Dissipation and Leachability of Formulated Chlorpyrifos and Atrazine in Organically-amended Soils by Yunxiang Xiao Dissertation submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Entomology Approved by: Dr. Donald E. Mullins, ENT, Chairman Dr. Duane F. Berry, CSES Dr. Jeffrey R. Bloomquist, ENT Dr. Glen H. Hetzel, BSE Dr. Douglas G. Pfeiffer, ENT December, 1997 Blacksburg, Virginia Key words: Atrazine, Chlorpyrifos, Bioremediation,Extractability, Leachability Copyright 1997, Yunxiang Xiao Dissipation and Leachability of Formulated Chlorpyrifos and Atrazine in Organically-amended Soils Yunxiang Xiao Dr. Donald E. Mullins, Chairperson Department of Entomology (ABSTRACT) Bioremediation was studied in soils containing high concentrations of formulated chlorpyrifos (5 mg kg-1 Dursban® 4E) and atrazine (5 mg kg-1 AAtrex® 4L) using amendments including lignocellulosic sorbents, microbial nutrients (vegetable oil, corn meal and fertilizers), and microbial extracts from organic media previously exposed to these pesticides (chlorpyrifos and atrazine, respectively). Radiolabeled atrazine was used to examine the various dissipation routes in contaminated soil, also amended with lignocellulosic sorbents and microbial nutrients. Both chlorpyrifos and atrazine dissipation from contaminated soils was enhanced by organic-based material amendments. The half-lives of chlorpyrifos based on extractability for soils unamended and amended with vegetable oil and peat moss were 87 and 52 days, respectively. The half-lives of atrazine in unamended and amended soil (vegetable oil, peat moss and fertilizers) were 175 and 40 days, respectively. The leachability of chlorpyrifos from contaminated soil was dramatically reduced by 82% during the first 30 days of incubation in treatments amended with vegetable oil and peat moss while only a 28% of reduction in leachability occurred in the corresponding unamended controls. Only a slight reduction of atrazine leachability was detected in amended treatments after 120 days of incubation. Differences were found in the leachability of chlorpyrifos and atrazine when they were applied to soil either as technical grade or formulated material. The presence of surfactants and other adjuvants in formulated chlorpyrifos (Dursban® 4E) reduced chlorpyrifos leachability in contaminated soil. Chlorpyrifos leachability was reduced by 43% in the formulated chlorpyrifos treatments, whereas there was a negligible decrease in technical chlorpyrifos treated soil during the first 3 days after contamination. Atrazine extractability and leachability was not affected by its formulation (AAtrex® 4L). Amendments with lignocellulosic sorbents and nutrients decreased atrazine’s volatility from contaminated soils. After 16 weeks of incubation, less than 1% of 14C- atrazine was volatilized from incubated soils. Overall, after 16 weeks of incubation less than 4% of 14C-atrazine was mineralized and more radioactivity was recovered from 14 amended treatments than unamended treatments as CO2. The major portion of radioactivity (62%) was associated with physisorbed atrazine represented by the ethylacetate extract I from unamended treatments while only 28% of initial applied radioactivity was recovered in the corresponding amended treatments. Based on the sum of radioactivity in humic and fulvic acids, approximately 14% of radioactivity was incorporated or chemisorbed atrazine and its metabolites in both unamended and amended treatments. Forty-five percent of the initially applied radioactivity was associated with alkali insoluble fraction in amended treatments but only 17% of the initially applied radioactivity was detected in the corresponding unamended treatments. Less than 2 % of initial activity associated with physisorbed portions of fulvic acids and alkaline insoluble fraction indicated as the radioactivity in methylene chloride and ethylacetate extract II . Over time, more radioactivity was associated with polar atrazine hydroxylated degradation products. iii ACKNOWLEDGMENTS I would like to extend my sincere gratitude to Dr. Donald E. Mullins for his guidance and enormous assistance concerning my research and education at Virginia Tech. I also appreciate the financial support of my research for my graduate study which he provided. I appreciate assistance and guidance from my committee, Drs. Duane F. Berry, Jeffrey R. Bloomquist, Glen H. Hetzel, and Douglas G. Pfeiffer for my research and education. I thank Dr. Duane F. Berry especially for his assistance and discussions in designing and analyzing the 14C-atrazine remediation study. Dr. Jeffrey R. Bloomquist was my greatest mentor for three courses during pursuit of my degree. He deserves my sincere appreciation. It is always enjoyable and beneficial