In soils spiked with gamma-HCH & DDT, and transplanted with wheat, the differences of gamma-HCH between the rhizosphere and non-rhizosphere soils increased with time, reached the peak on 30th sampling day, and then decreased with time. In the rhizosphere and non-rhizosphere soils, pp'-DDE/SigmaDDTs, op'-DDD/SigmaDDTs and pp'-DDD/SigmaDDTs increased with time; whilst op'-DDT/SigmaDDT and pp'-DDT/SigmaDDT decreased with time. The wheat, corn and soybean rhizosphere soils differed greatly in soil properties, but it was hard to conclude the effect of crop roots on the variation in concentration of gamma-HCH, p,p'-DDE, p,p'-DDD and p,p'-DDT in the rhizosphere soils except for root accumulation and translocation. / In the control, wheat and corn rhizosphere soils, the n-hexane extracted fraction of gamma-HCH, DDE, DDD and DDT decreased with time whereas the hexane/acetone extracted fraction increased with time after the 20th sampling day. The n-hexane extracted forms were higher in the rhizosphere soils than those in the non-rhizosphere soils, while the hexane/acetone extracted forms were lower in the rhizosphere soils than in the non-rhizosphere soils. / In the wheat, corn rhizosphere soils and the control, the concentration of NO3-N showed a significant negative correlation with n-hexane extracted DDE, DDD and DDT residues and a significant positive correlation with hexane/acetone extracted residues. The concentration of ammonium nitrogen (NH4-N) showed a significant negative correlation with hexane extracted gamma-HCH, DDE, DDD and DDT residues in the control, corn and wheat rhizosphere soils: but only had significant positive correlation with the n-hexane/acetone extracted fraction in the corn rhizosphere soil. The positive correlations between the n-hexane extracted residues of the target pesticides and soil OC were seldom significant in the control, sometimes significant in the wheat rhizosphere soils, and always strong and significant in the corn rhizosphere soils. The correlation of the n-hexane/acetone extracted residues with soil OC was positive and sometimes significant in the wheat rhizosphere soils, and significant and negative in the corn rhizosphere soils. The results indicated that the concentrations of different OCPs extracted from were strongly influenced by nutritional conditions and soil organic carbon. / Organic carbon (OC), dissolved organic carbon (DOC) and cultivation period were tested to explore their potential effects on target OCPs in the rhizosphere soils. The concentration of the target OCPs in the wheat rhizosphere soils increased proportionally to soil OC, whilst the uptake of OCPs by wheat roots and further translocation to the aboveground part were inversely proportional to soil OC. DOC only showed a negative correlation with concentration of p,p'-DDE and p,p'-DDT in the corn rhizosphere soils. After a longer root-soil interaction, roots had a more significant effect on the concentration of OCPs in the rhizosphere soils closer to the root surface. / The variation of different forms of OCPs in rhizosphere soils and their relationships with nitrogen nutrients and organic carbon were studied. / Variations in concentrations of organochlorine pesticide (OCP) residues in the rhizosphere soils were evaluated using rhizoboxes. A sequential extraction method was developed to study the fractionation and extractability of OCPs in rhizosphere soils. The key findings are as follows: / Zhu Xuemei. / "September 2006." / Adviser: Kin Che Lam. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1532. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 265-288). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Wai Lok Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 142-155). