strongly hydrophobic organic chemicals.

Sorption of Anthracene on Soils

Sorption of anthracene on soils was done to show the validity of Solvophobic model.

Anthracene served as an ideal sorbate for evaluating the Solvophobic theory because its sorption

is characterized by solvophobic interactions since the hydrocarbonaceous surface area, HSA, is

equal to total surface area, TSA. The exponential decrease in sorption coefficients (KM) in mixed

solvents with increasing methanol fractions (f) is shown in Fig. 4-15 for Krome soil. The KM

data in Fig. 4-15 were obtained at 0.45 < f < 0.8 where there is negligible sorption of anthracene

on TLCT container walls. These data were used in the model. The KM values for anthracene

sorption at f = 0.1, 0.2 and 0.3 were directly measured by combustingl4C-Anthracene to

determine the amount adsorbed on the soil. The KM values at f = 0.1, 0.2, and 0.3 are also

described by the theory (Eq. 3-1). This emphasizes that KM data collected at f >> 0 can be used

to estimate Kw at f = 0. However, if sorption on container walls is ignored, the KM values

measured at f = 0.1, 0.2, and 0.3 will give a very high Kw (1012 mL/g)) resulting in anthracene

Koc of 101, 200. This Koc value is about 5 times larger than the Koc of 18752 that was obtained









for anthracene sorption by Krome that when there was no sorption on container walls on

container walls (Table 4-4).

The dependence of KM values on ft for Anthracene sorption by four soils from methanol-

water mixtures at which there no sorption on TLCT walls is shown in Fig. 4-16. As predicted by

the Solvophobic theory (Eq. 3-1), a log-linear relationship describes the data for all soils. The

slopes of the lines are essentially the same because the cosolvency power (c) is independent of

the sorbents (soils). Plots of relative sorption coefficients (KM/Kw) for all soils were therefore

described as a single line (Figure 4-17) from which effective HSA was estimated as 203 A2. The

HSA values from sorption of anthracene on Krome, Chekika, Perrine, Monteocha, and

Lauderhill (Table 4-4) were very close to the value of 202 A2 that is reported in the literature

(Yalkowsky et al., 1979). The HSA values are also close to the values obtained for the sorption

of Anthracene on TLCT container walls (Table 4-2).

As was observed for dieldrin sorption in soils, sorption is proportional to organic carbon

content of the soil. The trend of sorption coefficients in aqueous systems (Kw) can be seen

(Table 4-4). Since soil organic carbon increases in the order Lauderhill> Perrine> Chekika >

Krome, the KM values also increase in the same order. When Sorption coefficients in aqueous

systems (Kw) were normalized with organic carbon content of the soils to obtain Koc values, the

values did not give constant figures across all the soils. Although most of the values are with in

the acceptable factor of two, some go beyond that factor. The low organic carbon content

(Karickhoff, 1984) of the carbonatic soil Krome might have caused the difference in Koc values

as was also observed for dieldrin sorption in Krome. As was observed for dieldrin sorption,

Perrine soil has the lowest Koc value for Anthracene. The average anthracene Koc value for all









the soils of 8886 was obtained from the slope of the plot of sorption coefficients in aqueous

systems (Kw) against the organic carbon content as shown in Figure 4-19.

Sorption of DDT on Soils

The exponential decrease in sorption coefficients (KM) in mixed solvents with increasing

methanol fractions (f) is shown in Fig. 4-20 for Krome soil. The KM data in Fig. 4-19 were

obtained at 0.50 < f < 0.7 when there is negligible sorption of DDT on TLCT container walls.

These data were used in the model. The KM values for DDT sorption at f = 0.3, and 0.4 were

directly measured by combusting14C-DDT to determine the amount adsorbed on the soil. The KM

values at f = 0.3 and 0.4 are also described by the theory (Eq. 3-1). This implies that KM data

collected at fc >> 0 can be used to estimate Kw at f = 0. A similar trend in data was observed for

anthracene sorption in Krome soils.

The exponential decrease in sorption coefficients (KM) in mixed solvents with increasing

methanol fractions (f) is shown in Figures 4-21 with slopes of the lines essentially the same.

This further demonstrates that cosolvency power (dc) is independent of soils.

Plots of relative sorption coefficients (KM/Kw) for all soils were therefore described as a

single line (Figure 4-22). The value of ao from Fig. 4-22 was used to calculate the HSA of DDT

which was 322 A2. The HSA values from sorption of DDT by Chekika, Krome, Perrine,

Lauderhill, and Monteocha soils were 323, 326, 319, 319, 324, and 319A2, respectively, as

shown in Table 4-5. Note that a similar HSA value of 322 A2 was obtained from DDT sorption

on TLCT container walls.

From literature data, sorption is proportional to organic carbon content of the soil (Table 4-

1). The trend of sorption coefficients in aqueous systems (Kw) as shown in Table 4-2 is generally

proved to be true for all soils. When Sorption coefficients in aqueous systems (Kw) were

normalized with organic carbon content of the soils to obtain Koc values, the data were within a









factor of two for three soils (Krome, Monteocha, and Lauderhill). The two other carbonatic soils

had Koc values lower than a factor of three. Such low Koc values for Perrine and Chekika have

been reported for diuron and atrazine (Nkedi-Kizza et al., 2006). The average Koc from all soils

was calculated to be 195,665. The Koc values obtained from this study for DDT are much lower

than those reported in the literature (Table 2-1). The Koc values from this study varied within a

factor of 4 compared to a factor of 13 reported in the literature (Table 2-1). This implies that

sorption on container walls might be a serious cause of variability in literature Koc values for

DDT.

Conclusions

DDT sorbed most on the soils followed by Anthracene and the least sorption was observed

for dieldrin, which is a reflection of aqueous solubility of these chemicals. The three chemicals

have very low aqueous solubility which makes it difficult to measure sorption in water. All three

chemicals would strongly sorb on Teflon lined centrifuge tubes and HPLC vials in aqueous

systems. Consistent sorption data in soils for SHOCs can be obtained while measuring sorption

in mixed solvents that will eliminate sorption on container walls and vessels.









Table 4-1. Parameters used to calculate chemical properties (HSA, Koc, and KM)
Parameter/Soil Value Source
Ayc (erg/A2) 1.99*10-1 Nkedi-Kizza et al. (1985)
k (ergs/K) 1.38*10-16
T 298 (K) Room temperature
ac 0.83 Karickhoff, (1981)
Chekika-OC (g/g) 0.02 This study
Krome-OC (g/g) 0.01 This study
Perrine-OC (g/g) 0.03 This study
Monteocha-OC (g/g) 0.07 This study
Lauderhill-OC (g/g) 0.31 This study
TLCT-surface area for 10 mL (A, cm2) 38.53 This study
HPLCV-surface area for 1 mL (A, cm2) 4.76 This study


Table 4-2 Sorption ofDDT, p-endosulfan, Anthracene and Dieldrin on containers.
Chemical K" % Recovery 100 % HAS
(Sorbent) (pg/cm2) at f = 0 recovery f ac (A2)
Endosulfan(HPLCV+TLCT) 0.60 30 70 8.65 176
Dieldrin(HPLCV) 3.24 6 70 10.67 221
Dieldrin(TLCT) 0.57 32 45 10.75 221
Dieldrin (TLCT and HPLCV) NA NA NA 10.69 221
DDT(TLCT) 0.67 29 45 15.59 322
Anthracene (TLCT) 0.24 52 45 9.81 203
NA = Not applicable









Table 4-3. Sorption coefficients (Kw and Koc), cosolvency powers (ac) and hydrocarbonaceous
surface area (HSA) for Dieldrin
Parameter Perrine Chekika Krome Monteocha Lauderhill All soils
Kw (L/kg) 119 99 86 314 1495
Ca 10.72 10.71 10.67 10.98 10.51 10.72
HSA (2) 222 221 221 227 217 222
Koc (L/kg) 3961 4,945 8,566 4,478 4,823 4,803


Table 4-4. Sorption coefficients (Kw and Koc), cosolvency powers (dc) and hydrocarbonaceous
surface areas (HSA) for Anthracene
Parameter Perrine Chekika Krome Lauderhill All soils
KW(L/kg) for f= 0.5, 0.6, 0.7 110 128 188 2770
Koc (L/kg) for f =0.5, 0.6, 0.7 3,669 6,418 18,752 8,935
K (L/kg) for f =0.1,0.2, 0.3 NA NA 1012 NA
Koc (L/kg) for = 0.1, 0.2, 0.3 NA NA 101200 NA
ac 9.83 9.78 9.86 9.78 9.81
HSA(A2) 203 202 203 202 203
Koc (L/kg) for f = 0.5, 0.6, 0.7 8,886
NA = Not applicable





Table 4-5. Sorption coefficients (Koc), cosolvency powers (c) and hydrocarbonaceous surface
areas (HSA) for DDT
Parameter Perrine Chekika Krome Monteocha Lauderhill All soils
KW(L/kg) 1,703 1,236 2,101 11,614 61,698 NA
Koc (L/kg) 56,758 61,823 210,065 165,920 196,489 195,665
(oc) 15.43 15.58 15.76 15.43 15.67 15.59
HAS (A2) 319 323 326 319 324 322
NA = Not applicable











P-Endosulfan Sorption on Teflon Limned Centrifuge Tubes and HPLCV
Model [Y= -7.18X-0.52; R2 =0.9990];Kw = 0.60 pg/cm2; HSA = 176A2
0

-1

-2

-3
Data
-4 Model

-5

-6 11
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

VOLUME FRACTION METHANOL (f)

Figure 4-1. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of P-Endosulfan by Teflon Lined Centrifuge Tubes and HPLC Vials


P-Endosulfan Recovery from Sorption on Teflon Lined Centrifuge
Tubes and HPLC Vials. In Water %R = 30. No Sorption at fc > 0.70


120

100 --

Sso -
W Data
0 60 -[je
0 -- Model
S40

20 -
20

0I I I I I
0 0.2 0.4 0.6 0.8 1 1.2

VOLUME FRACTION METHANOL (fc)


Figure 4-2 Percent recovery of P-Endosulfan sorption on Teflon Lined Centrifuge Tubes and
HPLC Vials










Dieldrin Sorption on TLCT and HPLCV
KW: TLCL = 0.57 pg/cm2; HPLCV = 3.24 pg/cm2


2
1 TLCT-Data
Y= -8.86X + 1.18 TLCT-Data
0 HPLCV-Data
S-1 Model-TLCT
S-2 Modle-HPLCV
-3 Linear (Model-TLCT)
-4 Y =-8.92X 0.57 Linear (Modle-HPLCV)
-5 I I I
0 0.2 0.4 0.6 0.8

VOLUME FRACTION METHANOL (f)

Figure 4-3. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of Dieldrin by Teflon Lined Centrifuge Tubes and HPLC Vials


Dieldrin Recovery from Sorption on HPLCV
In water % R = 6. No sorption at f > 0.70

120

100 -

S80-

60 -
60 Data-HPLCV
S40 -Model

20

0I I I I
0 0.2 0.4 0.6 0.8 1

VOLUME FRACTION METHANOL (f)

Figure 4-4. Percent recovery of Dieldrin sorption on HPLC Vials










Dieldrin Recovery from Sorption on TLCT
In Water % R = 32. Little Sorption at fC > 0.45

100


S80 -

60
C* Data-TLCT
S40 Modle

420
20

0I I I I
0 0.2 0.4 0.6 0.8 1

VOLUME FRACTION METHANOL (f)

Figure 4-5. Percent recovery of Dieldrin sorption on Teflon Lined centrifuge Tubes (TLCT)


Dieldrin Sorption on TLCT and HPLCV
KW: TLCT = 0.57 pg/cm2; HPLCV= 3.24 pg/cm2

2


^* TLC T-Data
S-2 HPLCV-Data
.2 -- Model-TLC T
M -. --- Modle-HPLCV
-4 "

-6 I I I
0 0.2 0.4 0.6 0.8

VOLUME FRACTION METHANOL (f)



Figure 4-6. Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (fe) for
Dieldrin sorption by Teflon Lined Centrifuge Tubes and HPLC Vials.














Anthracene Sorption on Teflon Lined Centrifuge Tubes
[Model Y = -8.16X-1.43; R2 = 0.9552]; Kw= 0.24 ug/cm2; HSA = 203A2

0

-1

-2
-2 -I + D a ta
-3 ~ Model
c -3

-4

-5 I I I I I I
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

VOLUME FRACTION METHANOL (f)

Figure 4-7. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of Anthracene by Teflon Lined Centrifuge Tubes.




Anthracene Sorption on Teflon Lined Centrifuge Tubes

In Water %R = 52. Negligible Sorption at f > 0.45


Figure 4-8. Percent recovery of Anthracene sorption on Teflon Lined centrifuge Tubes


'K


120


100


80


60


40


20


0
-


I I I I 1
0.2 0.3 0.4 0.5 0.6

VOLUME FRACTION METHANOL (f)


0 0.1


* Data
-- Model











Sorption of DDT on Teflon Lined Centrifuge Tubes
[Model Y = -12.94X 0.40; R2= 0.9927]
Kw = 0.67t1g/cm2; HSA = 322A2

0

-1

-2

-3 Data
Model
-4

-5

-6 i i i i i i i i
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45
VOLUME FRACTION METHANOL (fC)

Figure 4-9. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption ofDDT by Teflon Lined Centrifuge Tubes



DDT Recovery from Sorption on TLCT

In Water % R = 29. Little sorption at fe > 0.45



120

100 -

P4 80 -
+* Data
0 60 Model

W 40

20 -
20

0 II IiI

0 0.1 0.2 0.3 0.4 0.5 0.6

VOLUME FRACTION METHANOL (f)


Figure 4-10. Percent Recoveries of Dieldrin sorption on Teflon Lined Centrifuge Tubes





































Figure 4-11. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption ofDieldrin by soils


Dieldrin Sorption on Soils
[Model Y = -8.90X, R2 = 0.9968]; HSA = 222 A2

0

-1
Chekika
-2
2 Krome
-3 Perrine
-4 Lauderhill
-5 x Monteocha
Model
-6

-7 I I I I I
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

VOLUME FRACTION METHANOL (f)


Figure 4-12. Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (f) for
Dieldrin sorption by soils.


Dieldrin Sorption on Soils


8
8 |------------------.






