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ENANTIOMER FRACTIONS OF CHLORDANE COMPOUNDS IN SEDIMENT SAMPLES FROM U.S. GEOLOGICAL SURVEY SITES IN LAKES, RIVERS AND RESERVOIRS
Citation:
Ulrich, E M., C S. Wong, S. A. Rounds, P. C. VanMetre, J. T. Wilson, A W. Garrison, AND W. T. Foreman. ENANTIOMER FRACTIONS OF CHLORDANE COMPOUNDS IN SEDIMENT SAMPLES FROM U.S. GEOLOGICAL SURVEY SITES IN LAKES, RIVERS AND RESERVOIRS. Presented at 23rd International Symposium on Halogenated Organic Pollutants and Persistent Organic Pollutants, Boston, MA, August 24-29, 2003.
Impact/Purpose:
Extend existing model technologies to accommodate the full range of transport, fate and food chain contamination pathways, and their biogeographical variants, present in agricultural landscapes and watersheds. Assemble the range of datasets needed to execute risk assessments with appropriate geographic specificity in support of pesticide safety evaluations. Develop software integration technologies, user interfaces, and reporting capabilities for direct application to the EPA risk assessment paradigm in a statistical and probabilistic decision framework.
Description:
The environmental behavior of the enantiomers of cis- and trans-chlordane has been the topic of much research since the first chiral separations on cyclodextrin gas chromatography (GC) columns. When chlordane is manufactured, it is always a racemic mixture (equal portion of two enantiomers). As the compounds move through the environment, physical processes, such as volatilization, photolysis, and OH radical reactions, are not likely to change the enantiomer signature. However, biological processes, including uptake, depuration, and metabolism often are mediated by chiral molecules, such as enzymes that cause changes in the enantiomer signature. Enantiomer behavior of chlordane has been reported in biota, soil, water, and air. Enantiomer signatures have been used to trace chlordane sources from soil in the Midwest, to air above the soil, and to air near the Great Lakes. Additionally, evidence of biological degradation has been shown through enantiomer signatures. To date there have been no reports of chlordane enantiomer trends in sediment. Previous studies of toxaphene congeners and PCB atropisomers in sediment samples have shown interesting enantioselective behavior. Because sediment cores are used as a historical record of contaminant deposition, it is important to ensure that the record is accurate and has not been changed by biological degradation. The goal of this research is to document the enantiomeric behavior of chlordane compounds in sediment samples. In addition to sediment cores, surficial and suspended sediment samples will help determine a likely source of contamination to sediment. Trends are analyzed with sediment type, location, deposition date, and concentration for various chlordane compounds.