Temperature and Congener Structure Affect the Enantioselectivity of Toxaphene Elimination by Fish (original) (raw)

2005, Environmental Science & Technology

Recent advances in enantioselective separation techniques have enabled scientists to investigate environmental fate processes of chiral pollutants. In this study, congenerand enantiomer-specific toxaphene residues were monitored in captive, naturally contaminated fish (Fundulus heteroclitus) to characterize the effect of temperature and compound structure on the enantioselectivity of the elimination process. A previous study performed under warm water conditions (T mean ) 25°C) demonstrated relatively rapid (t 1/2 ≈ 7-14 d) and enantioselective elimination of the reductive dechlorination metabolites 2-exo,3-endo,6-exo,8,9,-10-hexachlorobornane (B6-923 or Hx-Sed) and 2-endo,3exo,5-endo,6-exo,8,9,10-heptachlorobornane (B7-1001 or Hp-Sed). As expected, repetition of this experiment at cooler water temperatures (T mean ) 15°C) resulted in a decrease in overall (i.e., both enantiomers) first-order elimination rate constants. Enantiomer fractions or ratios (EFs/ ERs) during elimination, however, varied by congener, ranging from racemic for very rapidly eliminated Cl 5 homologues to increasingly nonracemic for selected Cl 6 -Cl 8 homologues (including B6-923, several unknown Cl 7 compounds, B8-1414, and B8-1945). As a result, we propose a classification to describe the environmental persistence of chiral toxaphene pollutants based on congenerspecific elimination kinetics and susceptibility to biotransformation as measured by EFs/ERs.