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstracts --- p.ii / Contents --- p.vii / List of figures --- p.xiii / List of tables --- p.xvi / Abbreviations --- p.xviii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Pentachlorophenol / Chapter 1.1.1 --- Applications of pentachlorophenol --- p.1 / Chapter 1.1.2 --- Characteristics --- p.3 / Chapter 1.1.3 --- Pentachlorophenol in the environment --- p.3 / Chapter 1.1.4 --- Toxicity of Pentachlorophenol --- p.6 / Chapter 1.2 --- Treatments of Pentachlorophenol --- p.10 / Chapter 1.2.1 --- Physical treatment --- p.10 / Chapter 1.2.2 --- Chemical treatment --- p.11 / Chapter 1.2.3 --- Biological treatment --- p.13 / Chapter 1.3 --- Biodegradation --- p.14 / Chapter 1.3.1 --- Biodegradation of PCP by bacteria --- p.14 / Chapter 1.3.2 --- Biodegradation of PCP by white-rot fungi --- p.15 / Chapter 1.4 --- Biosorption --- p.24 / Chapter 1.5 --- Proposed Strategy --- p.28 / Chapter 1.6 --- Spent Mushroom Compost / Chapter 1.6.1 --- Background --- p.28 / Chapter 1.6.2 --- Physico-chemical properties of SMC --- p.29 / Chapter 1.6.3 --- As a biosorbent --- p.29 / Chapter 1.6.3.1 --- Factors affecting biosorption --- p.31 / Chapter 1.6.3.2 --- Contact time --- p.31 / Chapter 1.6.3.3 --- Initial pH --- p.32 / Chapter 1.6.3.4 --- Concentration of biosorbent --- p.33 / Chapter 1.6.3.5 --- Initial PCP concentration --- p.34 / Chapter 1.6.3.6 --- Incubation temperature --- p.34 / Chapter 1.6.3.7 --- Agitation speed --- p.35 / Chapter 1.6.4 --- Modeling of adsorption --- p.36 / Chapter 1.6.4.1 --- Langmuir isotherm --- p.36 / Chapter 1.6.4.2 --- Freundlich isotherm --- p.36 / Chapter 1.6.5 --- As a source of PCP-degrading bacteria --- p.38 / Chapter 1.6.5.1 --- Identification of PCP-degrading bacterium --- p.40 / Chapter 1.6.6 --- As a source of fungus --- p.42 / Chapter 1.7 --- Objectives of this Study --- p.43 / Chapter 2. --- Materials and Methods --- p.44 / Chapter 2.1 --- Spent Mushroom compost (SMC) Production --- p.44 / Chapter 2.2 --- Characterization of SMC --- p.46 / Chapter 2.2.1 --- pH --- p.46 / Chapter 2.2.2 --- Electrical conductivity --- p.46 / Chapter 2.2.3 --- "Carbon, hydrogen, nitrogen and sulphur contents" --- p.46 / Chapter 2.2.4 --- Infrared spectroscopic study --- p.47 / Chapter 2.2.5 --- Metal analysis --- p.47 / Chapter 2.2.6 --- Anion content --- p.47 / Chapter 2.2.7. --- Chitin assay --- p.48 / Chapter 2.3 --- Extraction of PCP --- p.49 / Chapter 2.3.1 --- Selection of extraction solvent --- p.49 / Chapter 2.3.2 --- Selection of desorbing agent --- p.49 / Chapter 2.3.3 --- Extraction efficiency --- p.50 / Chapter 2.4 --- Adsorption of Pentachlorophenol on SMC --- p.50 / Chapter 2.4.1 --- Preparation of pentachlorophenol (PCP) stock solution --- p.50 / Chapter 2.4.2 --- Batch adsorption experiment --- p.51 / Chapter 2.4.3 --- Quantification of PCP by HPLC --- p.51 / Chapter 2.4.4 --- Data analysis for biosorption --- p.51 / Chapter 2.4.5 --- Optimization of PCP adsorption --- p.52 / Chapter 2.4.5.1 --- Effect of contact time --- p.52 / Chapter 2.4.5.2 --- Effect of initial pH --- p.52 / Chapter 2.4.5.3 --- Effect of incubation temperature --- p.53 / Chapter 2.4.5.4 --- Effect of shaking speed --- p.53 / Chapter 2.4.5.5 --- Effect of initial PCP concentration and amount of biosorbent --- p.53 / Chapter 2.4.6 --- Adsorption isotherm --- p.53 / Chapter 2.4.7 --- Effect of removal efficiency on reuse of biosorbent --- p.54 / Chapter 2.5 --- Biodegradation by Isolated Bacterium --- p.54 / Chapter 2.5.1 --- Isolation of PCP-tolerant bacteria from mushroom compost --- p.54 / Chapter 2.5.2 --- Screening for the best PCP-tolerant bacterium --- p.54 / Chapter 2.5.3 --- Identification of the isolated bacterium --- p.55 / Chapter 2.5.3.1 --- 16S ribosomal DNA sequencing --- p.55 / Chapter 2.5.3.1.1 --- Extraction of DNA --- p.55 / Chapter 2.5.3.1.2 --- Specific PCR for 16S rDNA --- p.56 / Chapter 2.5.3.1.3 --- Gel electrophoresis --- p.57 / Chapter 2.5.3.1.4 --- Purification of PCR products --- p.57 / Chapter 2.5.3.1.5 --- Sequencing of 16S rDNA --- p.58 / Chapter 2.5.3.2 --- Gram staining --- p.60 / Chapter 2.5.3.3 --- Biolog Microstation System --- p.60 / Chapter 2.5.3.4 --- MIDI Sherlock Microbial Identification System --- p.61 / Chapter 