4-


2





-2 I I
0 0.2 0.4 0.6

VOLUME FRACTION METHANOL (fc)


Lauderhill
Monteocha
Perrine
Chekika
Krome
- Linear (Lauderhill)
Linear (Monteocha)
Linear (Perrine)
- Linear (Chekika)
-- Linear (Krome)











Dieldrin Sorption Coefficient (Kw) Normalized with OC: [Koc = KM/OC]

10000
8566

8000

6000 /
6000 4945 4823
O6 4479
3961
4000

2000



Perrine Chekika Krome Monteocha Lauderhill

SOIL SERIES

Figure 4-13. Dieldrin KOC from different soils


Dieldrin Sorption Coefficient in Soils [Koc = 4803 184 ]


1600
Y=4803X
R2 = 0.9984
1200


U >- 800

S* Data
400 Linear (Data)


0 T

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

SOIL ORGANIC CARBON CONTENT (OC, g/g)

Figure 4-14. Relationship between the sorption coefficient (Kw) and soil organic carbon content
(OC) for sorption of Dieldrin by soils











Anthracene-Krome Sorption

[Model Y = -8.18X + 5.24; R = 0.9997]
Kw = 187.52 L/kg ; Kw = 1012 L/kg including sorption on TLCT


6


5


4

Data
Sfc-0.1
fe=0.2
fc-0.3
_- Model
1


0


-1


-2 I I
0 0.2 0.4 0.6 0.8

VOLUME FRACTION METHANOL (fC)


Figure 4-15. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f') for sorption of Anthracene by Krome soil.












Anthracene Sorption on Soils


10



8 -
Chekika
Perrine
6 Krome
x Monteocha
Laudehill
4 ....------- Modle-Perrine
Model-Krome
2' Model-Chekika
--- Modle-Lauderhill
S-- Model-Monteocha
0



-2 I I
0 0.2 0.4 0.6 0.8

VOLUME FRACTION METHANOL (f)


Figure 4-16. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of Anthracene by soils











Anthracene Sorption on Soils
[Model Y= -8.12X; R2 = 0.9995]; HSA = 202.10 A2

0


-1


-2


S-3 Data-Chekika
U Data-Perrine
S-4 Data-Krome
Data-Monteocha
-5 x Laudehill
-- Model

-6


-7 I I I I
0 0.2 0.4 0.6 0.8 1

VOLUME FRACTION METHANOL (f)


Figure 4-17. Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (f') for
Anthracene sorption by soils.











Athracene Soil Koc


24000

20000 18752

16000

O 12000
8935
8000 6418
3669
4000

0
Perrine Chekika Krome Lauderhill

SOIL SERIES

Figure 4-18. Anthracene Koc values from different soils


Figure 4-19. Relationship between the sorption coefficient (Kw) and soil organic carbon content
(OC) for sorption of Anthracene by soils


Sorption Coefficient (KM) Normalized to OC
Koc = 8886 854


3000
M Y=8886 X
2500- R2= 0.9935

S 2000 -
C E

S 1500 -

1000

0 500

0
0 0.05 0.1 0.15 0.2 0.25 0.3

ORGANIC CARBON CONTENT (OC, g/g)


0.35











DDT Sorption On Krome
[Model Y = 13.08 X + 7.12; R2 = 1]


8

6

4 Data

2
Sfc = 0.4
0 -Model

-2

-4 I I
0 0.2 0.4 0.6 0.8

VOLUME FRACTION METHANOL (fC)


Figure 4-20. Log-linear relationship between sorption coefficient (KM) and fraction of methanol
(f) for sorption of DDT by Krome soil.


Figure 4-21. Log-linear relationship between sorption coefficient
(f) for sorption of DDT by soils.


(KM) and fraction of methanol


Sorption of DDT on Soils


12

10


6

4

2

0

-2

-4I I
0 0.2 0.4 0.6

VOLUME FRACTION METHANOL (f)


Lauderhill
- Lauderhill-Model
Monteocha
- Monteocha-Model
x Krome
Krome-Model
+ Perrine
-- Perrine-Model
o Chekika












Sorption of DDT on Soils

[Model Y= 12.94X; R2 = 0.9975]; HSA = 322A2




0

-2 Model
Chekika
S-4 Perrine

-6 -1 Krome
64 x Monteocha
-8 Lauderhill

-10 I I
0 0.2 0.4 0.6 0.8

VOLUME FRACTION METHANOL (f)


Figure 4-22. Relative sorption coefficient (KM/Kw) as a function of fraction of methanol (f) for
DDT sorption by soils.


Figure 4-23. DDT Koc values from different soils


DDT Soil K oc


250000


200000


150000


Koc100000

50000


0


Perrine Chekika Krome Monteocha Lauderhill

SOIL


-


-


-











Sorption Coefficent of DDT Normalized with OC
Koc = 195665 19668; R2 = 0.9898
80000


C.) 60000


0
40000 Data
S- Linear (Data)

20000
o0


0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
ORGANIC CARBON CONTENT (OC, g/g)

Figure 4-24. Relationship between the sorption coefficient (Kw) and soil organic carbon content
(OC) for sorption ofDDT by soils.









CHAPTER 5
CONCLUSIONS

Sorption on container walls (Teflon, glass, and polycarbonate) by strongly hydrophobic

organic chemicals (SHOCs) was observed in this study. This experimental error plays a

significant role in reducing analyte integrity before the actual sample concentration is measured

by HPLC or TLC in aqueous systems. This is mainly due to the very low aqueous solubility of

these chemicals. This research also alerts manufacturers of containers that all containers tested

adsorb SHOCs during storage and multi-step analysis in aqueous systems.

Based on this research, storing Dieldrin and DDT dissolved in water for 24 hours in

Teflon lined centrifuge tubes gives less than 40% recovery of original concentrations of dieldrin

and DDT. Soil sorption isotherms therefore should be done in mixed solvents for example

methanol and water that eliminate sorption on containers.

DDT sorbs more than dieldrin on Teflon lined centrifuge tubes in aqueous systems.

Samples of SHOCs when put in HPLC glass vials before HPLC analysis are subject to

adsorption on glass walls. This phenomenon was clearly demonstrated by sorption of dieldrin on

HPLC vials. HPLC vials sorb more dieldrin than Teflon lined centrifuge tubes.

Reasonable values of cosolvency powers and hydrocarbonaceous surface areas of

strongly hydrophobic organic chemicals can be calculated by fitting data for sorption on

container walls and by soils using the Solvophobic model since cosolvency powers of these

chemicals are independent of the sorbents.

The Koc values obtained in this study using mixed solvent system and thus eliminating

sorption on container walls varied much less than those reported in the literature for dieldrin and

DDT. This implies that sorption on container walls plays a significant role in the variability of

the literature Koc values. It also shows that the Solvophobic model can be used to calculate the









aqueous sorption coefficient by extrapolating to zero fraction of cosolvent (methanol). However,

Koc values of carbonatic soils seem to be lower than values from non-carbonatic soil. This was

attributed to the source and nature of organic matter in carbonatic soils that might be different

from that of non-carbonatic soils.

Generally sorption of DDT, anthracene, and dieldrin was directly proportional to soil

organic carbon content. The trend of sorption of the chemicals on the soil s was in the same order

as their aqueous solubilities (DDT > Anthracene > Dieldrin). The trend agrees with the literature

data.

Although sorption of the chemicals on organic carbon is only examined, sorption on other

soil components like clays and carbonates should be investigated in future research. This study

has shown high Koc values for Krome (OC = 1%) compared to organic soil, Lauderhill (OC =

31%) which emphasizes the argument that there could be other soil components sorbing SHOCs.

Further examination of the hydrophobicity of the organic carbon of the carbonatic soils is

needed. For example this study has consistently shown that sorption coefficients values (Koc) of

Krome (OC = 1%) are higher than those of Perrine (OC = 3%) yet this would be the opposite

according to literature data.









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BIOGRAPHICAL SKETCH

Augustine Muwamba is a Ugandan by nationality who was born on July 10, 1980. He got

his undergraduate degree (B.S. in Agriculture) in 2005 from Makerere University, Kampala,

Uganda. He immediately started his MS in fall 2005 at University of Florida and got his MS

degree in Soil and Water Science in fall 2007. He will start his PhD program in spring 2008 in

the Soil and Water Science Department at the University of Florida.





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1 DETERMINATION OF AQUEOUS SOIL SORPTION COEFFICIENT (Koc) OF STRONGLY HYDROPHOBIC ORGANIC CHEMICALS (SHOCs) USING MIXED SOLVENT SYSTEMS AND THE SOLVOPHOBIC MODE L By AUGUSTINE MUWAMBA A THESIS PRESENTED TO THE GRADUATE SCHOO L OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007

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2 2007 Augustine Muwamba

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3 To my Mom and Dad. Thanks go to them for their encouragement and interest in my ed ucation since first grade.

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4 ACKNOWLEDGMENTS I would like to thank my advisor, Dr Peter Nkedi Kizza, for his guidance, encouragement support, and patience through out this work. A lot of encourangement from him made this research a success. I would l ike to thank Dr R oy D. Rhue and Dr. Jeffrey J. Keaff a ber for all their technical support, patience and advising me whenever I needed help. Thanks also go to Dr W. Harris, Dr L.T. Ou and Dr. J. Thomas for allowing me to use their laboratories. Thanks go to the lab manager s Mr. K Awuma and Mr. B. Querns for the ir technical support through out this work.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .................... 4 LIST OF TABLES ................................ ................................ ................................ ................................ 7 LIST OF FIGURES ................................ ................................ ................................ .............................. 8 ABSTRACT ................................ ................................ ................................ ................................ ........ 10 CHAPTER 1 INTRODUCTIO N ................................ ................................ ................................ ....................... 12 Hypotheses ................................ ................................ ................................ ................................ ... 13 Study Objectives ................................ ................................ ................................ ......................... 13 2 LITERATURE REVIEW ................................ ................................ ................................ ........... 16 Harmful Effects of Persistent Organic Pesticides (POPs) that are also (SHOCS) .................. 18 Concept of Koc ................................ ................................ ................................ ............................ 19 Variability of Koc Values in Literature for Persistent Organic Pollutants (POPs) that are also (SHOCS) ................................ ................................ ................................ .......................... 23 The Solvophobic Theory ................................ ................................ ................................ ............ 24 3 MATERIALS AND METHODS ................................ ................................ ............................... 28 Soils ................................ ................................ ................................ ................................ .............. 28 Solvents and Sorbates ................................ ................................ ................................ ................. 28 Teflon Lined Centrifuge Tubes, High Pressure Liquid Chromatography (HPLC) Glass Vials, High Pressure Liquid Chromatography (HPLC), and Liquid Scintillation Counting (LSC) ................................ ................................ ................................ ....................... 29 Sorption Experiments ................................ ................................ ................................ .................. 29 Reduced Sample Integrity Due to Sorption on container walls: ................................ ....... 29 Determination of Surface Areas of Teflon Lined Centrifuge Tubes and HPLC Glass Vials ................................ ................................ ................................ ................................ .. 30 The Solvophobic Theory ................................ ................................ ................................ ............ 30 Sorption of Persistent Organic Chemicals on Container Walls and Soils ........................ 30 endosulfan on teflon lined centrifuge tubes (TLCT) and HPLC vials (HPLCV) ................................ ................................ ................................ .......... 32 Sorption of dieldrin on HPLC vials (HPLCV) ................................ ........................... 33 Sorption of dieldrin on teflon lined centrifuge tubes (TLCT) ................................ ... 34 Sorption of anthracene on teflon lined centrifuge tubes (TLCT). ............................. 34 Sorption of DDT on Teflon lined centrifuge tubes ................................ .................... 35 Sorption Isotherms on Soils ................................ ................................ ................................ 36 Estimation of equilibrium concentrations ................................ ................................ .......... 36 Sorption of a nthracene on soils ................................ ................................ ................... 36

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6 Sorption of DDT on soils ................................ ................................ ............................. 38 Sorption of dieldrin on soils ................................ ................................ ........................ 39 4 RESULTS AND DISCUSSION ................................ ................................ ................................ 45 Sorption on Container Walls ................................ ................................ ................................ ...... 45 Sorption of 12 C endosulfan on Teflon Lined Centrifuge Tubes (TLCT) and HPLC Vials (HPLCV). ................................ ................................ ................................ ................ 45 Sorption of 12 C Dieldri n on Container Walls ................................ ................................ .... 46 Sorption on HPLC vials (HPLCV) and Teflon lined centrifuge tubes (TLCT) ....... 46 Sorption of 14 C Anthracene on Teflon Lined Centrifuge Tubes (TLCT) ........................ 47 Sorption of 14 C DDT on Teflon Lined Centrifuge Tubes (TLCT) ................................ ... 47 Conclusions ................................ ................................ ................................ ................................ 48 Sorption Isotherm Experiments ................................ ................................ ................................ .. 49 Sorption of Dieldrin on Soils ................................ ................................ .............................. 49 Sorption of Anthracene on Soils ................................ ................................ ......................... 50 Sorption of DDT on Soils ................................ ................................ ................................ .... 52 Conclusions ................................ ................................ ................................ .......................... 53 5 CONCLUSIONS ................................ ................................ ................................ ......................... 70 LIST OF REFERENCES ................................ ................................ ................................ ................... 72 BIOGRAPHICAL SKETCH ................................ ................................ ................................ ............. 76

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7 LIST OF TABLES Table page 2 2 S W K OW and K OC values from the literature for selected POPs ................................ .......... 25 2 3 Compar ison of measured and calculated K OC values in four soils ................................ ...... 26 3 1 Characteristics of the soils used ................................ ................................ ............................ 41 3 2 Some properties of the solvents (at 25 o C) used ................................ ................................ .... 41 3 3 Summary of initial and equilibrium concentrations used for sorption isotherms .............. 41 4 1 Parameters u sed to calculate chemical properties (HSA, K OC and K M ) ............................ 54 4 2 endosulfan, Anthracene and Dieldrin on containers. ......................... 54 4 3 Sorption coefficients (K W c ) and hydrocarbonaceous surface area (HSA) for Dieldrin ................................ ................................ ............................ 55 4 4 Sorption coefficients (K W c ) a nd hydrocarbonaceous surface areas (HSA) for Anthracene ................................ ................................ ..................... 55 4 5 c ) and hydrocarbonaceous surface areas (HSA) for DDT ................................ ................................ ................................ ............. 55

