sorption and transport of veterinary antibiotics in agroforestry buffer, grass buffer and cropland soils

174 Pages·2011·2.14 MB·English

by  Gerald L Mitchell

SORPTION AND TRANSPORT OF VETERINARY ANTIBIOTICS IN
AGROFORESTRY BUFFER, GRASS BUFFER AND CROPLAND SOILS
_______________________________________
A Dissertation
Presented to
The Faculty of the Graduate School
University of Missouri-Columbia
_______________________________________________________
In Partial Fulfillment
Of the Requirements for the Degree
Doctor of Philosophy
_____________________________________________________
by
BEI CHU
Drs. Keith W. Goyne and Stephen H. Anderson, Dissertation Supervisors
December 2011
The undersigned, appointed by the dean of the Graduate School, have examined the
dissertation entitled

SORPTION AND TRANSPORT OF VETERINARY ANTIBIOTICS IN
AGROFORESTRY BUFFER, GRASS BUFFER AND CROPLAND SOILS

Presented by
Bei Chu
A candidate for the degree of
Doctor of Philosophy
and hereby certify that, in their opinion, it is worthy of acceptance.
Dr. Keith W. Goyne (Chair)
Dr. Stephen H. Anderson (Co-Chair)
Dr. Chung-Ho Lin
Dr. Robert N. Lerch
ACKNOWLEDGEMENTS

Finishing my dissertation would be an impossible task without the kind support of
numerous people. First and foremost, I would like to thank my advisor Dr. Keith W.
Goyne and co-advisor Dr. Stephen H. Anderson. They have given me invaluable
knowledge on my coursework, research, and writing. They also made great efforts to
make sure I progressed towards my degree and became a better person. It has been an
honor to work with such wonderful mentors in my study.
I would also like to thank my other committee members, Dr. Chung-Ho Lin and
Dr. Robert Lerch. Dr. Lin has helped me many times in the lab trouble shooting
instruments and developing methods, and Dr. Lerch let me use his lab to conduct
experiments. I thank the University of Missouri Center for Agroforestry for funding my
research.
A number of people have helped me in my experiments in many ways. Amber
Spohn and Bettina Coggeshall helped me a lot regarding radioactive material waste
disposal. My lab mates Satchel Gaddie, Kristen Veum, Laura Gosen, and David Francis
offered me various types of help conducting my experiments.
On a personal level, I would like to thank my friends Sandeep, Anoma and
Bunjurluk for sharing knowledge, experience and information with me. Special thanks to
my family, my parents, my grandmother, and my husband Jerry. Their love and support
gave me the courage to pursue my dreams.