2.5.4 --- Optimization of PCP degradation by PCP-degrading bacterium --- p.62 / Chapter 2.5.4.1 --- Effect of incubation time --- p.63 / Chapter 2.5.4.2 --- Effect of shaking speed --- p.63 / Chapter 2.5.4.3 --- Effect of initial PCP concentration and inoculum size --- p.63 / Chapter 2.5.4.4 --- Study of PCP degradation pathway by isolated bacterium using GC-MS --- p.64 / Chapter 2.6 --- Biodegradation by Fungus Pleurotus pulmonarius --- p.64 / Chapter 2.6.1 --- Optimization of PCP degradation by P. pulmonarius --- p.65 / Chapter 2.6.1.1 --- Effect of incubation time --- p.65 / Chapter 2.6.1.2 --- Effect of shaking speed --- p.65 / Chapter 2.6.1.3 --- Effect of initial PCP concentration and inoculum size --- p.65 / Chapter 2.6.2 --- Study of PCP degradation pathway by fungus using GC-MS --- p.65 / Chapter 2.6.3 --- Specific enzyme assays --- p.66 / Chapter 2.6.3.1 --- Extraction of protein and enzymes --- p.66 / Chapter 2.6.3.2 --- Protein --- p.66 / Chapter 2.6.3.3 --- Laccase --- p.67 / Chapter 2.6.3.4 --- Manganese peroxidase (MnP) --- p.67 / Chapter 2.6.4 --- Microtox® assay --- p.67 / Chapter 2.7 --- Statistical Analysis --- p.68 / Chapter 3. --- Results --- p.69 / Chapter 3.1 --- Physico-chemical Properties of SMC --- p.69 / Chapter 3.2 --- Extraction Efficiency and Desorption Efficiency of PCP --- p.69 / Chapter 3.3 --- Batch Adsorption Experiments --- p.76 / Chapter 3.3.1 --- Optimization of adsorption conditions --- p.76 / Chapter 3.3.1.1 --- Effect of contact time --- p.76 / Chapter 3.3.1.2 --- Effect of initial pH --- p.76 / Chapter 3.3.1.3 --- Effect of shaking speed --- p.79 / Chapter 3.3.1.4 --- Effect of incubation temperature --- p.79 / Chapter 3.3.1.5 --- Effect of initial PCP concentration and amount of biosorbent --- p.79 / Chapter 3.3.2 --- Reuse of SMC --- p.83 / Chapter 3.3.3 --- Isotherm plot --- p.83 / Chapter 3.4 --- Biodegradation by PCP-degrading Bacterium --- p.86 / Chapter 3.4.1 --- Isolation and purification of PCP-tolerant bacteria --- p.86 / Chapter 3.4.2 --- Identification of the isolated bacterium --- p.90 / Chapter 3.4.2.1 --- 16S rDNA sequencing --- p.90 / Chapter 3.4.2.2 --- Gram staining --- p.90 / Chapter 3.4.2.3 --- Biolog MicroPlates Identification System --- p.90 / Chapter 3.4.2.4 --- MIDI Sherlock Microbial Identification System --- p.90 / Chapter 3.4.3 --- Growth curve of PCP-degrading bacterium --- p.90 / Chapter 3.4.4 --- Optimization of PCP degradation by PCP-degrading bacterium --- p.97 / Chapter 3.4.4.1 --- Effect of incubation time --- p.97 / Chapter 3.4.4.2 --- Effect of shaking speed --- p.97 / Chapter 3.4.4.3 --- Effect of initial PCP concentration and inoculum size of bacterium --- p.101 / Chapter 3.4.5 --- Determination of breakdown products of PCP by PCP-degrading bacterium --- p.101 / Chapter 3.5 --- Biodegradation by Fungus Pleurotus pulmonarius --- p.103 / Chapter 3.5.1 --- Growth curve of P. pulmonarius --- p.103 / Chapter 3.5.2 --- Optimization of PCP degradation by P. pulmonarius --- p.103 / Chapter 3.5.2.1 --- Effect of incubation time --- p.103 / Chapter 3.5.2.2 --- Effect of shaking speed --- p.103 / Chapter 3.5.2.3 --- Effect of initial PCP concentration and inoculum size of fungus --- p.108 / Chapter 3.5.3 --- Determination of breakdown products of PCP by P. pulmonarius --- p.108 / Chapter 3.5.4 --- Enzyme assays --- p.108 / Chapter 3.6 --- Integration of Biosorption by SMC and Biodegradation by P. pulmonarius --- p.112 / Chapter 3.6.1 --- Evaluation of PCP removal by an integration system --- p.112 / Chapter 3.6.2 --- Evaluation of toxicity by Micortox® assays --- p.112 / Chapter 4. --- Discussion --- p.115 / Chapter 4.1 --- Physico-chemical Properties of SMC --- p.115 / Chapter 4.2 --- Extraction Efficiency and Desorption Efficiency of PCP --- p.116 / Chapter 4.3 --- Batch Biosorption Experiment --- p.117 / Chapter 4.3.1 --- Effect of contact time --- p.117 / Chapter 4.3.2 --- Effect of initial pH --- p.118 / Chapter 4.3.3 --- Effect of shaking speed --- p.120 / Chapter 4.3.4 --- Effect