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8 LIST OF FIGURES Figure page 2 1 DDT :(C 14 H 9 Cl 15 (2, 2, 2 Trichloroethylidene) bis (4 chlorobenzene) ..................... 27 2 2 Dieldrin:(C 12 H 8 C l6 O)3,4,5,6,9,9 Hexachloro 1a,2,2a,3,6,6a,7,7a octahydro 2,7:3,6 dimetanonapth[2,3 b] oxirene. ................................ ................................ .............................. 27 2 3 endosulfan:6,7,8,9,10,10 hexachloro 1,5,5a,6,9,9a hexahydro 6,9 methano 2;4,3 benzadioxahepin 3 oxide. ................................ ................................ ................................ ...... 27 2 4 Anthracene: C 14 H 10 ................................ ................................ ................................ ................ 27 3 1 Sorption of a chemical up to HPLC analysis ................................ ................................ ........ 42 3 2 Sorption of a chemical up to LSC analysis ................................ ................................ ........... 42 3 3 Calculation of the area of HPLC vials covered by solution ................................ ................ 43 3 4 Calculation of the area of Teflon Lined Centrifuge Tubes covered by solution ................ 44 4 1 Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c Endosulfan by Teflon Lined Centrifuge Tubes and HPLC Vials .... 56 4 2 Percent recovery o Endosulfan sorption on Teflon Lined Centrifuge Tubes and HPLC Vials ................................ ................................ ................................ ............................. 56 4 3 Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of Dieldrin by Teflon Lined Centrifuge Tubes and HPLC Vials ............. 57 4 4 Percent recovery of Dieldrin sorption on HPLC Vials ................................ ........................ 5 7 4 5 Percent recove ry of Dieldrin sorption on Teflon Lined centrifuge Tubes (TLCT) ........... 58 4 6 Relative sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for Dieldrin sorption by Teflon Lined Ce ntrifuge Tubes and HPLC Vials. ............................. 58 4 7 Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of Anthracene by Teflon Lined Centrifuge Tubes. ................................ ... 59 4 8 Percent recovery of Anthracene sorption on Teflon Lined centrifuge Tubes .................... 59 4 9 Log linear relationship between sorption coeff icient (K M ) and fraction of methanol (f c ) for sorption of DDT by Teflon Lined Centrifuge Tubes ................................ ............... 60 4 10 Percent Recoveries of Dieldrin sorption on Teflon Lined Centrifuge Tubes ..................... 60

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9 4 11 Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of Dieldrin by soils ................................ ................................ ...................... 61 4 12 Relati ve sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for Dieldrin sorption by soils. ................................ ................................ ................................ ...... 61 4 13 Dieldrin K OC from different soils ................................ ................................ .......................... 62 4 14 Relationship between the sorption coefficient (K W ) and soil organic carbon content (OC) for sorption of Dieldrin by soils ................................ ................................ ................... 62 4 15 Log linear relationship between s orption coefficient (K M ) and fraction of methanol (f c ) for sorption of Anthracene by Krome soil. ................................ ................................ .... 63 4 16 Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of Anthracene by soils ................................ ................................ ................ 64 4 17 Relative sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for Anthracene sorption by soils. ................................ ................................ ................................ 65 4 18 Anthracene K OC values from different soils ................................ ................................ ......... 66 4 19 Relationship between the sorption coefficient (K W ) and soil organic carbon content (OC) for sorption of Anthracene by soils ................................ ................................ ............. 66 4 20 Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of DDT by Krome soil. ................................ ................................ ............... 67 4 21 Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of DDT by soils. ................................ ................................ .......................... 67 4 22 Relative sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for DDT sorption by soils. ................................ ................................ ................................ ........... 68 4 23 DDT K OC values from different soils ................................ ................................ .................... 68 4 24 Relationship between the sorption coefficient (K W ) and soil organic carbon content (OC) for sorption of DDT by soils. ................................ ................................ ....................... 69

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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 DETERMINATION OF AQUEOUS SOIL SORPTION COEFFICIENT (K OC ) OF STRONGLY HYDROPHOBIC ORGANIC CHEMICALS (SHOCs) USING MIXED SOLVENT SYSTEMS AND THE SOLVOPHOBIC MODEL By August ine Muwamba December 2007 Chair: Prof. Peter Nkedi Kizza Major: Soil and Water Science Determination of the sorption coefficients (Koc) of strongly hydrophobic organic chemicals (SHOCs) in aqueous systems is difficult due to their very low solubility and the potential to adsorb on container walls and vessels. e ndosulfan, d ieldrin, DDT, and a nthracene endosulfan on T eflon l ined c entrifuge t ubes (TLCT) and HPLC v ials (HPLCV) was measured in methanol water systems. Similarly, DDT and a nthrace ne sorption on TLCT was also measured. The volume fraction of methanol (f c ) ranged from 0.01 to 1. The solution concentrations of 12 C d ieldrin and 12 C endosulfan were analyzed using h igh p ressure l iquid c hromatography (HPLC) with UV detection. Liquid s ci ntillatio n counting (LSC) was used to measure solution concentrations of 14 C DDT and 14 C a nthracene. The container sorption coefficients (K W ) in aqueous systems were obtained by use of the S olvophobic model and extrapolating the sorption coefficient to ze ro fraction cosolvent ( f c = 0). Using the S olvophobic model endosulfan due to sorption on TLCT an d HPLCV in aqueous system was 30 %. Dieldrin recovery at f c = 0 was 6 and 32% from HPLCV and TLCT, respectively. DDT adsorbed most on TLCT followed by d ieldrin and least

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11 a nthracene, with calculated recoveries in aqueous system of 29, 32, and 52%, respectively. Negligible adsorption was detected for d ieldrin at f c 0.45 i n TLCT and at f c 0.70 in HPLCV. Similarly negligible adsorption was detected for DDT and a nthracene at f c 0.45 in TLCT. It is important to point out that most researchers assume that T eflon lined centrifuge tubes and HPLC vials do not adsorb organic chemicals The sorption coefficients of d ieldrin, DDT, and a nthracene by 3 carbonatic soils, one organic soil, and o ne s podosol were then determined in methanol water systems that eliminated sorption on the TLCT and HPLCV. The soil sorption coefficients (K W ) in aqueous systems were extrapolated at volume fraction methanol (f c = 0). The K W values were then normalized w ith soil organic carbon content (OC) to obtain [K OC = K M /OC] values. The K OC values for DDT, d ieldrin, and a nthracene obtained in this study were much lower than literature values and did not drastically vary across soil as it is reported in the literature The K OC values for d ieldrin obtained in this study varied within a factor of 2 compared to the literature factor of 4. For DDT the K OC values varied within a factor of 4 compared to the reported literature factor of 13. The K OC data from this study str ongly indicate that sorption on container walls if neglected is a potential source of error while determining adsorption of strongly hydrophobic chemicals in aqueous systems. It is therefore recommended that sorption experiments of strongly hydrophobic che micals be carried out in TLCT above 45% cosolvent in a mixture with water and at and above 70% cosolvent in HPLC vials The sorption coefficients in aqueous systems can then be calculated using the S olvophobic model eliminating errors due to sorption on co ntainer walls and over estimation of sorption coefficients The hydrocarbonaceous surface area (HSA) of SHOCs calculated from sorption on TLCT, HPLCV, and by soils gave similar values as predicted by the S olvophobic theory

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12 CHAPTER 1 INTRODUCTION Experi mental determination of soil sorption coefficients (Koc) values of strongly hydrophobic organic chemicals (SHOCs) has been traditionally done in aqueous systems assuming that there is no sorption on container walls and vessels. This might ha ve led to a lot of varia bility in literature data reported on Koc of strongl y hydrophobic organic chemicals. Although there are other losses through evaporation of volatile compounds(physical processes), photolysis, oxidation, reduction and complexing (chemical reaction s) and biodegradation (Namiesnik et al., 2002; Namiesnik et al., 2000), adsorption of these chemicals on container walls plays a significant role in variability of literature Koc values (Lung et al., 2000) Strongly hydrophobic organic chemicals have l ow water solubility (Sw) of less than 10 5 5 6 (Pontolillo and Eganhouse, 2001) and log Koc values > 4 (Karichkoff, 1981). More than 700 publications from 1944 to 2001 for DDT and DDE, aqueous solubility and Kow values revealed a variation of up to 4 orders of magnitude (Pontolillo and Eganhouse, 2001). This variability in the literature has been observed also for other persistent organic pollutants ( POPs ), (Table2 2). Based on The Stockholm Convention (2002), 9 of the 12 p ersis tent o rganic p ollutants are pesticides (Table 1 1). These pesticides can also be classified as SHOCs. POPs are typically water hating and fat loving chemicals (i.e. hydrophobic and lipophilic) and are persistent in the environment having long half lives in soils, sediments, air or biota. In soil/sediment, a POP could have a half life of years or decades and several days in the atmosphere (Jones et al., 1999). POPs have become ubiquitous in nature. Use of S olvophobic theory has helped in prediction of sorpti on of hydrophobic organic compounds by soils and sediments. The model stipulates that the sorption of neutral hydrophobic

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13 organic chemicals decreases exponentially as the cosolvent fraction increases (Rao et al., 1985). Extrapolating sorption coefficient a t zero cosolvent in mixed solvents determines sorption of strongly hydrophobic organic pesticides in aqueous systems (Nkedi Kizza et al., 1985). A range of volume fraction of methanol ( f c ) in water where there was no sorption of a nth endosul fan, and dieldrin on T eflon lined centrifuge t ubes (T LCT) and HPLC vials was determined. Above that range of methanol, sorption coefficients (Koc) of anthracene, d ieldrin and DDT were determined using five soil series (Chekika, Perrine, Krome, Monteocha, a nd Lauderhill). Anthracene was used as a reference compound because it has no functional group s and its total surface area (TSA) is equal to the hydro carbonaceous surface area (HSA). Dieldrin and DDT are among the strongly hydrophobic organic pesticides (SHOPs) and are also endosulfan is a strongly hydrophobic organic pesticide that has been detected in canals in South Dade County, Florida (Zhough et al., 2003). Hypotheses 1. Strongly hydrophobic organic chemicals (SHOCs) adsorb on container walls and vessels during determination of Koc values in aqueous systems. 2. Mixed solvent systems can eliminate sorption of strongly hydrophobic organic chemicals on container walls and vessels. 3. The S olvophobic model can be used to calculate aqueous Koc of strongly hydrophobic organic chemicals by using sorption coefficients measured in mixed solvent systems where there is no sorption on container walls. 4. Sorption data of SHOCs on container walls and by soi ls can be used to calculate the hydrocarbonaceous surface area (HSA) of SHOCs. Study Objectives 1. Determine the range of mixed solvents ( water plus methanol ) in which sorption on container walls is eliminated for selected strongly hydrophobic chemicals (SHOCS) that include persistent organic pollutants (POPs).

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14 2. Measure sorption coefficients (K M ) values in mixed solvents for SHOCs and extrapolate the sorption coefficients (K W ) in aqueous systems using the Solvophobic model. Normalize K W values with soil organic carbon content (OC) to calculate [K OC = K W /OC] values of selected SHOCs 3. Compar e K oc values obtained in this study to literature values for various SHOCS used in this research

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15 Table 1 1. The dirty dozen : Persisten t Organic Pollutants (POPs) Pesticide s Aldrin, DDT, Dieldrin, Endrin, Heptachlor, Hexachlorobenzene, Chlordan, Mirex, Toxaphene Industrial chemical by products Polychlorinated biphenyls(PCBs) Poly chlorinated dibenzo p dioxins(Dioxins) and Furans The S tockholm Convention (2001)

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16 CHAPTER 2 LITERATURE REVIEW Varia bility in literature data for aqueous sorption coefficients (Koc) of strongly hydrophobic organic pesticides (Table2 2) can partly be attributed to losses (source of error) that occur while cond ucting experiments for Koc determination and partly to variability (Karapanagioti et al., 2000) in the source and nature of soil organic matter Losses occur through; adsorption of chemicals on the walls of samplers and vessels, evaporation of volatile com pounds (physical processes), photolysis, oxidation, reduction and complexing(chemical reactions) and biodegradation (Namiesnik et al., 2002, Namiesnik et al., 2000). Sorption on container walls plays a significant role in variability of Koc literature dat a (Manoli et al., 1999, Baltussen et al., 1998) Several researchers have shown that 40 80% of the poly chlorinated biphenyls (PCBs) in a sample may be adsorbed on to the poly tetrafluoroethylene (PTFE) surface (Baltussen et al., 1999, Lung et al., 2000). Glass containers may be responsible for a 10 25% drop in water sample content of polychlorinated biphenyls (PCBs) and poly aromatic hydrocarbons (PAHs) causing drops in analyte concentration (Manoli et al., 1999, Baltussen et al., 1998) Nine of the 12 c hemicals which belong to the class of most hazardous environmental pollutants enlisted as persistent organic pollutants (POPs) under the Stockholm Convention (2001) are pesticides. These POPs are also strongly hydrophobic organic chemicals (SHOCs). POPs ar e typically water hating and fat loving chemicals (i.e. hydrophobic and lipophilic) and are persistent in the environment having long half lives in soils, sediments, air or biota. In soil/sediment, a POP could have a half life of years or decades and sever al days in the atmosphere (Jones et al., 1999).