ii
TABLE OF CONTENTS

ACKNOWLEDGEMENTS..................................................................................................... ii
LIST OF FIGURES ............................................................................................................... vi
LIST OF TABLES ............................................................................................................... viii
ABSTRACT .......................................................................................................................... ix
Chapter 1 . Introduction 1
1.1 Introduction ....................................................................................................................... 1
1.2 Objectives ......................................................................................................................... 3
1.3 Studies .............................................................................................................................. 4
Chapter 2 . Literature Review 5
2.1 Use of Antibiotics in Animal Agriculture ........................................................................... 5
2.2 Presence of Antibiotics in the Environment and Potential Environmental Hazards ............. 6
2.3 Utilizing Vegetative Buffers to Mitigate Pollutant Transport .............................................. 8
2.4 Previous Studies Investigating Veterinary Antibiotic Sorption ........................................... 9
2.4.1 Factors affecting veterinary antibiotic persistence in soil ............................................. 9
2.4.2 Sorption concepts and terminology ........................................................................... 10
2.4.3 Sorption of Tetracyclines to soil................................................................................ 12
2.4.4 Sorption of Sulfonamides to soil ............................................................................... 14
2.4.5 Influence of dissolved organic matter on organic pollutant sorption........................... 17
2.5 Column Transport Experiments and Non-Equilibrium Modeling ...................................... 19
2.5.1 Column transport methodology ................................................................................. 19
2.5.2 Physical non-equilibrium transport models................................................................ 20
2.5.3 Chemical non-equilibrium and transport models ....................................................... 22
2.5.4 Findings from studies investigating VA transport in soil columns.............................. 23
2.6 Physicochemical Properties of the Veterinary Antibiotics Studied.................................... 25
2.6.1 Oxytetracycline ........................................................................................................ 25
2.6.2 Sulfadimethoxine and sulfamethazine ....................................................................... 26
REFERENCES ..................................................................................................................... 26
Chapter 3 . Veterinary Antibiotic Sorption to Agroforestry Buffer, Grass Buffer and Cropland
Soils 34
Abstract ................................................................................................................................ 34
3.1 Introduction ..................................................................................................................... 35
iii
3.2 Materials and Methods .................................................................................................... 39
3.2.1 Site history, soil sampling, and soil characterization .................................................. 39
3.2.2 Sorption studies ........................................................................................................ 41
3.2.3 Aqueous phase analyses ............................................................................................ 42
3.2.4 Mathematical description of sorption data ................................................................. 43
3.2.5 Statistical analyses .................................................................................................... 46
3.3 Results and Discussion .................................................................................................... 46
3.3.1 Adsorption and extraction isotherms ......................................................................... 46
3.3.2 Solid-solution partition coefficients (K ) ................................................................... 51
d
3.3.3 Correlation of sorption to soil properties ................................................................... 55
3.3.4 Mitigating veterinary antibiotic transport using vegetative buffer strips ..................... 61
3.4 Conclusions ..................................................................................................................... 62
REFERENCES ..................................................................................................................... 63
Chapter 4 . Sulfamethazine Sorption to Soil: Effects of Vegetative Management, pH, and
Dissolved Organic Matter 69
Abstract ................................................................................................................................ 69
4.1 Introduction ..................................................................................................................... 70
4.2 Materials and Methods .................................................................................................... 73
4.2.1 Sulfamethazine ......................................................................................................... 73
4.2.2 Manure-derived dissolved organic matter .................................................................. 74
4.2.3 Site details, soil sampling, and soil characterization .................................................. 75
4.2.4 Sorption experiments ................................................................................................ 79
4.2.5 Mathematical Description of Sorption Data ............................................................... 84
4.2.6 Statistical Analyses ................................................................................................... 86
4.3 Results and Discussion .................................................................................................... 87
4.3.1 SMZ Sorption in Absence of DOM ........................................................................... 87
4.3.2 Soil and Vegetative Effects on K and Correlation Analysis ...................................... 88
d
4.3.3 Influence of pH of SMZ sorption .............................................................................. 97
4.3.4 Effects of DOM ...................................................................................................... 100
4.3.5 Sulfamethazine desorption studies .......................................................................... 103
4.4 Conclusions ................................................................................................................... 106
REFERENCES ................................................................................................................... 107
Chapter 5 . Sulfamethazine Transport in Agroforestry and Cropland Soils 112
iv
Abstract .............................................................................................................................. 112
5.1 Introduction ................................................................................................................... 113
5.2 Model Theory................................................................................................................ 117
5.3 Materials and Methods .................................................................................................. 120
5.3.1 Soil sampling and DOM preparation ....................................................................... 120
5.3.2 Sorption isotherms .................................................................................................. 123
5.3.3 Soil columns ........................................................................................................... 125
5.3.4 Bromide tracer ........................................................................................................ 126
5.3.5 Sulfamethazine transport......................................................................................... 127
5.3.6 Sample analysis ...................................................................................................... 127
5.3.7 Parameter estimation .............................................................................................. 128
5.4 Results and Discussion .................................................................................................. 129
5.4.1 Sorption isotherms .................................................................................................. 129
5.4.2 Bromide transport ................................................................................................... 130
5.4.3 Sulfamethazine transport......................................................................................... 132
5.4.4 Modeling results ..................................................................................................... 135
5.4.5 Parameter estimation and DOM effects ................................................................... 138
5.5 Conclusions ................................................................................................................... 143
REFERENCES ................................................................................................................... 145
Chapter 6 . Conclusions 149
REFERENCES ................................................................................................................... 151
APPENDICES .................................................................................................................... 152
Appendix 1 ..................................................................................................................... 152
Appendix 2 ..................................................................................................................... 155
Appendix 3 ..................................................................................................................... 156
Appendix 4. .................................................................................................................... 157
Appendix 5 ..................................................................................................................... 158
Appendix 6 ..................................................................................................................... 159
Appendix 7 ..................................................................................................................... 160
Appendix 8 ...................................................................................................................... 161
Appendix 9 ...................................................................................................................... 162
VITA .................................................................................................................................. 163