of incubation temperature --- p.120 / Chapter 4.3.5 --- Effect of initial PCP concentration and amount of biosorbent --- p.121 / Chapter 4.3.6 --- Reuse of SMC --- p.122 / Chapter 4.3.7 --- Modeling of biosorption --- p.122 / Chapter 4.4 --- Biodegradation of PCP by PCP-degrading Bacterium --- p.124 / Chapter 4.4.1 --- Isolation and purification of PCP-tolerant bacterium --- p.124 / Chapter 4.4.2 --- Identification of the isolated bacterium --- p.125 / Chapter 4.4.3 --- Optimization of PCP degradation by PCP-degrading bacterium --- p.126 / Chapter 4.4.3.1 --- Effect of incubation time --- p.126 / Chapter 4.4.3.2 --- Effect of shaking speed --- p.128 / Chapter 4.4.3.3 --- Effect of initial PCP concentration and inoculum size of bacterium --- p.128 / Chapter 4.4.4 --- PCP degradation pathway by S. marcescens --- p.129 / Chapter 4.5 --- Biodegradation of PCP by Pleurotus pulmonarius --- p.130 / Chapter 4.5.1 --- Optimization of PCP degradation by P. pulmonarius --- p.130 / Chapter 4.5.1.1 --- Effect of incubation time --- p.131 / Chapter 4.5.1.2 --- Effect of shaking speed --- p.131 / Chapter 4.5.1.3 --- Effect of initial PCP concentration and inoculum size of fungus --- p.131 / Chapter 4.5.2 --- Enzyme activities --- p.132 / Chapter 4.5.3 --- PCP degradation pathway by P. pulmonarius --- p.133 / Chapter 4.6 --- Comparison of PCP Degradation between S.marcescens and P. pulmonarius --- p.133 / Chapter 4.7 --- Integration of Biosorption by SMC and Biodegradation by P. pulmonarius --- p.135 / Chapter 4.8 --- Evaluation of toxicity by Microtox® assay --- p.135 / Chapter 4.9 --- Comparison of PCP Removal by Integration System of Sorption and Fungal Biodegradation and Conventional Treatments --- p.136 / Chapter 4.10 --- Further Investigations --- p.137 / Chapter 5. --- Conclusion --- p.139 / Chapter 6. --- References --- p.142

Graduation date: 1996

Groundwater contamination on irrigated land is of concern in this nation and around the world. In order to reduce the potential of groundwater contamination by agricultural practices such as irrigation, fertilizer and pesticide application, vadose-zone monitoring and sampling are needed. The main objective of this study was to evaluate impacts of current irrigation treatments and soil structures on the migration of pollutants to groundwater. Passive CAPillary wick pan Samplers (PCAPS) and suction cups were installed in two cracking clays and one sandy soil under the pear tree root zone. PCAPS and suction cups were used to collect nitrate-nitrogen and tracer samples. Tracers were applied to track the spatial and temporal patterns of compounds that mimic nitrate-nitrogen and pesticide movement. The observed magnitude of water leaching over 3 months differed between irrigation methods and soil structures and decreased in this order: flooding over 3 months in clay soil (22.8 cm) > micro-sprinkler in clay soil (16.1 cm) > over-head sprinkler in sandy soil (4.1 cm). Leaching patterns were varied spatially; soil structures, irrigation methods, preferential flow, and high water table may have been responsible for the spatial variation of leaching. Mass recovery of all three tracers, including bromide, blue dye, and rhodamine had the same decreasing order: flooding in clay soil > micro-sprinkler in clay soil > over-head sprinkler in sandy soil. Average blue dye and rhodamine concentrations had the following order: flooding in clay soil > micro-sprinkler in clay > over-head sprinkler in sandy soil. Since blue dye and rhodamine have similar properties to some moderately adsorbed pesticides, we may infer that the risk of pesticide movement in three sites should also decrease in this order. Presumably pesticide movement in clay soil would have been more pronounced for flooding than sprinkler irrigation. On the annual/seasonal basis, the total mass of nitrate-nitrogen leaching differed between irrigation methods and soil structures and decreased in the following order: over-head sprinkler in sandy soil > flooding in