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17 According to Webster et al. (1998), persistence in the environment is defined operationally from a model calculated overall residence time at steady state in a multimedia environment. In aquatic systems and soils, POPs partition strongly to solids, mainly organic matter, avoiding aqueous phase. They also partition in to lipids in organisms rather than entering the aqueous milieu of cells and become stored in fatty tissue. This leads to their accumulation in f ood chains since their metabolism in biota is slow. POPs have a potential to enter the atmosphere through volatilization from soils, vegetation and water because of their resistance to breakdown reactions in air, they travel long distances before being red eposited (Ritter et al., 1995). Repeated volatilization and deposition leads to their accumulation in areas far removed from where they were used or emitted. An important class of persistent organic pesticide is the organo chlorine pesticides like DDT, ald rin, endrin, dieldrin, hexachlorobenzene, heptachlor, mirex, chlorodan e and toxaphene (Table 1 1) Some POPs are accidental byproducts of combustion or the industrial synthesis of other chemicals for example polychlorinated biphenyls (PCBs), dibenzo p diox ins ( D ioxins), chlorinated paraffins, and dibenzo p furans ( F uran s) (Ritter et al., 1995). The properties of unusual persistence and semi volatility, coupled with other characteristics, have resulted in the presence of compounds such as PCBs all over th e world, even in regions where they have never been used. They have become ubiquitous in nature. They have been measured on every continent, at sites representing every major climatic zone and geographic sector throughout the world (Ritter et al., 1995). T hese include remote regions such as the open oceans, the deserts, the arctic and the A ntarctic, where no significant local sources exist and the only reasonable explanation for their presence is long range transport from other parts of the globe. Some POPs have been reported in air, in all areas of the world, at

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18 concentrations up to 15ng/m 3 ; in industrialized areas, concentrations may be several orders of magnitude greater. POPs have also been reported in rain and snow (Ritter et al., 1995) Properties of DD T (Fig. 2 1) d ieldrin (Fig. 2 2 ), endosulfan (Figure 2 3) and a nthracene ( Fig. 2 4 ) are shown in table 2 1. Anthracene wa s used to show the validity of S o lvophobic model. It served as an id eal sorbate for evaluating the S olvophobic theory because it s s orption is characterized by S olvophobic interactions (hydro carbonaceous surface area (HSA) is equal to total surface a rea (TSA 202 2 ). Harmful Effects of Persistent Organic Pesticides (POPs) that are also (SHOCS) The concern of POPs concentrates around their impact on top predator species, humans inclusive. Clear evidence of their effects is in birds and marine mammals. In great lakes (Giesy et al., 1994) and in Europe (Bosveld and Van den Berg, 1994), numerous subtle but far reaching effects on the repr oductive potential of fish eating birds are reported. POP residues have increased in some top predators for instance harbor seals in the Southeast North Sea (Reijnders et al., 1997 ), white tailed eagles in the B alti c and p iscivorous birds in the g reat lak es (Munro et al., 1994). POPs, principally PCBs, have also been reported to cause reproductive impairment and this has been shown in seals in the B altic s ea (Bergman and Olsson, 1985) and the Dutch Wadden Sea (Reijnders, 1986) and in b el uga whales in the St. Lawrence s ea way, Canada (Beland et al. 1993). In addition to being carcinogens, POPs are among the chemicals responsible for sex hormone or endocrine disruption in humans and wild life (Harrison et al, 1995; Kavlock et al., 1996). DDE a metabolic br eak down product of DDT affects egg shell thickness (thinning) in

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19 exposure to DDT lies in taking contaminated food including maternal milk. Long term exposure leads to chronic illness and breast cancer risk. Toxicity of DDT spreads to fish too. 50% of initial amounts of DDT are found in s oil, even 10 15 years after use ( Smith 1991). Man is exposed to dieldrin through eating contaminated fish and shell fish. Infants are exposed from breast milk. Dieldrin decreases the effectiveness of our immune system, cause cancer, increase infant mortality, reduces reproductive success, causes birth defects and damages the kidneys (Smith 1991 ). endosulfan are not cleary understood however excess levels of endosulfan are toxic to both humans and animals ( Smith 1991). Concept of Koc The soil sorption coefficient (Koc) is the ratio between the concentrations of a given chemica l sorbed by the soil and that dissolved in the soil water normalized to the total organic carbon content of the soil. It is used to quantify soil sorption and the advantage of this is that Koc for a particular pesticide is assumed to be independent of the soil pesticide combination (Nkedi Kizza et al., 1983, Rao and Davidson 1980). Sorption is among the major processes that affect the fate of pesticides in the soil environment. It also regulates the rates and magnitudes of other processes that govern the fa te and transport of organic contaminants in soils and sediments. Sorption of pesticides decreases their biological activities and rates of biological degradation. However, d ue to surface cataly z ed hydrolysis, sorption may enhance non biological degradation (Stevenson, 1994). Adsorption of hydrophobic organic pollutants by soil is strongly dependent on the soil organic matter content (Means et al., 1980; Xing et al., 1994). Organic matter can be humic or nonhumic (Morrill et al., 1982) and humified material is often a stronger sorbent for non ionic pesticides due to the presence of oxygen containing functional groups like COOH, phenolic, aliphatic, enolic, OH, and C=O. However this is not true for ionic pesticides, due to the range

PAGE 20

20 of possible sorption me chanisms (Hance, 1988). The chemistry of soil organic matter in soils from different geographical regions varies. Soil organic matter may vary from soil to soil in its polarity, elemental composition, aromaticity, condensation, and degree of diagenetic evo lution from a loose polymer to condensed coal like structures (Garbarini and Lion, 1986; Gauthier et al., 1987; Grathwohl, 1990; Karapanagioti et al., 2000). Therefore land variations, such as type and age of soil organic matter may affect sorption of non ionic pesticides. Three different processes; film diffusion, retarded intra particle diffusion and intrasorbent diffusion, that involve diffusion mass transfer cause sorption related nonequilibrium. Retarded intraparticle diffusion is aqueous phase diffus ion of solute within pores of micro porous particles; forexample, sand grains mediated by retardation resulting from instantaneous sorption to pore walls. Intra sorbent (intra organic matter) diffusion involves the diffusive mass transfer of sorbate with i n the matrix of the sorbent. It involves diffusion within organic matter matrix. The major assumption in intra organic matter diffusion model is that sorbet organic matter is a polymeric type substance within which sorbate can diffuse. The organic matter a ssociated with natural sorbents is reported to be a flexible, cross linked, branched, amorphous (noncrystalline), polyelectrolytic polymeric substance (Brusseau et al., 1991). The amount of chemical adsorbed is a function of both the s oil and the solute. The distribution coefficient or partition coefficient, K W ( L / k g ), is estimated by K W = f oc Koc where f oc is a function of the s oil and is the fraction of naturally occurring organic carbon measured in the soil and K W is a function of the solute and is the partition coefficient of the solute between water and organic carbon. A linear model of the following form is employed to approximate sorption data for soils and sediments.

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21 S e = K W C e 2 1 Where S e ( mg / k g) is the mass of s olute sorbed per unit mass of solid at equilibrium, C e ( mg / L ) is solute concentration and K W ( L / k g ) is the distribution coefficient in aqueous systems The parameter, octanol water partitioning coefficient (K OW ) which is the measure of hydrophobicity (wate r repulsing) of an organic compound (solute) is given by: K OW = C O /C W 2 2 Where C O ( m g/ L ) is the concentration in the octanol phase and C W ( mg / L ) is the concentration in aqueous phase. Kow is used in assessment of environmental fate and transport for organic chemicals because the octanol phase is a surrogate for the lipid phase or organic carbon content of environmental compartments. K OW is correlated to water solubility, soil/sediment adsorption coefficients, and bioconcentration factors for aquatic life (Lyman et al., 1990) and this makes it a key variable in estimation of these variables. The less hydrophobic (small K OW ) a compound is, the more soluble it is in water and less likely it will adsorb to soil particles (Bedient, 1994). Several relations have been developed between K OC and K OW : Log K OC = a log K OW + b 2 3 Values reported for a and b in Eq. 2 3 include (a = 1 and b = 0.48) for polycyclic aromatic hydrocarbons, (a = 0.52 and b = 4.4) for certain group of pesticides and (a = 0.72 and b = 3.2) for alkylated and chlorinated benzenes (Jones and de Voogt, 1999). Conclusion from the available data is that, values of a and b are determined by the type of compounds that is compound classes and range of liphophilicity on which the relationship is established and only to a smaller degree by the type of natural sorbents used (Jones and de Voogt, 1999). According to Karickhoff et al. (1981), the following relationship was found; Log K OC = 0.989 log K OW 0.346 (5PAHs, r 2 = 0.997) 2 4

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22 Equation 5 was for 13 methylated and halogenated benzenes (Schwarzenbach and Westall, 1981) Log K OC = 0.72 log K OW + 0.49 (r 2 =0.95) 2 5 affinities for octanol and natural organic matter. After arranging hydrocarbons into homologous groups, they came up with the following relation ships: Log K OC = 0. 774 log K OW + 0.37 (alkylnaphthalenes, r 2 =0.992) 2 6 Log K OC = 1.20 log K OW 1.13 (4 PAHs, r 2 = 0.998) 2 7 Log K OC = 0.904 log K OW 0.46(alkyl benzenes, r 2 = 0.992) 2 8 Chiou (1990) reported a relationship between K OM and K OW for sorption of vari ous organic compounds, including several pesticides, by different soils and sediments as; Log K OM = 0.94 log K OW 0.779 (r 2 =0.989) 2 9 W here K OM is the partition coefficient for the organic compound between soil organic phase (based on organic matter ) and water. There are propositions that solubility relationships for aliphatic and aromatic solutes are ml et et al.,1987) and additions of ring fragments and functional group s on the aromatic ring (Karickhoff,1985). Experimental determination of Koc values is difficult, costly and time consuming. For (Chiou et al., 1979; Kenaga and Goring, 1 980). Therefore, correlations between K OC and K OW listed in Eqs. 2 3 to 2 9 might be question able due to experimental errors made when measuring K OC values in aqueous systems for strongly hydrophobic organic chemicals (SHOC s )

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23 Vari a bility of Koc Values in Literature for Persistent Organic Pollutants (POPs) that are also (SHOCS) Recently research scientists have questioned the reliability of chemical property data in the literature especially for SHOCs (Pontolillo and Eganhouse, 2001). Since this class of c hemicals is sparingly soluble in water, direct determination of S W K OW and K OC is problematic. Therefore indirect estimation based on correlations between S W K OW or K OC with measurable molecular parameters (connectivity indices, HPLC capacity factors etc ) have been used in the literature (Sangster, 1997, Karichkoff, 1981). However, these techniques depend on various assumptions that produce results that are not always comparable ((Pontolillo and Eganhouse, 2001). A literature search from 700 publications from 1944 to 2001 for DDT and DDE, S W and K OW values revealed a variation of up to 4 orders of magnitude (Pontolillo and Eganhouse, 2001). This trend in parameter variability in the literature is true for other POPs (Table 2 2 ). Environmental risk asses sment, fate and transport models, and sediment quality guidelines may not be accurate because of the variability of basic data needed to predict the fate of contaminants (POPs) in the environment (Renner, 2002). This problem is clearly demonstrated in Tabl e 2 1. For example the K OC values for d ieldrin vary within a factor of 4 and for DDT the K OC values vary within a factor of 13. Karichkoff (1981) reported K OC values for weakly hydrophobic chemicals (K OC < 1000) to vary within a factor of 2. The variatio n in the literature values of the three parameters (K OW K OC and S W ) for SHOCs has been attributed to measurement uncertainty due to different analytical methods, temperature differences, lack of equilibrium and impurities of test compounds (Linkov et al ., 2005; Chiou et al., 2005). However, one process that damages sample integrity before analysis is analyte adsorption onto the walls of samplers and vessels. This process has been ignored in the literature especially for SHOCs. Wolska et al. (2005) report ed up to 70% of adsorption of PAHs and PCBs on walls of containers.

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24 The adsorption on walls of containers increased as log K OW of the chemicals increased from 6.5 to 8.5 The Solvophobic Theory Rao et al., (1985) and Nkedi Kizza et al., (1985) showed that the S olvophobic model can be used to estimate (in aqueous systems) the sorption coefficient normalized to soil organic carbon content (K OC ) of hydrophobic organic chemicals. Nkedi kizza et al., (1985) suggested that sorption of SHOCs in aqueous systems can be determined in mixed solvents by extrapolating K OC at zero co solvent. Data for one SHOC (Anthracene) and two pesticides (Atrazine and Diuron) were presented that showed the validity of the S olvophobic model (Table 2 3 ).

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25 Table 2 1. Properties of the ch emicals used in the study Property Chemical DDT Dieldrin endosulfan Anthracene Melting point( o C) 108.5 175 176 70 100 217 Aqueous solubility at 25 o 1.2 5 140 320 75 Log K OC 5 15 6.26 4.08 4.55 4.06 4.22 Boiling point( o C) 260 385 106 340 Appearance White powder White crystals Colorless crystals Yellow cryastals Source: Nkedi Kizza et al., 1985; Kidd et al ., 1991. Table 2 2 S W K OW and K OC values from the literature for selected POPs Pesticide *Log K OW K OW Source Aldrin 5.17 to 7.40 147,910 to 25,118,864 a DDT 4.89 to 6.91 77,624 to 8,128,305 a and b Dieldrin 3.69 to 6.20 4,897 to 1,584,893 a HCB 3.03 to 6.42 1,071 to 2,630,267 a Pesticide *Log K OC K OC Aldrin 2.61 to 4.69 407 to 48,978 a Chlordane 4.58 to 5.57 38,019 to 371,535 a DDT 5.14 to 6.26 138,038 to 1,819,701 a Dieldrin 4.08 to 4.55 12,023 to 35,481 a HCB 2.56 to 4.56 363 to 36,308 a Pesticide *S W Temperature ( 0 C) Aldrin 17 to 180 25 a DDT 1.2 to 5.5 25 a Endrin 220 to 260 25 a Source: a. Ritter et al., 1995; b. Pontolillo and Eganhouse, 2001

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26 Table 2 3. Comparison of measured and calculated KOC val ues in four soils Sorbate Literature K OC Measured K OC in water (f c =0) Measured K OC in methanol water. Calculated with Solvophobic model Measured K OC in acetone water. Calculated with Solvophobic model Anthracene 15849 16032 16560 16912 Atrazine 146 96 90 89 Diuron 426 426 417 351 Source: Nkedi Kizza et al., 1985

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27 Figure2-1.DDT :(C14H9Cl15)1, 1-(2, 2, 2-Trichloroethylidene) bis (4-chlorobenzene) Figure2-2.Dieldrin:(C12H8Cl6O)3,4,5,6,9,9-Hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6dimetanonapth[2,3-b] oxirene. Figure2-3. -endosulfan:6,7,8,9,10,10-hexachloro-1,5,5a,6,9, 9a-hexahydro-6,9-methano-2;4,3benzadioxahepin 3-oxide. Figure 2-4. Anthracene: C14H10

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28 CHAPTER 3 MATERIALS AND METHOD S Soils Five soil s were used of which three were carbonatic (Perrine, Chekika and Krome) and two non carbonatic (Lauderhill, organic) and (Monteocha, Spodosol). The so ils were taken from 0 15 cm of top soil. The Spodosols were collected from Alachua County, Florida. Carbonatic soils are defined as soils containing 40% carbonates (calcite and/or dolomite). The carbonatic soils in South Florida are classified as Entisols and the associated organic soils (Histosols) are mainly saprists and fibrists (NRCS, 1987). Organic soils are defined as soils containing a minimum of 12% organic carbon when the mineral portion contains no clay or 18 % organic carbon if the soil has 60% o r more clay (Lucas, 1982).The soils were selected to represent different geographical conditions and organic matter content. The soil series are presented in Table 3 1. The organic carbon content of the soils was determined by the dichromate method (Walkle y and Black, 1934). Solvents and Sorbates The binary solvents used in this study were various mixtures of methanol and 0.01MCaCl 2 Methanol was chosen to represent an organic cosolvent that is completely miscible with water. The properties of the solvent s are shown in Tables 3 2. Anthracene was selected to represent an ideal strongly hydrophobic organic chemical ( sorbate ) without any polar functional groups. Its total surface area (TSA) is equal to hydrocarbonaceous surface area (HSA). Radio labeled 14 C anthracene was used as a tracer for 12 C anthracene. Dieldrin, endosulfan, and DDT are strongly hydrophobic organic chemicals (SHOCs). Radio labeled 14 C DDT was used as a tracer for 12 C endosulfan

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29 m ethanol, and water all of HPLC grade w ere obtained from Fisher Scientific. All chemicals were of 99.9% purity Teflon L ined Centrifuge T ubes, H igh Pressure Liquid Chromatography (HPLC) Glass V ials, High Pressure Liquid Chromatography (HPLC), and Liquid Scintillation Counting (LSC) Teflon line d centrifuge tubes are widely used in many experiments. They are made up of a polymer called poly tetraflo u roethylene (PTFE). The tubes were obtained from Fisher scientific. Before samples are analyzed by HPLC UV, they are first put in HPLC vials and then put in autosampler for injection. They are made up of borosilicate (glass). The vials were bought from Fisher scientific. The HPLC system consisted of a pump: SP8800, an Intergrator: Dionex4270 Detector : Waters 490 programmable multivalent detector, and Autosampler: SP8780. Column: Nova Pak C18. The Liquid scintillation counter (Beckman LS 100 C model) was used to determine the 14 C activity in 1 mL aliquots of solutions added to (Scinti Verse II scintilla tion liquid, Fisher Scientific). Sorption E xperimen ts Before conducting sorption experiments, the following were put in to consideration. Reduced Sample Integrity Due to Sorption on container walls: The three possible steps where a chemical is sorbed before HPLC analysis when working in aqueous systems are : 1. Preparation of a stock solution in containers 2. Transfer of solution with plastic pipette to centrifuge tubes 3. Transfer of solution with plastic pipette to HP LC v ials after centrifugation. These three steps are illustrated in Fig. 3 1.

