Chromatographic separation of the enantiomers of marine pollutants. Part 6: Comparison of the enantioselective degradation of α-hexachlorocyclohexane in marine biota and water

Chirality as an Environmental Forensics Tool

“…The first report of enantiomerspecific POP distributions in the environment [110] found a slight but significant enrichment of (À)-a-HCH (mean EF ¼ 0.47) in waters of the North Sea, and suggested that the cause was microbial degradation in the water column. Similar EFs for a-HCH were subsequently observed there [111]. Racemic a-HCH was found in rain and air in nearby Norway [112], suggesting that wet deposition was not the source of enantioenriched a-HCH to the North Sea.…”

“…However, without accurate knowledge of the underlying food web, it is not clear if the nonracemic residues were indeed due to in vivo biotransformation or to uptake from prey, or some combination of the two. For some species -flounder (Platichthys flesus) from the North Sea [111], herring from the Baltic Sea [219], and Arctic cod in the Northwater Polynya [137] -enrichments of (À)-a-HCH (EF range of 0.44 to 0.47) were similar to those found in surrounding waters. Thus, no evidence of enantioselective bioprocessing was evident if planktonic prey of such species are assumed also to have similar enantiomer compositions, which was the case as measured in the Northwater Polynya [137] but not the other two studies [111,219].…”

“…This observation suggests the possibility of in vivo enantioselective processing of a-HCH by this species [137]. Likewise, other studies have found nonracemic amounts of a-HCH [111], PCBs [66,196], a-HBCDD [193], and the musks HHCB, AHTN, ATII, and AHDI [197] in several species of bivalves: blue mussel, Mytilus edulis; the freshwater clam, Corbicula sp. ; the clams Mya truncate and Serripes groenlandica; and zebra mussel, Dreissena polymorpha, respectively.…”

“…Eider ducks (Somateria mollissima) from the Baltic Sea were enriched in (þ)-a-HCH with EFs ranging from 0.62 in kidney to 0.13 in muscle [238]. These values were considerably more nonracemic than in their blue mussel prey (Mytilus edulis), which were enriched in the (À)-enantiomer (EF ¼ 0.44 to 0.48) [111], or the waters of the North Sea with EFs from 0.46 to 0.53 [238], suggesting preferential in vivo metabolism of (À)-a-HCH by eider ducks. Brain tissue was highly enriched in (þ)-a-HCH [111,239], strongly suggesting enantioselective blood-brain transfer of this chemical.…”

“…These values were considerably more nonracemic than in their blue mussel prey (Mytilus edulis), which were enriched in the (À)-enantiomer (EF ¼ 0.44 to 0.48) [111], or the waters of the North Sea with EFs from 0.46 to 0.53 [238], suggesting preferential in vivo metabolism of (À)-a-HCH by eider ducks. Brain tissue was highly enriched in (þ)-a-HCH [111,239], strongly suggesting enantioselective blood-brain transfer of this chemical. In the Northwater Polynya, low biomagnification factors in seabirds, coupled with racemic a-HCH in Arctic cod prey and nonracemic residues in bird tissues (EF range of 0.65 to 0.97), implied in vivo biotransformation by the seabirds [137].…”