PW11 Chiral Chemistry: Catching Pollutants Right-handed!
Exhibit Hall
8:00 AM - Wednesday, 12 November 2003
(PW187) Chiral polychlorinated biphenyl atropisomers in soils, sediments, and biota contaminated with Aroclor 1268.
Wong, Charles1, Ejsmont, Malgorzata1, Maruya, Keith2, 1 University of Alberta, Edmonton, AB, Canada2 Skidaway Institute of Oceanography, Savannah, GA, USA
ABSTRACT- Chiral polychlorinated biphenyls (PCBs) were measured in the soils, sediments, and aquatic food web at a southeastern coastal Georgia tidal marsh to determine potential biotransformation of heavily chlorinated congeners in this system. This Superfund site had been heavily contaminated with Aroclor 1268 from a former chlor-alkali plant. Previous achiral studies to characterize the composition and environmental fate of PCBs at this site have found inconclusive evidence for degradation of Aroclor 1268 congeners, which are thought to be recalcitrant to biotransformation due to their heavy chlorination (7 or more chlorines). Chiral analysis was thus used to quantify biodegradation potential, as only biological processes can change enantiomer distributions of chiral chemicals in the environment as a general rule. Nonracemic amounts of PCB 183 were found in soils, surficial sediments, and sediment cores throughout the site. This result suggests that stereoselective microbial biotransformation activities, most likely reductive dechlorination, have occurred in situ. Grass shrimp (Palaemonetes pugio) had enantiomer compositions similar to that found in sediment, consistent with uptake from dietary exposure to sediment detritus. Fish (mummichogs, striped mullet, and sea trout) also contained nonracemic PCB 183 compositions. These residues are like due to a combination of bioaccumulation from prey and in vivo elimination. Our results are consistent with previously reported measurements of nonracemic toxaphene in the food web of a nearby downstream site, and suggest that aquatic biota have the potential to biotransform even heavily chlorinated organochlorine contaminants.
Key words: bioaccumulation and biotransformation, chiral polychlorinated biphenyls, aquatic food webs, contaminated sediments