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30 These so urces of errors also occur when using LSC (Fig. 3 2). Unlike in HPLC analysis where some of its parts can sorb the chemical, LSC parts are excluded in the LSC analysis. The solution sample to be analyzed is directly added to the scintillation liquid which is a mixture of organic solvents. The possible error is due to the pipette used to transfer the solution. All the stock solutions of the chemicals that were used in this research were prepared in pure methanol to eliminate sorption on the containers. Pipe tte tips were first rinsed with 1 mL methanol before being used in any step of the procedure. For the LSC analysis, after the sample had been transferred into the scintillation vial the pipette was rinsed with 1 mL of the scintillation liquid and then add ed to the scintillation vial. Determination of Surface Areas of Teflon Lined Centrifuge Tubes and HPLC Glass V ials Since 1 mL of solution was added to square flat bottom HPLC vials when analyzing solutions from sorption experiments, the area of the HPLC via ls covered by the solution was calculated. It was calculated to be 4.76 cm 2 using the dimensions of the vial (Fig. 3 3). The area of the Teflon Lined Centrifuge tube covered by the solution was calculated by a scanning model (Rhinoceros 3D SR410, 2006) Th e area of the tube covered by 10 mL of the solution was calculated to be 38.5 cm 2 (Fig. 3 4). The Solvophobic Theory Solvophobic theory was used to carry out the following; Sorption of Persistent Organic Chemicals on Container Walls and S oils During batch sorption experiments the main processes that would damage sample integrity would include sorbate adsorption on the walls of samplers, vessels, tubing, components of the pump, and injector valves; chemical reactions (photolysis, oxidation, reduction, and c omplexing) and biodegradation. To reduce sorbate loss before analysis, steps were taken to analyze the samples quickly. Also working in mixed solvents would reduce sorption on container walls. In

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31 mixed solvents, biological degradation is also reduced due to microbial toxicity of the organic solvents. For sorption of SHOCs on container walls, the following equatio ns were developed based on the S olvophobic model in Eq. 3 1 (Rao et al., 1985 ; Nkedi Kizza et al., 1985) K M = K W exp ( c c f c ) 3 1 R M = C e /C o 3 2 S e = V/A (C o C e ) 3 3 K M = S e /C e = V/A (C o /C e 1) 3 4 K M = V/A (1/R M 1); K W = V/A (1/R W 1) 3 5 R M = 1/ (1 + (A/V) K W exp ( c c f c ) 3 6 R W = 1/ (1+ (A/V) K W ) 3 7 Where K M and K W are sorption coefficients ( mL /cm 2 ) in co solvent and in aqueous systems, respectively; R M = fraction of chemical recovered at each f c ; C e = equilibrium solution concentration ( mL ); C o = initial solution concentration mL ); S e = adsorbed concentration 2 ); V = volume of solution added to the tube ( mL ); A (cm 2 ) = area of the tube covered by volume V; R W and R M = fraction of chemical recovered in water and mixed solvents, respectively. Eq uation 3 1 can be used to calculate K W at f c = 0 and Eq. 3 6 to calculate R W also at f c = 0. The sorption on container walls was carried out as one point isotherm in triplicate. c in Eqs. 3 1 and 3 6 is the cosolvency power and can also be equated to the hypothetical liquid liquid partition coefficient. Therefore it may be approximated as: c = l n [S C / S W ] 3 8 Where S C and S W are the hydrophobic chemical mole fraction solubility in neat cosolvent and water, respectively. The value of c is strongly correlated to solute properties such as

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32 octanol water partition coefficient (K OW ) and molec ular hydrophobic surface area (HSA) and to solvent properties such as dielectric constant, interfacial tension and bulk surface tension (Yalkowsky et al., 1976) c c HSA]/ (kT) 3 9 c w c (ergs/ 2 ) = difference in interfacial free ener gy at the aqueous interface and the organic co solvent interface with the hydro carbonaceous surface area (HSA, 2 ) of SHOC molecule; k (ergs/K) is Boltzmann constant ; T is temperature in K. For sorption of SHOCs on soils Eqs. 3 3 and 3 4 are modified as follows: K M = S e /C e = V/m (C o /C e 1) in mixed solvents 3 10 K W = S e /C e = V/m (C o /C e 1) in water 3 11 Where K M and K W are sorption coefficients ( L / k g) in co solvent and in aqueous systems, respectively; m = mass o f soil (kg) Other parameters have been defined earlier. K W can be estimated at f c = 0 using Eq. 3 1 and K M data obtained in the range of co solvent, where sorption on container walls is eliminated. endosulfan on t eflon l ined c entrifuge t ub es (TLCT) and HPLC v ials (HPLCV) mL endosulfan were added to 50 mL T eflon lined centrifuge tubes and volumes of 0.01M CaCl 2 solutions were added to make a total of 10 mL thus obtaining fractions of methanol (f c ) i ncreasing from 0.1 to 0.8. The range of maximum equilibrium concentration (C e ) at each f c was predetermined to be the same by varying the amount of C o added to make the 10 mL of solution. Each co solvent was prepared in triplicates. The solutions were samp led after 24 hours without shaking (batch method). A sub sample (1 mL ) of each triplicate was put in HPLC vials. The solutions were analyzed by high pressure liquid c hromatography (HPLC) with UV detection. All the standards were prepared in methanol

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33 The c onditions for HPLC were: mobile phase, 80%acetonitrile: 20%water, wavelength, 214 nm, and flow rate of 1 mL endosulfan sorption on container walls was not separately determined for TLCT and HPLC vials. The measured concentration of the aliquot was mL ). The Ce values at each f c were then used to calculate R M and K M using Eqs. 2 2 and 2 4 respectively However, the a rea of the TLCT covered by 10 mL was used in Eq. 3 4. Equations 3 1 to 3 6 and 3 9 were used to calculate prop erties of endosulfan (cosolvency power, percent of a chemical recovered from the HPLC vials plus TLCT, sorption coefficient in water, and HSA) The ratio of V/A was essentially equal for TLCT and HPLCV. Sorption of d ieldrin on HPLC v ials (HPLCV) Appropri ate volumes of d ieldrin initial concentrations of 2.5, 3.5, 4, 5, 6 and 7( mL ) were added to 0.01 M CaCl 2 soluti on in HPLC vials to make up 1 mL of solution yielding 0.25, 0.35, 0.4, and 0.5 fractions of methanol (f c ). The range of equilibrium concentrat ion (C e ) at each f c was predetermined to be the same by varying the amount of C o added to make the 10 mL of solution Each cosolvent was used in triplicates. HPLC vials of each cosolvent were prepared in triplicates. The 1 mL solution of each cosolvent was left to stand for 24 hours. Equilibrium concentration was analyzed using HPLC UV. Conditions of the HPLC were; mobile phase of 80% methanol and 20% water, wavelength of 220 nm, sensitivity of 0.04 Aufs and flow rate of 1.5 mL /min and C 18 column All the standards were prepared in methanol Samples were injected thrice in the HPLC system. Percent recoveries(R) were computed by dividing equilibrium concentration (C e ) by original concentration (C o ) then multiplying by hundred (R= (C e /C o )*100). The area cov ered with solution in HPLC vials was calculated from the vial dimensions and it was found to be 4.76 cm 2 Equations 3 1 to 3 6 and 3 9 were used to calculate properties of Dieldrin (cosolvency power, percent of a chemical recovered from the HPLC vials, sor ption coefficient in water, and HSA).

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34 Sorption of dieldrin on t eflon lined centrifuge t ubes (TLCT) Initial concentration (C o = 2 mL ), was mixed with 0.01M CaCl 2 solutions in a Teflon lined centrifuge tubes to make a total of 10 mL that yielded 0.10, 0 .20, 0.25 and 0.30 fractions of methanol (f c ). The range of equilibrium concentration (C e ) at each f c was predetermined to be the same by varying the amount of C o added to make the 10 mL of solution. Centrifuge tubes of each cosolvent were prepared in trip licates. The 10 mL solution of each cosolvent was left to stand for 24 hours. Equilibrium concentration was analyzed using HPLC UV. Conditions of the HPLC system were; wavelength of 220nm, sensitivity of 0.04Aufs, flow rate of 1.5 mL /min; mobile pha se of 80 %methanol and 20%water and C 18 column All the standards and the samples were added to HPLC v ials in methanol to make up 1 mL of at least 70% methanol. Samples were injected thrice in the HPLC system. Concentrations that were below detection limit after dilution of samples in HPLC vials with methanol were spiked with a known concentration of dieldrin in mL ). The Ce values at each f c were then used to calculate R M and K M using Eqs. 3 2 and 3 4, respectively. The area of the TLCT covered by 10 mL ( A = 38.53 cm 2 ) was used in Eq. 3 4. Equations 3 1 to 3 6 and 3 9 were u sed to calculate properties of d ieldrin (cosolvency power, percent of a chemical recovered from the TLCT, sorption coefficient in water, and HSA). So rption of anthracene on t eflon lin ed centrifuge t ubes (TLCT) A volume of 12 C Anthracene of in mL in methanol and a volume of 14 C Anthracene (10000 cpm/ mL ) also in methanol were pipetted in to 50 mL T eflon lined centrifuge tubes A volume of 0.01M CaCl 2 wa s added to make a total of 10 mL that resulted in 0.01, 0.06, 0.1, 0.20, 0.25 and 0.3 fractions of methanol. The range of equilibrium concentration (C e ) at each f c was predetermined to be the same by varying the amount of C o added to make the 10 mL of solution Each cosolvent was used in triplicates. The 10 mL solution

PAGE 35

35 wa s left to stand for 24hours. After 24 hours, equilibrium concentration was obtained by removing 1 mL of the supernatant from each cosolvent, put in a vial containing 5 mL of cocktail (Scinti Verse II scintillation solution) and analy z ed using a Beckman LS 100 C liquid scintillation counter (LSC). The analyzing time was 5 minutes. Back ground radioactivity from a blank of methanol + calcium chloride solution was subtracted from each LSC counts of the sample Equations 3 1 to 3 6 and 3 9 were used to calculat e propert ies of Anthracene (cosolvency power, percent of a chemical recovered from the Teflon lined centrifuge tubes sorption coefficient in water, and HSA). Sorption of DDT on T eflon lined centrifuge tubes A volume of 12 C DDT of initial concentration mL in methanol and a volume of 14 C DDT (10000 cpm/ mL ) also in methanol were pipetted into 50 mL Teflon lined centrifuge tubes. A volume of 0.01M CaCl 2 was added to make a total of 10 mL that resulted in 0.1, 0.2, 0.3 and 0.4 methanol fractions. T he range of equilibrium concentration (C e ) at each f c was predetermined to be the same by varying the amount of C o added to make the 10 mL of solution Each cosolvent was used in triplicates. The 10 mL solution was left to stand for 24hours. After 24 hours equilibrium concentration was obtained by removing 1 mL of the supernatant from each cosolvent, put in a vial containing 5 mL of cocktail (Scinti Verse II scintillation solution) and analyzed using a Beckman LS 100 C liquid scintillation counter (LSC). T he analyzing time was 5 minutes. Back ground radioactivity from a blank of methanol + calcium chloride solution was subtracted from each LSC counts of the sample. Equations 3 1 to 3 6 and 3 9 were used to calculate properties of DDT (cosolvency power, perc ent of a chemical recovered from the Teflon lined centrifuge tubes, sorption coefficient in water, and HSA).