clay soil > micro-sprinkler in clay soil. The annual average nitrate-nitrogen concentration observed under over-head sprinkler in sandy soil was 15 mg/l over the maximum allowed concentration level (10 mg/l) by the EPA while seasonal nitrate-nitrogen concentration was low in clay soil under current irrigation practices. Strong evidence suggested the occurrence of preferential flow in this study. Preferential flow may contribute to high water leachate, nitrate and pesticide migration. High correlation coefficients between paired PCAPS indicated that PCAPS have similar responses to water and solute leaching. Several improvements in PCAPS are needed to obtain representative samples under severe flooding conditions. Limited data suggested that ultra-low rate irrigation devices could reduce the water leaching and the potential of pollutant migration to the groundwater because ultra-low rate application devices minimize the soil macropore flow. / Graduation date: 1995

The use of agricultural chemicals often results in water pollution. This research, comprising three parts, was designed to investigate the role of soil and grass strips and water table management in reducing pesticide and nitrate residues in drainage waters. / The first part of the research was made on lysimeters to investigate the effects of soil and grass cover under two water table management regimes. Four treatments were involved: subsurface drainage, controlled drainage, grass cover, and bare soil. Each treatment consisted of three replicates. Contaminated water containing atrazine, metolachlor, and metribuzin residues was applied to the lysimeters and samples of drain effluent were collected. Significant reductions in pesticide concentrations were found in all treatments. / In the first year (1993), herbicide levels were reduced significantly, from an average of 250 mug/L to less than 10 mug/L. In the second year (1995), water polluted at a concentration of 50 mug/L, was applied to the lysimeters, and herbicide residues were reduced significantly to less than 1 mug/L. Subsurface drainage and grass cover lysimeters (SDG treatment) reduced herbicide concentration levels to a greater extent than the other treatments and the controlled drainage lysimeters reduced nitrate concentration levels to a greater extent than the free drainage lysimeters. / The second part of the research was a field study that reports the development and testing of an on-farm pollution control system using soil as a biological filter for trapping herbicide residues. A field site with four shallow surface ditches, underlain with four perforated drain pipes, was used to carry-out field measurements. Polluted water with concentration levels of 30 mg/L of nitrate and 100 mug/L of three commonly-used herbicides was applied to the ditches for 10 days continuously; and no water was applied for the following ten days. This cycle was repeated three times. Water samples were collected both before application and after the water came out of the drains. Herbicide levels were reduced significantly in drainage waters. The average concentration level of nitrate in drainage water was found to be 17 mg/L in comparison to 30 mg/L in applied water. Also, the bio-degradation of herbicide residues in the soil was found to occur between water applications. Thus, it appears that the system would be self-sustainable in the long term. / The third part of the research utilizes a water table model, DRAINMOD, for simulating drainage waters from agricultural land and a solute transport model, PRZM2, for simulating pesticide concentrations in the drain effluent coming out of the grass filter area. DRAINMOD was used to estimate the daily drain outflows that would occur in a 100 ha subsurface drained field in the for a 1-in-20 year annual rainfall period. It was found that 6% of the farm area could be used to bring down the concentrations in drainage water from 50 mug/L to less than 1 mug/L for the three herbicides. (Abstract shortened by UMI.)