v
LIST OF FIGURES
Figure 3.1 Oxytetracycline (OTC) adsorption/extraction to (a) Armstrong, (b)
Huntington, and (c) Menfro soils planted to maize/soybean rotation (Crop), grass
buffer strips (Grass), and agroforestry (tree/grass) buffer strips (AGF). Error bars,
where observed, represent the 95% confidence interval. ......................................... 48
Figure 3.2 (a) Oxytetracycline and (b) sulfadimethoxine solid-solution distribution
coefficients (K ) for Armstrong, Huntington, and Menfro soils at 0.10 mM initial
d
antibiotic concentration. Error bars, where observed, represent the 95% confidence
interval................................................................................................................... 53
Figure 3.3 Relationships between soil parameters and solid-solution distribution
coefficients (log K ) for (a) oxytetracycline and (b) sulfadimethoxine at 0.10 mM
d
initial antibiotic concentration. ............................................................................... 58
Figure 3.4 (a) Ionization of aqueous sulfadimethoxine and (b) distribution of cationic
(SDT+), zwitterionic (SDTo), and anionic (SDT-) sulfadimethoxine in aqueous
solution as a function of pH. .................................................................................. 59
Figure 4.1 (a) Chemical structure and (b) distribution of cationic (SMZ+), zwitterionic
(SMZo), and anionic (SMZ-) sulfamethazine in aqueous solution as a function of pH.
.............................................................................................................................. 73
Figure 4.2 sulfamethazine solid-solution distribution coefficients (K ) for Armstrong,
d
Huntington, and Menfro soils at (a) 0.0025 mM (b) 0.01 mM, (c) 0.018 mM, (d)
0.025 mM, and (e) 0.05 mM nitial concentration. Error bars, where observed,
represent the 95% confidence interval. ................................................................... 89
Figure 4.3 Sulfamethazine (SMZ) sorption to soil in presence and absence of dissolved
organic matter (DOM; 150 mg L-1 OC) to (a) Armstrong row-crop (RC), (b)
Armstrong grass buffer strip (GBS), (c) Armstrong agroforestry buffer strip (ABS),
(d) Huntington RC, (e) Huntington GBS, (f) Huntington ABS, (g) Menfro RC, (h)
Menfro GBS, and (i) Menfro ABS soils. Error bars, where observed, represent the
95% confidence interval. ........................................................................................ 93
Figure 4.4 Plot of predicted K using multiple regression model and experimental K
d d
with 95% confidence interval. ................................................................................ 94
Figure 4.5 Relationships between pH and solid-solution distribution coefficients (K ) for
d
sulfamethazine at (a) 0.0025 mM, and (b) 0.025 mM initial concentrations for the
Armstrong and Huntington grass buffer strip soils. K values collected from
d
sorption isotherm experiments at inherent pH values are provided for reference. ... 98
s
Figure 4.6 Sulfamethazine (SMZ) desorption isotherms for (a) Armstrong grass soil
without DOM, (b) Armstrong grass soil with DOM, (c) Huntington grass soil
without DOM, and (d) Huntington grass soil with DOM at initial concentrations
0.05 mM and 0.01 mM. ........................................................................................ 104
Figure 5.1 Sorption models. C is liquid phase with solute concentration C, S is an
1
instantaneous sorption site, S is a kinetic sorption site, and S is irreversible sorption
2 3
site. K is the solid to solution distribution coefficient, K and N are the Freundlich
d f
coefficient and exponent, respectively, α is the reversible adsorption/desorption
2
rate, and β is the irreversible adsorption rate. Black boxes indicate omission of
3
particular sorption sites. The model names reflect the number of sites, (S ), number
1–3
of rates (R ), sorption concept (lin: linear and Freu: Freundlich sorption isotherms)
0–2
vi
and reversibility of sorbate removal from a site (rev: reversible, irrev: irreversible).
Developed after Wehrhan et al. (2007). ................................................................ 121
Figure 5.2 Sulfamethazine (SMZ) sorption (S) to (a) Huntington agroforestry soil and (b)
Huntington cropland soil in absence and presence of dissolved organic matter
(DOM). Error bars, where observed, represent the 95% confidence interval. ........ 131
Figure 5.3 Bromide breakthrough curves for the agroforestry (AGF), agroforestry +
dissolved organic matter (AGF + DOM), and cropland (Crop) soil columns and
simulated fits obtained using a physical equilibrium model and the CXTFIT
software. (Please note that for the AGF + DOM column, DOM was only pulsed into
the column when SMZ was added.)...................................................................... 133
Figure 5.4 Sulfamethazine breakthrough curves for the agroforestry (AGF), agroforestry
and dissolved organic matter (AGF + DOM), and cropland (Crop) soil columns. . 134
Figure 5.5 Two-site, one-rate (2S1R) models for sulfamethazine breakthrough curves in
(a) agroforestry soil, (b) agroforestry soil with DOM and (c) cropland soil. The
model names reflect sorption concept (lin: linear and Freu: Freundlich sorption
isotherms) and reversibility of sorbate removal from a site (rev: reversible, irrev:
irreversible). ........................................................................................................ 139
Figure 5.6 Two-site, two-rate (2S2R) models for sulfamethazine breakthrough curves in
(a) agroforestry soil, (b) agroforestry soil with DOM and (c) cropland soil. The
model names reflect sorption concept (lin: linear and Freu: Freundlich sorption
isotherms) and reversibility of sorbate removal from a site (rev: reversible, irrev:
irreversible). ........................................................................................................ 140
Figure 5.7 Three-site, two-rate (3S2R) models for sulfamethazine breakthrough curves in
(a) agroforestry soil, (b) agroforestry soil with DOM and (c) cropland soil. The
model names reflect sorption concept (lin: linear and Freu: Freundlich sorption
isotherms) and reversibility of sorbate removal from a site (rev: reversible, irrev:
irreversible). ........................................................................................................ 141