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36 Sorption Isotherms on Soils Before sorption isotherm experiments were done, an experimental design was carried out to make sure that a maximum e quilibrium concentration (C e ) was maintained at all f c values and in all soils for a given chemical Estimation of e quilibrium c oncentrations All sorption isotherms from soils were designed such that equilibrium concentrations (C e ) at each f c and in each s oil were in the linear range of isotherms. This was achieved by using the Solvophobic model to calculate the solubility of each chemical at f c values from 0 to 0.7. The model was also used to estimate sorption coefficients at each f c based on literature K O C values. OC and f c values the following equations were derived: Se = K M Ce 3 12 Se = V/m (Co Ce) 3 13 Parameters in Eqs. 3 12 and 3 13 have been defined earlier. Combining Eqs. 3 12 and 3 13 yield an equation that can be used to vary the soil: solution ration at all f c values to maintain the required C e range. C e = C o / ( ( m/V*K M ) + 1) 3 14 In order to maintain the same Ce range Eq. 3 14 was used. This was achieved by adjusting C o m, an d K M depending on f c of methanol at which the isotherm was measured. A summary of the various parameters used during isotherm determination is given in Table 3 3. Sorption of a nthracene on s oils Equilibrium sorption isotherms were measured from various mix tures of methanol and water using four soils (Krome, Perrine and Chekika, and Lauderhill). Isotherms were determined in the range of methanol (f c = 0.5 to 0.7) when there was no sorption on TLCT. The soil solution

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37 ratios of 1:2, 1:1.2 5, and 1:1 were used for methanol fractions of 0.5, 0.6 and 0.7, respectively, for carbonatic soils. Initial concentrations of 12 C Anthracene were 0.1, 0.2, 0.4 mL ) for f c = 0.5, 0.6 and 0.7. The soil solution ratio at f c = 0.5, 0.6 and 0.7 were 1:1, 1:40, and 1:17, respec tively for Lauderhill. The soil solution ratios at f c = 0.5, 0.6 and 0.7 were 1:67, 1:25, and 1:13, respectively, for Monteocha. All isotherms were run in triplicates for each initial concentration and at a given f c The solutions were spiked with 14 C A nth racene to give (10,000 cpm/ mL ). Following a 24 h shaking and equilibration period, the solution phase was separated from the solid phase by centrifugation at 9000 rpm for 25 minutes and 1 mL of the supernatant was put in a 5 mL of cocktail in plastic vials Liquid scintillation counting (LSC) was used to analyze 14 C Anthracene in solution. The counting time was 5 minutes. Background radioactivity from a blank of methanol + calcium chloride solution was subtracted from counts of the sample. The decrease in s orbate solution concentration was assumed to be due to sorption by the soil. Additional sorption experiments by Krome soil were carried out at f c = 0.1, 0.2, and 0.3 with soil solution ratios of 0.01, 0.02, and 0.1, respectively. The total volume of soluti on was 10 mL All isotherms were done in triplicates. The additional data were collected to test the linearity of the S olvophobic model by directly determining a nthracene adsorbed on the soils. The initial 12 C m L ), and 14 C Anthracene was 40, 000 cpm/ mL Due to potential sorption on TLCT, the batch slurry method was modified. The amount of 14 C Anthracene adsorbed on the soil was directly determined by combusting an oven dry sub sample of the soil at the end of the equilibration period after centrifuging the samples at 9000 rpm for 25 minutes and determining C e in the supernatant solution by LSC. The soil sample was

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38 combusted in a Harvey Ox 500 Biological oxidizer, trapping the evolved CO 2 in a scintillation solutio n and quantifying 14 CO 2 by liquid scin tillation as described earlier. The adsorbed concentration (S e ) was calculated using Eq. 3 13 and was plotted against the solution concentration (C e ). The slope of the line is equal to the sorption coefficient (K M ) base d on Eq. 3 12. Equations 3 1, 3 9, and 3 10 were used to calculate properties of Anthracene (cosolvency power c ), sorption coefficient in water (K W ), and HSA. The values of K W were normalized with soil organic carbon content to calculate K OC for each soil. Sorption of DDT on s oils Methanol fractions (f c ) of 0.5, 0.55, and 0.6 were used for all soils. Initial c oncentrations of 12 C mL ) for all methanol fractions used. The soil solution ratios at f c = 0.5, 0.55 and 0.6 were 1:3, 1:2 and 1:1 respectively for Krome, Chekika and Perrine. The soil solution ratios at f c =0.5, 0.55 and 0.6 were 1:50, 1:29 and 1:20, respectively for Monteocha soil. The soil solution ratios at f c = 0.5, 0.55 and 0.6 were 1:100, 1:67 and 1:50, respectively for Lauderhill soil. The total volume of solution was 10 mL and the samples were spiked with 14 C DDT to give 40, 000 cpm/ mL Following a 24hr shaking and equilibration period, the solution phase was separated from the solid phase by centrifugation at 9000 rpm for 25 minutes and 1 mL of the supernatant was put in a 10 mL of cocktail in plastic vials Liquid scinti llation count ing (LSC) was used to analyze the solution. The analyzing time was 5 minutes. The decrease in sorbate solution concentration was assumed to be due to sorption by the soil. The adsorbed concentration (S e ) was calculated using Eq. 3 13 and was plotted against the solution concentration (C e ). The slope of the line is equal to the sorption coefficient (K M ) based on Eq. 2 12. Equations 3 1, 3 9, and 3 10 were used to calculate properties of DDT

PAGE 39

39 c ), sorption coefficient in water (K W ), and HSA). The values of K W were normalized with soil organic carbon content to calculate K OC for each soil. Sorption of d ieldrin on s oils Equilibrium so rption isotherms were measured from various mixtures of methanol and water. Methanol fractions of 0.4, 0.45, 0.5 and 0.6 were used. Soil solution ratios of 1:2.5, 1:2, 1:1.3, and 1:1 for f c = 0.4, 0.45, 0.5 and 0.6, respectively, were used for Perrine, Kro me and Chekika soils. Methanol fractions of 0.4, 0.5 and 0.6 were used for Lauderhill and Monteocha soils at solution ratios of 1:17, 1:6, and 1:3. The three initial concentrations of d ieldrin were betwee n mL The total volume of solution in TLCT was 10 mL At each f c and initial concentration, triplicate soil samples were used. Following a 24h shaking and equilibration period, the solution phase was separated from the solid phase by centrifugation at 9000 rpm for 25 minutes. The supernatant was added to HPLC vials and diluted by methanol to reach (f c = 0.7) when there was no sorption on HPLC vials. The solution was analyzed by HPLC with UV detection. Conditions of the HPLC system were; wavelength o f 220nm, sensitivity of 0.04Aufs, flow rate of 1.5 mL /min; mobile phase of 80%methanol and 20%water and C 18 column All the standards and the samples were added to HPLC vials in methanol to make up 1 mL of at least 70% methanol. Samples were injected thri ce in the HPLC system The run time was 8 minutes and retention time was 6 minutes. Concentrations that were below detection limit after dilution of samples in HPLC vials were spiked with a known concentration of d ieldrin in pure methanol. The adsorbed con centration (S e ) was calculated using Eq. 3 13 and was plotted against the solution concentration (C e ). The slope of the line is equal to the sorption coefficient (K M ) based on Eq.12. Equations 3 1, 3 9, and 3 10 were used to calculate properties of Dieldrin (cosolvency

PAGE 40

4 0 c ), sorption coefficient in water (K W ), and HSA). The values of K W were normalized with soil organic carbon content to calculate K OC for each soil.

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41 Table 3 1: Characteristics of the s oils used Soil series name Location Classificat ion Chekika Miami Dade County, Florida Loamy skeletal, carbonatic, hyperthermic Lithic Udorthents. Krome Miami Dade County, Florida Loamy skeletal, carbonatic,hyperthermic Lithic Udorthents Perrine, marl Miami Dade County, Florida Coarse silty,carbonati c,hyperthermic Typic Fluvaquents Lauderhill Miami Dade County Euic hyperthermic Lithic Haplosaprists Monteocha Alachua County Florida Sandy, siliceous hyperthermic Ultic Alaquods Monteocha Table 3 2 Some p roperties of the s olvents (at 25 o C) u se d Solvent Boiling Point ( o C ) Viscosity ( cP ) Surface Tension ( dyn e /cm ) Density ( g/ mL 3 ) Rohrschneider Polarity index Dipole Moment ( D ) Dielectric constant Water 100 0.89 73 1.0 9.0 1.84 80.0 Methanol 65 0.54 22 0.77 6.6 1.66 32.7 Source : Snyder et al. (1978) Table 3 3 Summary of initial and equilibrium concentrations used for sorption isotherms Chemical Type f c range for isotherm C o (ug/ mL ) C e range (ug/ mL ) Sorbent (s) endosulfan 12 C 0.1 1 11 5 9 HPLCV + TLCT Dieldrin 12 C 0.25 0.4 2.5 5 1 2.5 HPLCV Dieldrin 12 C 0.1 0. 6 2 3 1 2.5 TLCT Dieldrin 12 C 0.3 0.6 4 8 1.3 2.6 Soils Anthracene 12 C and 14 C 0.01 0. 6 0.1 0.05 0.09 TLCT Anthracene 12 C and 14 C 0.5 0.7 0.1 0.01 0.06 Soils DDT 12 C and 14 C 0.05 0. 5 0.01 0.02 0.009 0.02 TLCT DDT 12 C and 14 C 0.5 0.6 0.02 0.04 0.009 0.02 Soils

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42 Figure 3 1. Sorption of a chemical up to HPLC analysis Figure 3 2. Sorption of a chemical up to LSC analysis Centrifuge tube Pipette tip Vial with a cocktail Stock Solution To LSC Analysis Centrifuge tube Pipette tip Vial HPLC Column Detector Loop Tube (metal) Tube (Plastic) Needle Stock Solution Waste

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43 Figure 3 3. Calculation of the area of HPLC vials covered by solution Area: 4.76cm 2 Volume = 1mL Radius = 0.5cm Height = 1.25cm

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44 Figure 3 4. Calculation of the area of Teflon Lined Ce ntrifuge Tubes covered by solution 5mL = 22.26cm 2 10mL=38.53 cm 2

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45 CHAPTER 4 RESULTS AND DISCUSSI ON In this study, initially, sorption of e ndosulfan d ieldrin, a nthracene, and DDT, on container walls (Teflon lined centrifuge tubes and HPLC vials) in methanol water systems with me thanol ranging from (f c = 0.01 to 1) were determined. Then the range of fraction of methanol (f c ) where there was no sorption on container walls w as identified A bove th at range of methanol f c sorption coefficients (K M ) of a nthracene DDT and d ieldrin, w ere determined in five soils (Perrine, Krome, Chekika, Lauderhill and Monteocha). The aqueous (f c = 0) sorption coefficient (K W ) of each chemical was calculated using the S olvophobic model. The K W values were normalized with soil organic carbon content to obtain K OC values for each chemical in all soils. The parameters that were used to calculate HSA, K OC and K M of each chemical are listed in Table 4 1. Sorption on Container Walls Sorption of 12 C endosulfan on Teflon Lined Centrifuge Tubes (TLCT) and HP LC Vials (HPLCV) Data in Fig s. 4 1 and 4 2 show Endosulfan adsorbed on the container walls (TLCT and HPLCV) up to 0.5 f c with little sorption at f c = 0.7 Data in Figs. 4 1 and 4 2 also reveal that the S olvophobic model describe the data reasonably well. The percent recovery in water (f c = 0) was calculated as 30 % The s orption coefficient endosulfan in an aqueous system (K W ) from Figure 4 1 was 0.60 2 Although sorption on container walls is not needed, sorption on container walls was use d to calculate HSA for endosulfan of 176 2 using Eq. 3 9 and parameters listed in Table 4 1. No data are available in the literature for endosulfan HSA or TSA. Nkedi Kizza et al., (1985) pointed out that the value of the slope of the line in Fig. 4 1 depends on the properties of methanol, water, and endosulfan and therefore the HSA calculated should not be affect ed by the nature of the sorbent. However, the magnitude of K W

PAGE 46

46 calculated depends on the properties of the sorbing materials, in this case T LCT and HPLC vials. In many studies of organic chemicals, TLCT and HPLCV are assumed not to adsorb chemicals such as endosulfan The data presented show that the concentration of endosulfan if measured in aqueous system with HPLC UV would be reduced by 70%. Sorption of 12 C Dieldrin on C ontainer W alls Sorption on HPLC v ials (HPLCV) and T eflon lined centrifuge t ubes (TLCT) The dependence of K M on f c for d ieldrin sorption by two container walls (TLTC and HPLCV) is shown in Fig 4 3. As predicted by the S olvophobic theory (Eq. 3 1) a log linear relationship describes the data over the range of 0.1 c 0.5. The slopes of the lines in Fig. 4 3 c (Table 4 1) is independent of the sorbent as predicted by Eq. 3 1. Similar trend in data was reported for a nthracene sorption on 4 soils in methanol w ater systems (Nkedi Kizza, et al., 1985). The calculated aqueous sorption coefficient values ( K W ) for Dieldrin were 0.57 and 3.24 2 on TLCT and HPLV container walls, respectively. Data in Figs. 4 4 and 4 5 further emphasize that HPLCV sorb more d i eldrin than TLCT. The percent recovery in aqueous systems was estimated as 6 and 32% for HPLCV and TLCT, respectively. Another observation is that d ieldrin is not adsorbed on HPLCV at f c 0.70 compared to TLCT in which there is no sorption of d ieldrin at f c e that sorption experiments o f d ieldrin should be determined in methanol at f c However, for the analysis of d ieldrin with HPLC UV, the analyte in HPLC glass vials should be in methanol at f c data in Figs. 4 4 and 4 5 describe the percent recovery well as predicted by the theory (Eq. 3 6). In Fig. 4 6, the plot of the relative sorption coefficient [ln (K M /K W )] VS f c is shown for Dieldrin sorption on HPLCV and TLCT container wa lls. The sorption data from TLCT and HPLC vials are described by one line as expected from Eq. 3 c value calculated from the

PAGE 47

47 slope of the line in Fig. 4 c c value of 10.67 and 10.75 for HPLCV and TLC c values were used to calculate HSA of d ieldrin using Eq. 3 9 and appropriate values of ( c k and T) listed in Table 4 1. The HSA for d ieldrin was 221 2 (Table 4 2) Sorption of 14 C Anthracene on Teflon Lined Centrifuge Tubes (TL CT) The dependence of K M on f c for anthracene sorption by container walls of TL CT is shown in Fig 4 7. As predicted by the S olvophobic theory (Eq. 3 1) a log linear relationship describes c 0.25. The line was extende d to f c = 0 to estimate K W The calculated aqueous sorption coefficient ( K W ) value for a nthracene on TLCT container walls was 2 The percent recovery (in aqueous systems) for sorption of a nthracene on TLCT container walls was estimated to be 52% (Fig. 4 8). Anthracene is not adsorbed on TLCT at f c 0.45. This implies that sorption experiments on a nthracene should be determined in methanol water mixtures at f c c value calculated from the slope of th e line in Fig. 4 c = 0.83) was 9.83. c values were used to calculate HSA of a nthracene using Eq. 3 9 and appropriate values of ( c k and T) listed in Table 4 1. The HSA for a nthracene was 203 2 very close to the literature value o f 202 2 (Nkedi Kizza et al., 1985) Since a nthracene has no functional groups, its TSA is equal to HSA. This gives credibility to the use of the S olvophobic model in this study. Sorption of 14 C DDT on Teflon Lined Centrifuge Tubes (TLCT) The dependence of K M o n f c for DDT sorption by container walls of TL CT is shown in Fig 4 9. As predicted by the S olvophobic theory (Eq. 3 1) a log linear relationship describes the data over the range of 0.05 c 0.30. The line was extended to f c = 0 to estimate K W The calculated aqueous sorption coefficient (K W ) value for DDT on TLCT container walls was 0.67 2 The percent recovery (in aqueous systems) for sorption of DDT on TLCT container

