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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 Dioxin '03, Boston, MA, August 24-29, 2003.
Impact/Purpose:
The goal of this task is to contribute to a better understanding of human exposure to pesticides, especially for small children by developing methods to characterize sources and pathways in and around the residential environment. We will support the science behind FQPA and assist the Office of Pesticide Programs (OPP) in the development of guidelines for the assessment of residential exposure to pesticides. Specific research objectives include: (i) to evaluate and develop methods for measuring pesticides in air using passive/diffusive samplers. Assess and refine devices for the collection of surface transferable pesticide residues and to establish transfer efficiencies; (ii) to develop and apply analytical methods for new and emerging pesticides using both gas and liquid chromatographic methods in support of the National Exposure Research Laboratory's (NERL) Human Exposure Measurement Project; and, (iii) to conduct pilot studies investigating chiral chromatographic methods.
Description:
More than 500 important environmental contaminants are chiral (having structures that are nonsuperimposible mirror images). Although enantiomer pairs have identical physical-chemical properties, their toxicity, biodegradation, and environmental fate often are different. Cyclodextrin gas chromatography combined with mass spectrometry was used to determine the chiral characteristics of chlordane components in sediment. Enantiomer fractions [EF = area (+) enantiomer / sum of (+) and (-) areas] were used to determine if biological degradation had occurred in surficial and suspended-sediment samples, and if there was a trend with depth in sediment cores. Suspended sediment samples showed slight deviation from the racemic EF value of 0.50, suggesting that some biological degradation had occurred prior to sediment deposition in the water body. Surficial sediment samples also contained evidence of biodegradation [cis-chlordane (CC) = 0.492 - 0.620; trans-chlordane (TC) = 0.473 - 0.531; exo-heptachlor epoxide (HEPX) = 0.600 - 0.682]. At five core sites, EFs were close to racemic for TC and CC and in general, TC EFs were less than 0.5 and tend to increase slightly with depth, while the opposite was true for CC. There were no detectable amounts of two chlordane degradation products in sediment core samples. These results suggest that little biodegradation has occurred in the sediment core, and that historical concentration profiles should be unaltered by biological degradation processes.
This work has been funded by the US EPA and USGS. It has been subjected to EPA review and approved for presentation. Mention of trade names of commercial products does not constitute endorsement or recommendation for use.