A large number of man-made chemicals are present in the environment as pollutants and are capable of disrupting the endocrine system of animals and humans. Small-sized industry is an area where such chemicals are used and produced in abundance. There is no legislation governing the use, production and disposal of such chemicals, which studies have shown are posing a hazard to workers themselves and the surrounding communities. Run off water from seven sites in an area in Pretoria West, with significant numbers of small-sized industries, was screened for oestrogenicity, using the Recombinant Yeast Cell Bioassay (RCBA). Chemical analyses were done for the presence of endocrine disrupting chemicals (EOCs), including p-nonylphenol (p-NP), bisphenol A (BPA), phthalate esters, polychlorinated biphenyls (PCBs) and various organochlorine pesticides, including dichlorodiphenyltrichloroethane (DDT). The p-NP, PCBs and organochlorine pesticides were detected using a South African Bureau of Standards (SABS) in-house method: AM178 and the time of flight spectrometer, while the BPA and phthalates were detected using the CSIR Biochemtek Laboratory in-house GC-MS method: AM 186 based on the US EPA 8260 and the gas chromatography-mass spectrometer. The water tested positive for oestrogenic activity at all the sample sites and a significant amount of lindane, an organochlorine pesticide, was detected at one site. p-NP as well as phthalate esters were identified at different sites. No pattern or relationship could be established between the oestrogenic activity and the subsequent endocrine disrupting chemicals tested for. These EOCs in the water could pose a health risk for humans and animals. Further specific studies are needed to establish the possible sources of these contaminants, from industry and households. / Dissertation (MMed)--University of Pretoria, 2005. / School of Health Systems and Public Health (SHSPH) / Unrestricted

No description available.

No description available.

This report includes the determination of activity and possible mode of action for a group of potential new insecticides. The biological screening procedure was developed using Drosophila melanogaster as the test organism while Musca domestica was used for mode of action assays. The percent kill for each compound is based on the number of eggs placed on media containing the insecticide minus the number of adults enclosed as compared to the control media reared flies. Observations were made on all stages from eggs through adults to determine time of death and if any malformations were present. These observations aided in the mode of action studies as did preciously published work on diflurbenzuron. The mode of action studies encompassed chitin synthesis, chitin breakdown and DNA synthesis. Cuticle deposition was determined gravimetrically on pupal instar reared on media with and without DOWCO 416. Chitin synthesis and DNA synthesis were followed by measuring the incorporation of radiolabeled precursors by pupal instars reared on media with and without DOWCO 416. Chitin breakdown was followed through the measurement of chitinase activity spectrophotometrically on all stages of larvae which were reared on media with and without DOWCO 416. Direct inhibition of chitinase was investigated by incubation of the purified chitinase from Staphlycoccus griseus with varying concentrations of the test compound.

A field scale model for predicting the surface losses of pesticides (Pesticide Losses In Erosion and Runoff Simulator, PLIERS) was developed. PLIERS accounts for pesticide losses by degradation and volatilization, the washoff of pesticides from plant canopy and surface residue, the adsorption and desorption of pesticides to and from soil particles, and the movement of pesticides in the dissolved and adsorbed phases. Hydrologic data are generated by the comprehensive watershed model, FESHM; which contains an extended sediment detachment and transport algorithm. PLIERS uses first order rate equations to describe degradation and volatilization, and pesticide washoff. The adsorption of pesticides to individual particle size classes is estimated using the Freundlich equation. Movement of atrazine and 2,4-D in runoff and sediment was measured on twelve field plots under simulated rainfall. The plots were treated with conventional or no-tillage in combination with one of three residue levels (0, 750, and 1500 kg/ha). Runoff and sediment losses were found to increase with decreasing residue cover for both tillage systems. No-till reduced sediment loss and total runoff volume by 98 and 92 percent, respectively, compared to conventional tillage. Concentrations of atrazine and 2,4-D ir1 runoff and sediment were greater from the no-till plots than from the conventional plots but the total losses were less. Both pesticides were carried predominately in the dissolved phase. Averaged over all plots, the atrazine losses were 2.9 percent of applied amount for conventional tillage and 0.3 percent for no-tillage. The corresponding values for 2,4-D were 0.3 percent and 0.02 percent. PLIERS was validated using data from the rainfall simulator field plot studies. Agreement between predicted and observed data was very good for dissolved pesticide losses and satisfactory for adsorbed pesticide losses. In addition, the effects of tillage type and residue level were reflected in PLIERS predictions. PLIERS shows great potential as a flexible planning tool since it could be used with any comprehensive hydrologic model and is able to predict the losses of pesticides under various field conditions. / Master of Science