PAGE 48

48 walls wa s estimated to be 29% (Fig. 4 10). DDT is not adsorbed on TLCT at f c implies that sorption experiments on DDT can be determined in methanol water mixtures at f c 0.45 to eliminate sorption on TLCT. c value calculated from the slope of the line in Fig. 4 c = 0.83) was 12.94. c values were used to calculate HSA of DDT using Eq. 3 9 and appropriate values of ( c k and T) listed in Table 4 1. The HSA for DDT was 322 2 No data in the literature are available for compar ison. Conclusions Sorption of four strongly hydrophobic chemicals on container walls of T eflon lined centrifuge tubes and HPLC vials has been demonstrated. Using d ieldrin sorption data on HPLC v ials and Te flon l ined c entrifuge t ubes; HPLC v ials sorb more d ieldrin than T eflon l ined c entrifuge t ubes in aqueous systems. This was confirmed by low recovery of endosulfan that was sorbed on both TLCT and HPLCV. In aqueous systems, the sorption on TLCT container walls was predicted to be in the order DDT > Dieldrin > Anthracene (Table 4 2) For all three SHOCs there was negligible sorption on TLCT at f c However, it is clear that glass HPLC vials sorb these chemicals at f c < 0.7. To eliminate sorption on T eflon l ined c entrifuge t ubes and to determine soil sorption coefficients of d ieldrin, DDT, and a nthracene in these tubes, experiments should be conducte d in methanol water mixtures at f c If HPLC UV is the method of detection of SHOCs in solution, the analyte should be prepared i n Literature data that support findings in this study have reported that 40 80% of the poly chlorinated b iphenyls (PCBs) in a sample may be adsorbed on to the poly tetrafluoroethylene (PTFE) surfac e ( Baltussen et al., 1999, Lung et al., 2000 )

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49 It was interesting to find that the h ydrocarbonaceous s urface a endosulfan, d ieldrin, DDT, and a nthracene c ould be calculated from sorption data on container walls. The HSA values are summarized in Table 4 2. It appears that the S olvophobic model was appropriate for this study. Sorption Isotherm Ex periments Sorption isotherm experiments for sorption of chemical s by soils were carried out to determine sorption coefficients in mixed solvents (K M ) and there after extrapolate to aqueous systems using the S olvophobic model to obtain sorption coefficients (K W ). Then soil sorption ceoefficient values (Koc) were calcula ted by d i viding K W with organic carbon fractions (OC) of soils. Sorption data on soils were also used to calculate h ydrocarbonaceous s urface a reas (HSA) of the chemicals. Sorption of Dieldrin on Soils The exponential decrease in sorption coefficients (K M ) of d ieldrin in mixed solvents with increasing methanol fractions ( f c ) is shown in Fig. 4 11, for 5 soils. The slopes of these lines are c ) is independent of the sorbents (soils) used. Plots of relative sorption coefficients (K M /K W ) for all soils were therefore described as a single line (Fig 4 1 2 ) from which effective HSA was calcula ted. The soil sorption coefficients in aqueous systems (K W ) were calculated from the intercepts of the plots (Fig. 4 11). Similar trend in data were reported fo r sorption of diuron and a trazine in soils (Nkedi Kizza et al., 1985). c ) values from so rption of d ieldrin by Chekika, Krome, Perrine, Lauderhill, and Monteocha, were used to calculate H SA values. The HSA values were very close to the effective 2 The data are summarized in Table 4 3. The H SA values are a lso close to those determined for d ieldrin sorption on container walls (Table 4 2).

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50 From literature, sorption is directly proportional to organic carbon content of the soil. The trend of sorption coefficients in aqueous systems (K W ) as shown in Table 4 3 i s proved to be true for all soils. When s orption coefficients in aqueous systems (K W ) were normalized with organic carbon content of the soils to obtain soil Koc values, all soils except Krome gave values close to each other (Figure 4 13). However, d ieldri n sorption coefficient value in Krome is within a factor of two (Karickhoff, 1981). The low organic carbon content (Karickhoff, 1984) of Krome can explain the deviation of d ieldrin Koc value from other soils. Data in Fig.4 14 show an average Koc of 4803 fo r all soils. The Koc values obtained in this st udy are much less than what is reported in the literature (Table 2 2) which implies that sorption on container walls is a factor for the variation of Koc values of strongly hydrophobic organic chemicals. Sorpt ion of Anthracene on Soils Sorption of a nthracene on soils was done to show the validity of S olvophobic model. Anthracene served as an ideal sorbate for evaluating the So lvophobic theory because its sorption is characterized by solvophobic interactions sin ce the h ydrocarbonaceous s urface a rea H SA is equal to t otal surface a rea TSA The exponential decrease in sorption coefficients (K M ) in mixed solvents with increasing methanol fractions (f c ) is shown in Fig. 4 15 for Krome soil. The K M data in Fig. 4 15 were obtained at 0.45 c re t here is negligible sorption of a nthracene on TLCT container walls. These data were used in the model. The K M values for anthracene sorption a t f c = 0.1, 0.2 and 0.3 were directly measured by combusting 14 C Anthracene to determine the amount adsorbed on the soil. The K M values at f c = 0.1, 0.2, and 0.3 are also described by the theory (Eq. 3 1). This emphasizes that K M data collected at f c >> 0 can be used to estimate K W at f c = 0. However, if sorption on container wal ls is ignored, the K M values measured at f c = 0.1, 0.2, and 0.3 will give a very high K W (1012 mL/g)) resulting in a nthracene K OC of 101, 200. This K OC value is about 5 times larger than the K OC of 18752 that was obtained

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51 for a nthracene sorption by Krome that when there was no sorption on container walls on container walls (Table 4 4). The dependence of K M values on f c for Anthracene sorption by four soils from methanol water mixtures at which there no sorption on TLCT walls is shown in Fig. 4 16. As pre dicted by the S olvophobic theory (Eq. 3 1), a log linear relationship describes the data for all soils. The slopes of the lines are essentially the same because the co c ) is independent of the sorbents (soils). Plots of relative sorption coefficients (K M /K W ) for all soils were therefore described as a single line (Figure 4 17) from which effective HSA was estimated as 203 2 The HSA values from sorption of a nthracene on Krome, Chekika, Perrine, Monteocha, and Lauderhill (Table 4 4) were very close to the value of 202 2 that is reported in the literature (Yalkowsky et al., 1979). The H SA values are also close to the values obtained for the sorption of An thracene on TLCT container walls (Table 4 2). As was observed for d ieldrin sorption in soils, sorption is proportional to organic carbon content of the soil. The trend of sorption coefficients in aqueous systems (K W ) can be seen (Table 4 4). Since soil org anic carbon increases in the order Lauderhill> Perrine> Chekika > Krome, the K M values also increase in the same order. When Sorption coefficients in aqueous systems (K W ) were normalized with organic carbon content of the soils to obtain Koc values, the va lues did not give constant figures across all the soils. Although most of the values are with in the acceptable factor of two, some go beyond that factor. The low organic carbon content (Karickhoff, 1984) of the carbonatic soil Krome might have caused the difference in K OC values as was also observed for d ieldrin sorption in Krome. As was observed for d ieldrin sorption, Perrine soil has the lowest K OC value for Anthracene. The average a nthracene Koc value for all

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52 the soils of 8886 was obtained from the slop e of the plot of sorption coefficients in aqueous systems (K W ) against the organic carbon content as shown in Figure 4 19. Sorption of DDT on Soils The exponential decrease in sorption coefficients (K M ) in mixed solvents with increasing methanol fractions (f c ) is shown in Fig. 4 20 for Krome soil. The K M data in Fig. 4 19 were obtained at 0.50 c These data were used in the model. The K M values for DDT sorption at f c = 0.3, and 0.4 w ere directly measured by combusting 14 C DDT to determine the amount adsorbed on the soil. The K M values at f c = 0.3 and 0.4 are also described by the theory (Eq. 3 1). This implies that K M data collected at fc >> 0 can be used to estimate K W at f c = 0. A si milar trend in data was observed for a nthracene sorption in Krome soils. The exponential decrease in sorption coefficients (K M ) in mixed solvents with increasing methanol fractions (f c ) is shown in Figures 4 21 with slopes of the lines essentially the same c ) is independent of soils. Plots of relative sorption coefficients (K M /K W ) for all soils were therefore described as a single line (Figure 4 22) c from Fig. 4 22 was used to calculate th e HSA of DDT which was 322 2 The HSA values from sorption of DDT by Chekika Krome, Perrine, Lauderhill, and Monteocha soils were 323, 326, 319, 2 respectively, as shown in Table 4 5. Note that a similar HSA value of 322 2 was obtain ed from DDT sorption on TLCT container walls. From literature data, sorption is proportional to organic carbon content of the soil (Table 4 1). The trend of sorption coefficients in aqueous systems (K W ) as shown in Table 4 2 is generally proved to be tru e for all soils. When Sorption coefficients in aqueous systems (K W ) were normalized with organic carbon content of the soils to obtain Koc values, the data were within a

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53 factor of two for three soils (Krome, Monteocha, and Lauderhill). The two other carbo natic soils had K OC values lower than a factor of three. Such low K OC values for Perrine and Chekika have been reported for d iuron and a trazine (Nkedi Kizza et al., 2006). The average Koc from all soils was calculated to be 195 665. The K OC values obtained from this study for DDT are much lower than those reported in the literature (Table 2 1). The K OC values from this study varied within a factor of 4 compared to a factor of 13 reported in the literature (Table 2 1). This implies that sorption on containe r walls might be a serious c ause of variability in literature K OC values for DDT. Conclusions DDT sorbed most on the soils followed by Anthracene and the least sorption was observed for d ieldrin, which is a reflection of aqueous solubility of these chemica ls. The three chemicals have very low aqueous solubility which makes it difficult to measure sorption in water. All three chemicals would strongly sor b on T eflon lined centrifuge tubes and HPLC vials in aqueous systems. Consistent sorption data in soils fo r SHOCs can be obtained while measuring sorption in mixed solvents that will eliminate sorption on container walls and vessels.

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54 Table 4 1. Parameters used to calculate chemical properties (HSA, K OC and K M ) Parameter/Soil Value Source 2) 1.99 *10 15 Nkedi Kizza et al. (1985) k (ergs/K) 1.38*10 16 T 298 (K) Room temperature c 0.83 Karickhoff, (1981) Chekika OC (g/g) 0.02 This study Krome OC (g/g) 0.01 This study Perrine OC (g/g) 0.03 This study Monteocha OC (g/g) 0.07 This study Lauder hill OC (g/g) 0.31 This study TLCT surface area for 10 mL (A, cm 2 ) 38.53 This study HPLCV surface area for 1 mL (A, cm 2 ) 4.76 This study Table 4 endosulfan, Anthracene and Dieldrin on c ontainers. Chemical (Sorbent) K W 2 ) % R ecovery at f c = 0 100 % recovery f c c HAS ( 2 ) Endosulfan(HPLC V +TLCT) 0 .6 0 30 7 0 8.65 17 6 Dieldrin(HPLCV) 3.2 4 6 70 10.67 22 1 Dieldrin(TLCT) 0.57 3 2 4 5 10.75 22 1 Dieldrin (TLCT and HPLCV) NA NA NA 10.69 221 DDT(TLCT) 0.67 2 9 4 5 15.59 322 Anthra cene (TLCT) 0.2 4 5 2 45 9.81 20 3 NA = Not applicable

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55 T able 4 3. Sorption c oefficients ( K W and Koc), c c ) and h ydrocarbonaceous surface area (HSA) for Dieldrin Parameter Perrine Chekika Krome Monteocha Lauderhill All soils K W (L/kg) 119 99 86 314 1495 c 10.72 10.71 10.67 10.98 10.51 10.72 HSA ( 2 ) 222 221 221 227 217 222 K OC (L/kg) 3961 4 945 8 566 4 478 4 823 4 803 Table 4 4. Sorption c oefficients ( K W and Koc), c c ) and h ydrocarbonaceous surface areas (HSA) for Anthracene Parameter Perrine Chekika Krome Lauderhill All soils K W (L/kg) for f c = 0.5, 0.6, 0.7 110 128 188 2770 K OC (L/kg) for f c = 0.5, 0.6, 0.7 3,669 6,418 18,752 8,935 K W (L/kg) for f c = 0.1, 0.2, 0.3 NA NA 1012 NA K OC (L/kg) for f c = 0.1, 0.2, 0.3 NA NA 101200 NA c 9.83 9.78 9.86 9.78 9.81 HSA( 2 ) 203 202 203 202 203 K OC (L/kg) for f c = 0.5, 0.6, 0.7 8,886 NA = Not applicable Table 4 5. Sorption c oefficients (Koc), c c ) and h ydrocarbonaceous surface areas (HSA) for DD T Parameter Perrine Chekika Krome Monteocha Lauderhill All soils K W (L/kg) 1,703 1,236 2,101 11,614 61,698 NA K OC (L/kg) 56,758 61,823 210,065 165,920 196,489 195 665 ( c ) 15.43 15.58 15.76 15.43 15.67 15.59 HAS ( 2 ) 319 323 326 319 324 322 NA = Not a pplicable

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56 Figure 4 1. Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c Endosulfan by Teflon Lined Centrifuge Tubes and HPLC Vials Figure 4 Endosulfan sorption on Teflon Lined Centrifuge Tubes and HPLC Vials

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57 Figure 4 3 Log linear relationship between s orption coefficient (K M ) and fraction of methanol (f c ) for sorption of Dieldrin by Teflon Lined Centrifuge Tubes and HPLC Vials Figure 4 4. Percent recovery of Dieldri n sorption on HPLC Vials

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58 Figure 4 5 Percent r ecov ery of Dieldrin sorption on Teflon Lined centrifuge Tubes (TLCT) Figure 4 6. Relative sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for Dieldrin sorption by Teflon Lined Centr ifuge Tubes and HPLC Vials.

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59 Figure 4 7 Log linear relationship between s orption coefficient (K M ) and fraction of methanol (f c ) for sorption of Anthracene by Teflon Lined Centrifuge Tubes Figure 4 8 Percent r ecov ery of Anthracene sorption on Teflon Lined centrifuge Tubes

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60 Figure 4 9 Log linear relationship between s orption coefficient (K M ) and fraction of methanol (f c ) for sorption of DDT by Teflon Lined Centrifuge Tubes Figure 4 10. Percent Recoveries of Dieldrin sorption on Teflon Lined Centr ifuge Tubes

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61 Figure 4 11. Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of Dieldrin by soils Figure 4 12. Relative sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for Dield rin sorption by soils.

