Congener and Enantioselective Analysis of Toxaphene in Sediment and Food Web of a Contaminated Estuarine Wetland

Abstract

Enantioselective gas chromatography with electron capture negative ion mass spectrometry (GC/ECNI-MS) was employed to investigate the fate of toxaphene residues in contaminated sediment (source) and biota (receptor) representing several levels of an aquatic food web. Samples were collected from an estuarine marsh that was impacted by discharge from a former toxaphene plant. Several penta- to nonachlorobornanes were identified and enantiomerically resolved on a chiral stationary phase. Additional peak confirmation was obtained after fine fractionation of extracts on silica. Previously identified congeners including B6-923 (Hx-Sed), B7-515 (P-32), B7-1001 (Hp-Sed), B8-806/9 (P-42), B8-1412, B8-1413 (P-26), B8-2229 (P-44), B9-1679 (P-50), and B9-2206 (P-63) were detected, as were several unknown penta- and heptachlorobornanes. The majority of prominent congeners were essentially racemic in marsh sediment (maximum deviation 15%). In contrast, several congeners as well as several unknown hepta-CTTs were enantioselectively depleted in lower food web organisms; the enantiomer ratios (ERs) for B6-923 and B7-1001 in small fish (Fundulus sp.) were ∼2 and 0.6, respectively. These significant alterations of the ERs prove that even low-trophic level biota is able to degrade toxaphene components to some degree. In higher level predators, the ERs for B7-1001 were closer to racemic. Irrespective of trophic level, little or no shift in the ERs for B8-1413 (P-26) and B9-1679 (P-50), two recalcitrant chlorobornanes in mammals, relative to sediment were observed. These results indicate that biochemical transformations within the scope of the estuarine food web studied likely act to alter the residue pattern and the ultimate fate of toxaphene.

Chirality as an Environmental Forensics Tool

“…Mummichogs naturally contaminated with toxaphene from a Georgia estuary eliminated one enantiomer of the congener B6-923 twice as fast as its antipode, with halflives of 6 and 13 days, respectively [224]. This experiment confirmed previous field observations [151]. However, natural attenuation was expected to be slow, given high contamination levels and slow elimination throughput.…”

“…A Georgia estuary heavily contaminated with toxaphene had racemic levels in sediment, but highly nonracemic compositions of B6-923 and B7-1001 in mummichogs (Fundulus sp. ), strongly suggesting that even low trophic level species could biotransform toxaphene to some extent [151]. In a similar vein, one of the only measurements of the cyclodiene pesticide bromocylen found racemic amounts in German rivers receiving wastewaters, but enrichments of the (þ)-enantiomer in bream (Abramis brama orientalis), again consistent with in vivo biotransformation [223].…”

“…Only one enantiomer of B6-923 was produced by laboratory reductive dechlorination of a heptachlorobornane in an anaerobic soil [150], suggesting that microbial consortia responsible in Hanson Lake were not those present in the laboratory study. In contrast, nine chlorobornane congeners, including B6-923 and B7-1001, were essentially racemic in estuary sediments heavily contaminated with toxaphene in coastal Georgia, USA [151]. The presence of likely parent congeners of B6-923 at this site suggested that reductive dechlorination, if it had taken place at all, was not dominant, possibly due to high toxaphene concentrations and/or lack of activity of appropriate microbial communities.…”

Wastewater Treatment and Reclamation: A Review of Pulp and Paper Industry Practices and Opportunities

“…The recalcitrance of an individual compound towards biological processes is related to the number and position of the halogen substituents (Naumann 1999). Additionally, enantioselectivity and chiral discrimination of optically active compounds can have an influence on the degree of their accumulation (Reich et al 1999;Vetter and Maruya 2000). Isomers, diastereomers, and enantiomers can have varying toxicity (Willett et al 1998;Carr et al 1999).…”

Polybrominated diphenyl ether congeners and toxaphene in selected marine standard reference materials

“…Toxaphene is persistent in the environment and responsible for fish consumption advisories in some locations [11]. Toxaphene is an analytically challenging mixture due to the often hundreds of congeners present in a sample, the presence of numerous stereoisomers, the limited availability of authentic standards of individual congeners, and the potential for interference from other compounds [12,13,14]. The objective of this study was to determine the concentrations of selected PBDE congeners, toxaphene congeners, and total toxaphene in several existing marine-matrix standard reference materials (SRMs).…”