Effects of Farming Techniques on Degradation of DDT in Historical Cotton Farms Open Access

Abstract

p,p’-Dichlorodiphenyltrichloroethane (DDT) was a popular pesticide in the mid 20^th century for commercial crop and livestock production. DDT remains in the environment for decades as either the original compound or its dechlorinated environmental metabolites p,p’-dichlorodiphenyldichloroethylene (DDE) and p,p’-dichlorodiphenyldichloroethane (DDD) which can bioaccumulate and translocate. Many studies have correlated these compounds (collectively referred to as DDX) with human health and environmental effects. DDX are xenobiotics that can disturb endocrine function resulting in infertility, premature births, delayed sexual development, and other hormone-mediated effects in wildlife. Several studies have reported that the rate of degradation of DDT into its metabolites is affected by various farming techniques like tillage, irrigation, and fertilizers. Georgia consistently has been one of the major farming states, specifically a large producer of cotton since the 19^th century, thus is likely to have high levels of DDX in the soil  of historical farms. Therefore, in this study, we aimed to determine if different farming techniques affect the decomposition of DDT in Walton County, Georgia, where farms historically grew cotton. In this study, several Walton County farms were sampled for soil, and churches were sampled as control sites. The extensive land history of the farms was recorded, and the soil levels of p,p’-DDT, p,p’-DDE, p,p’-DDD, o,p’-DDT, and o,p’-DDE were measured using gas chromatography-tandem mass spectrometry. The farm sites had detectable levels of p,p’-DDT, p,p’-DDE, and p,p’-DDD, while few sites had detectable levels of o,p’-DDT and o,p’-DDE. Control church sites had detectable levels of p,p’-DDT, p,p’-DDE, and p,p’-DDD, but lower levels of each analyte were detected compared to the farm sites. Tillage was found to speed up p,p’-DDE degradation, but there was no effect on p,p’-DDT degradation. Plowing caused an increased fraction of decomposition, but no metabolite was significantly increased. The largest difference in the degradation of DDT was based on the fertilizer type. Natural fertilizer sped up degradation of p,p’-DDT and p,p’-DDE; synthetic fertilizer increased p,p’-DDE degradation, but not p,p’-DDT degradation. Farmers could potentially use some of these farming practices to encourage further degradation of DDX to reduce the contamination in their soil.

Table of Contents

Introduction………………………………………………………………………………………………………………………...1

Materials and Methods …………………………………………………………………………………………………………. 12

Results………………………………………………………………………………………………………………………………..21

Discussion…………………………………………..…………………………………………..…………………………………..29

Conclusions…………………………………………..…………………………………………..…………………………………34

Supplemental Information…………………………………………..…………………………………………..…………….. .37

About this Honors Thesis

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School	Emory College
Department	Chemistry
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Analytical Environmental Studies
Keyword	DDT Farm Soil Pesticide Georgia
Committee Chair / Thesis Advisor	Saikawa, Eri, Emory University
Committee Members	Kindt, James, Emory University Weinschenk, Matthew, Emory University

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