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62 Figure 4 13. Dieldrin KOC from different soils Figure 4 14. Relationship between the sorption coefficient (K W ) and soil organic carbon content (OC) for sorption of Dieldrin by soils

PAGE 63

63 Figure 4 15. Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of Anthracene by Krome soil.

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64 Figure 4 16. Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of Anthracene by soils

PAGE 65

65 Figure 4 17. Relative sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for Anthracene sorption by soils.

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66 Figure 4 18. Anthracene K OC values from different soils Figure 4 19. Relationship between the sorption coefficient (K W ) a nd soil organic carbon content (OC) for sorption of Anthracene by soils

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67 Figure 4 20. Log linear relationship between sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of DDT by Krome soil. Figure 4 21. Log linear relationship betwee n sorption coefficient (K M ) and fraction of methanol (f c ) for sorption of DDT by soils.

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68 Figure 4 22. Relative sorption coefficient (K M /K W ) as a function of fraction of methanol (f c ) for DDT sorption by soils. Figure 4 23. DD T K OC values from different soils DDT Soil K OC 0 50000 100000 150000 200000 250000 Perrine Chekika Kr ome Monteocha Lauderhill SOIL K OC

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69 Figure 4 24. Relationship between the sorption coefficient (K W ) and soil organic carbon content (OC) for sorption of DDT by soils.

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70 CHAPTER 5 CONCLUSIONS Sorption on container walls (Teflon, glass, and polycarbonate) by strongly hydrophobic organic chemicals (SHOCs) was observed in this study. This experimental error plays a significant role in reducing analyte integrity before the actual sample concentration is measured by HPLC or TLC in aqueous systems. This is mainly due to the very low aqueous solubility of these chemicals This research also alerts manufacturers of containers that all containers tested adsorb SHOCs during storage and multi step analysis in aqueous systems. Based on this research storing Dieldrin an d DDT dissolved i n water for 24 hours in Teflon lined centrifuge t ubes gives less than 40% recovery of original concentrations of dieldrin and DDT. Soil sorption isotherms therefore should be done in mixed solvents for example methanol and water that elimi nate sorption on containers. DDT sorbs more than dieldrin on T eflon lined centrifuge t ubes in aqueous systems. Samples of SHOCs when put in HPLC glass vials before HPLC analysis are subject to ad sor ption on glass walls. This phenomenon was clearly demonst rated by sorption of d ieldrin on HPLC vials. HPLC vials sorb more d ieldrin tha n T eflon lined centrifuge t ubes Reasonable values of cosolvency powers and h ydrocarbonaceous surface areas of strongly hydrophobic organic chemicals can be calculated by fitti ng data for sorption on container walls and by soils using the S olvophobic model since cosolvency powers of these chemicals are independent of the sorbents The Koc values obtained in this study using mixed solvent system and thus eliminating sorption on container walls varied much less than those reported in the literature for dieldrin and DDT. This implies that sorption on container walls plays a significant role in the varia bility of the literature Koc values. It also shows that the S olvophobic model ca n be used to calculate the

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71 aqueous sorption coefficient by extrapolating to zero fraction of cosolvent ( methanol ) However, K OC values of carbonatic soils seem to be lower than values from non carbonatic soil. This was attributed to the source and nature o f organic matter in carbonatic soils that might be different from that of non carbonatic soils. Generally sorption of DDT, anthracene, and d ieldrin was directly proportional to soil organic carbon content. The trend of sorption of the chemicals on the soil s was in the same order as their aqueous solubilit ies (DDT > Anthracene > Dieldrin). The trend agrees with the literature data. Although sorption of the chamicals on organic carbon is only examined, sorption on other soil components like clays and carbon ates should be investigated in future research. This study has shown high K OC values for Krome (OC = 1%) compared to organic soil, Lauderhill (OC = 31%) which emphasizes the argument that there could be other soil components sorbing SHOCs Further examinat ion of the hydrophobicity of the organic carbon of the carbonatic soils is needed. For example this study has consitently shown that sorption coefficients values (K OC ) of Krome ( OC = 1%) are higher than those of Perrine ( OC = 3%) yet this would be the oppo si te according to literature data.

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72 LIST OF REFERENCES Abraham.M.A., Kamlet.M.J., Doherty.R.M., Carr.P.W., Doherty.R.F., and Taft.R.W., 1987. Linear solvation energy relationships: Important differences between aqueous solubilty relationships for ali phatic and aromatic solutes. J. Phys. Chem. 91: 1996 2004. Aleksandar Sabljic 1984. Predictions of the Nature and s trength of s oil s orption of o rganic p ollutants by m olecular t opology. J. Agric. Food Chem. 32: 243 246 Baltussen, E., David, F., Sandra P ., Jansen, H G and Cramers,C. 1998. Retention model for sorptive extraction thermal desorption of aqueous samples: Application to the automated analysis of pesticides and poly aromatic hydrocarbons in water samples. J Chromatogr A. 805:237 247 Baltus sen,E., Sandra, P., David, F., Jassen, H G., and Cramers, C.1999. Study in to equilibrium mechanism between water and poly (dimethyl siloxane) for very apolar solutes: Adsorption or sorption? Anal Chem. 71: 5213 5216 Beland,P., De Guise,S., Girard,C., La gace,A., Martineau,D., Michaud,R., Muir,D.C.G., Norstrom,R.J., Pelletier,E., Ray,S and Shurgart,L.R. 1993. Toxic compounds and health and reproductive effects in St. Lawrence beluga whales. J.Great Lakes Res. 19:766 775 Bergman,A., and M. Olsson. 1985. Pathology of Baltic grey seal and ringed seal females with special reference to adrenocortical hyperplasia: is environmental pollution the cause of a widely distributed disease syndrome? Finish Game Research. 44: 47 62 Bosveld, A.T.C., and Van den Berg.M. 1994. Effects of PCBs, PCDDs and PCDFs on fish eating birds. Environ. Rev. 2:147 166 Brusseau M.L., Jessup, R.E.and Rao P. S.C. 1991. Nonequilibrium s orption of o rganic c hemicals: Elucidation of r ate l imiting p rocesses. Environ. Sci. Technol 25 1991. Ch iou, C. T., Schmedding, D. W. and Manes M.2005. Improved p rediction of o ctanol w ater p artition c oefficients from l iquid s olute w ater s olubilities and m olar v olumes. Enviro n Sci. Technol. 39: 8840 8846 Chiou, C.T., 1990. Roles of organic matter, mineral s, and moisture in sorption of nonionic compounds and pesticides by soil. ASA SSSA, Madison, pp.111 160. Edwards, C .A. 1987. The environmental impact of pesticides. Parasitis 86:309 329 Giesy, J.P., Ludwig, J.P and Tillitt, D.E. 1994. Embryolethalit y and deformities in colonial, fish eating, water birds of the great lakes region: Assessing casuality. Environ.Sci.Technol. 28:128A 135A. Guillete, L.J. 2000. Organochlorine pesticides as endocrine disruptors in wild l ife. Central European Journal of Pu blic H ealth 8(suppl.): 34 35.

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73 Hillel, D., 1982. Introduction to soil physics. Academic Press, London. Jones K.C and de Voogt, P. 1999. Persistent Organic Pollutants (POPs): State of the science. Environ.Pollut.100:209 221. Karichkoff, S. W. 1981. Semi emperical estimation of sorption of hydrophobic pollutants on natural sediments and soils. Chemosphere, 10:833 846 Karickhoff, S.W.1984. Organic pollutant sorption in aquatic systems. Journal of Hydraulic Engineering. 110: 707 735. Karick hoff, S.W., 1985. Pollutant sorption in environmental systems. Environment al Exposure from Chemicals. 1 ; 49 64 Kavlock, R.J. 1996. Research needs for the risk assessment of health and environmental effects of endocrine disruptors. Environ. Health Perspec. 104:715 740 Kidd, H ., and James, D.R 1991 The a grocemicals h and book, Third edition. Royal Society of Chemistry Information Services, Cambridge UK 6 10 Lee L.S. and Rao, P.S.C Impact of several water miscible organic solvents on sorption of benzoi c acid by soil. Environ. Sci. Technol. 30:1533 1539. Lidia, W., Magdalena, R.A., and Jacek N 2005. Determining PAHs and PCBs in aqueous samples: finding and evaluating sources of error. Anal Bioanal Chem, 382: 1389 1397. Linkov, I., Ames, M. R. Crouc h, E. A. C. and Satterstrom, F K. 2005. Uncertainity in octanol water partition coefficient: Implications for risk assessment and remedial c osts. Environ. Sci. Technol.39:6917 6922 Manoli,E., and Samara,C., 1999. Polycyclic aromatic hydrocarbons in wat ers: Sources, occurrence, and analysis. Trends Anal. Chem.18:417 428. Munro, I.C., Doull, M.D., Giesy, J.P., Mackay, D, and Williams. G. 1994. Interpretive review of the potential adverse effects of chlorinated organic chemicals on human health and env ironment. Regulatory Toxicology and Pharmacology. 20:1 1056 Namiesnik, J. 2000. Trends in environmental analytics and monitoring. Crit Rev Anal Chem 30: 221 241 Namiesnik, J. 2002. Trace analysis challenges and problems. Crit Rev Anal Chem 32: 271 300. Nkedi Kizza, P., Rao, P.S.C. and Johnson, J.W. 1983. Adsorption of diuron and 2, 4, 5 T on soil particle size separates. J.Environ. Qual. 12:195 197.

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74 Nkedi Kizza, P., Rao, P. S. C. and Hornsby A G. 1985. Influence of organic cosolvent on sorption of tox ic organic substances (TOS) in soils. Environ. Sci. Technol. 19:975 979. Pearce,P.A., Peakall, D.B. and Raynolds, L.M. 1979. Shell thin n ing and residues of organo chlorines and mercury in sea bird eggs. Pestic. Monit. J. 13:61 68. Pontolillo, J., and Egan house R. 2001. The search for reliable a queous s olubility (S W ) and o ctanol w ater partition c oefficient (K OW ) d ata for h ydrophobic o rganic c ompounds: DDT and DDE as a c ase study. U.S. Geological S urvey, water resources i nvestigation report 01 4201. Reston, Virginia. Ratcliffe,D.A. 1967. Decrease in eggshell weight in certain birds of prey. Nature 215(5097): 208 210 Rao P.S.C., and Davidson, J.M 1980. Estimation of pesticide retention and transformation parameters required in nonpoint source pollution mod els. Environ. Impact Nonpoint Source Pollut. pp 23 67. Rao, P. S. C., Hornsby, A G. Kilcrease D. P., and Nkedi Kizza P 1985. Sorption and transformation of h ydrophobic o rganic c hemicals in a queous and m ixed s olvent s ystems: Model d evelopment and p reli minary e valuation. J. Environ. Qual. 14:376 382 Rao, P.S.C., L.S. Lee, and R. Pinal.1989 Cosolvency and sorption of hydrophobic organic chemicals. Environ. Sci. Technol.24, 647 654. Reijnders, P.J.H. 1986. Reproductive failure in common seals feeding on fish from polluted coastal waters. Nature. 324:456 457 Renner, R. 2002. The K OW controversy. Environ. Sci. Technol. 441A 413A. Ritter, L., Solomon, K. R. Forget, J. Stemeroff, M. and C. 1995. An assessment report on: DDT Aldrin Dieldrin Endrin Chlordane Heptachlor Hexachlorbenzene Mirex Toxaphene, Polychlorinated Biphenyls, Dioxin and Furans. IPCS and IOMC. Sangster, J 1997. Octanol water partition coefficients F undamentals and physical chemistry. New York, Marcel Dekker. Schwarzenbach R.P ., Schellengerg K and Leuenberger, C.1984 Sorption of c hlorinated p henols by n atural s ediments and a quifer m aterials. Environ. Sci. Technol. 18: 652 657 Smith, A.G. 1991. Chlorinated hydrocarbon insecticides in hand book of pesticide toxicology. San Di ego,California.

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75 Stockholm C onvention. 2001. Conference of p lenipotentiaries on the a doption and s igning of the Stockholm Convention on Persistent Organic Pollutants Stockholm, Sweden, 21 23 May. Torrence,C., and Webster, P.J. 1998. The annual cycle of persistence in the ElNino southern oscillation. Q.J. Roy. Met. Soc. 124:1985 2004 Nzengung, V.A., Nkedi Kizza, P., Ron, E. J., and Evangelos, A. V. 1997. Organic cosolvent effects on sorption kinetics of hydrophobic organic chemicals by organoclays. Envi ron. Sci. Technol. 31: 1470 1475. Vowles, P.D., and Montoura, R.F.C., 1987. Sediment water partition coefficients and HPLC retention factors of aromatic hydrocarbons.Chemosphere, 16:109 116. Walkey A. and Black I. A. 1934. An examination of Degtjaref f method for determining soil organic matter and a proposed modification of the chromic acid titration method. Soil Sci. 37: 29 38. Weber, W J Paul Jr., McGInIey, M and Katz, L E. 1992. A d istributed r eactivity m odel for s orption by s oils and s edimen ts. Conceptual b asis and e quilibrium a ssessments. Environ. Sci. Technol. 26: 1955 1962 Wolska, L., Rawa Akkonia, M. and Namiesnik, J 2005. Determining PAHs and PCBs in aqueous samples: finding and evaluating sources of error. Anal.Bioanal. Chemm.382:1389 1397 Worthing C.R., and Walker, S.B.1983. The pesticide manual. 7 th ed. Lavenham P ress L imited, British C rop P rotection C ouncil, London. WWF .1998, Resolving the DDT dilemma: Protecting the b iodiversity and h uman h ealth, WWF Canada and WWF USA Washin gton D.C. pp 1 52. WWF (and refs therein).1999 Hazards and e xposures a ssociated with DDT and s ynthetic p yrethroids u sed for v ector c ontrol, Washington D.C. pp 1 46. Yalkowsky, S.H., and S.C. Valvani. 1979. Solubilities and partitioning: Relationship be tween aqueous solubilities, partition coefficients, and molecular surface areas of rigid aromatic hydrocarbons. Chem. Eng. Data 24: 127 129. Zhough, M.., Li, Y. C. Nkedi Kizza, P. and K. 2003. Endosulfan losses through runoff and leaching fro m calcareous gravelly marl soils. Vadose Zone 2:231 238

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76 BIOGRAPHICAL SKETCH Augustine Muwamba is a Ugandan by nationality who was born on July 10, 1980. He got his undergraduate degree (B.S. in Agriculture) in 2005 from Makerere University, Kampala, Ugand a. He immediately started his MS in fall 2005 at University of Florida and got his MS degree in S oil and W ater S cience in f all 2007. He will start his Ph D program in spring 200 8 in the S oil and W ater S cience D epartment at the University of Florida.