to discuss matters with him. I also would like to extend my sincere appreciation to Drs. Glen H. Hetzel and Douglas G. Pfeiffer for their assistance in editing my draft manuscripts, they did some extra advisory work! Over months, I have worked at the Pesticide Research Laboratory in the Biochemistry Department. I thank Mr. Roddy Young for his generosity in providing me access to equipment and the laboratory for conducting a major part of my research. It was always enjoyable working in his lab. Many thanks go to the people at the Pesticide Research Laboratory: Ms. Joy Burroughs, Mr. David Ruggio, Ms. Jean McCarthy, and Ms. Sandra Gabbert. It was my pleasure to talk with David Ruggio about music, Chinese culture, and many other things. An enormous amount of technical assistance was provided to me by Keith Tignor who helped me in completing several of my research projects. His helpful suggestions and advice contributed greatly to my success. I appreciate his assistance over the years. One of my greatest achievements has been learning more about American culture. I owe much of this to the graduate students in the Department. I would especially like to thank David Judge, Jarrod Leland, Tom Kuhar, and many others for their friendships and sincere assistance when I was in need. iv Appreciation also goes to Ali and Tom Wieboldt, for being our friends and for their enormous assistance in editing my dissertation. I deeply appreciate their friendship and assistance in polishing this finally product. My wife, parents, parents-in-law, my sisters and brother have always encouraged my endeavors for high achievements. I owe them so much for their support and understanding. Without their support, the completion of this dissertation would not be possible. I appreciate enormous sacrifice and hard work from my lovely wife Wenkai during this endeavor. I also would like to apologize to my dearest daughter Katharine for all the time that I should spend with her but was unable to. This dissertation is dedicated to them. I appreciate the United States Environmental Protection Agency for financial support during my Ph.D. Program. I also thank the Virginia Ag-Chemical and Soil Fertility Association, and the Virginia Tech Department of Entomology for additional financial support. v TABLE OF CONTENTS Section Pages Abstract..................................................................................................ii Acknowledgments.................................................................................iv Table of contents...................................................................................vi List of Tables .......................................................................................xii List of Figures.....................................................................................xiv Chapter 1. Introduction ........................................................................1 Chapter 2. Literature review................................................................5 2.1 Groundwater contamination.................................................................5 2.1.1. Pesticide groundwater contamination in the United States ........5 2.1.2. Chlorpyrifos groundwater contamination...................................6 2.1.3. Atrazine groundwater contamination .........................................6 2.2. Chlorpyrifos........................................................................................7 2.2.1. Chlorpyrifos volatilization from soil ..........................................7 2.2.2. Chlorpyrifos photolysis..............................................................7 2.2.2.1. Kinetics of photodegradation ......................................8 2.2.2.2. Photolysis pathway......................................................8 2.2.3. Chlorpyrifos hydrolysis..............................................................9 2.2.3.1. The pH affects of hydrolysis........................................9 2.2.3.2. Temperature effects...................................................10 2.2.3.3. Metallic ion catalyzed hydrolysis ..............................10 2.2.3.4. Hydrolytic pathway ...................................................11 2.2.4. Microbial degradation..............................................................11 2.2.5. Chlorpyrifos and TCP metabolic pathways in soil ...................15 2.3. Atrazine.............................................................................................17 2.3.1. Microbial degradation..............................................................17 2.3.1.1. Dechlorination of atrazine.........................................23 vi 2.3.1.2. N-dealkylation...........................................................24