vii
LIST OF TABLES

Table 3.1 Selected properties of the veterinary antibiotics studied . ............................... 38
Table 3.2 Mean soil characterization data for soils collected from three soil series planted
to agroforestry and grass buffer strips and cropland. ............................................... 44
Table 3.3 Freundlich model parameters for oxytetracycline adsorption and extraction
isotherms and associated hysteresis index (HI) values. ........................................... 50
Table 3.4 Analysis of variance results indicating the effect of soil and vegetation
management factors and their interaction on solid to solution partition coefficients
(K ) for oxytetracycline (OTC) at varying initial concentrations. ............................ 52
d
Table 3.5 Linear correlation coefficients between oxytetracycline (OTC) and
sulfadimethoxine (SDT) solid to solution partition coefficients (log Kd) and soil
properties ............................................................................................................... 57
Table 4.1 Mean soil characterization data for soils collected from three soils planted to
agroforestry (ABS) and grass buffer strips (GBS) and row crops (RC). .................. 80
Table 4.2 Mean Freundlich model parameters for sulfamethazine adsorption to row-crop
(RC), grass buffer strip (GBS), and agroforestry buffer strip (ABS) soils in presence
and absence of DOM (150 mg L-1 OC). The 95% confidence intervals (CI)
surrounding the mean values are presented as are correlation coefficients (r2) and the
number of samples (n) included in the regression analyses. .................................... 95
Table 4.3 Adsorption coefficients for sulfamethazine adsorption at multiple initial
concentrations to row-crop (RC), grass buffer strip (GBS), and agroforestry buffer
strip (ABS) soils in presence and absence of DOM (150 mg L-1 OC). The 95%
confidence intervals (CI) surrounding the mean values are presented. .................... 96
Table 4.4 Analysis of variance results indicating the effects of soil, vegetative
management, DOM, and interactions of these factors on sulfamethazine (SMZ) solid
to solution partition coefficients (K ) at varying initial concentrations. ................. 102
d
Table 4.5 Linear correlation coefficients between sulfamethazine (SMZ) solid to solution
partition coefficients (log K ) and soil properties obtained at an initial SMZ
d
concentration of 0.010 mM . ................................................................................ 102
Table 4.6 Hysteresis indices (HI) of Armstrong grass soil and Huntington grass soil at
initial concentrations of 0.05 mM and 0.01 mM with and without dissolved organic
matter (DOM). ..................................................................................................... 105
Table 5.1 Mean soil characterization data for Huntington soil collected from locations
planted to agroforestry (AGF) and cropland treatments. ....................................... 122
Table 5.2 Selected chemical properties of sulfamethazine. .......................................... 123
Table 5.3 Experimental conditions used in the saturated column experiments. ............ 126
Table 5.4 Model efficiency (EF), eluted mass (EM), and fitted parameters of different
isotherm-based models obtained by HYDRUS-1D for three sulfamethazine columns.
............................................................................................................................ 144

viii
ABSTRACT

Veterinary antibiotics (VAs) such as oxytetracycline (OTC), sulfadimethoxine
(SDT) and sulfamethazine (SMZ) may adversely impact human health and environmental
quality. Understanding sorption and transport of VAs is important for assessing the risk
of VAs reaching surface or groundwater resources. Vegetative buffer strips (VBS) affect
soil properties that enhance removal of organic pollutants and thus may be a useful tool
for mitigating veterinary antibiotic transport from agricultural lands. Therefore, the
objectives of this study were: (1) measure the sorption and retention of veterinary
antibiotics to soils collected from three different soils series each planted to agroforestry
buffer (AGF), grass buffer (GBS), and row crops (RC), and determine the soil physical
and chemical properties governing antibiotic sorption to these soils; (2) investigate
changes in VA sorption and retention to VBS and cropland soils in the presence of
manure-derived dissolved organic matter (DOM); (3) and study and model VA transport
through soil columns repacked with VBS and cropland soils in presence and absence of
manure-derived DOM. Sorption experiment results show that OTC was strongly
adsorbed by all soils and was not readily extractable, whereas SDT and SMZ sorption to
soils were weak and therefore highly mobile in soils. The sorption isotherms for OTC and
SMZ were well fitted by the Freundlich isotherm model. Further investigation of solid-to-
solution partition coefficients (K ) revealed that vegetative management had a significant
d
(P < 0.01) influence on SMZ sorption and followed the order AGF > GBS > RC, and for
OTC sorption VBS > RC. Significant differences in K values for these VAs were also
d
noted among the soil series studied. Linear regression analyses indicate that clay content
and pH were the most important soil properties controlling OTC and SDT adsorption,
ix