MINERALIZATION OF ALPHA-ISOMERS, GAMMA-ISOMERS, AND BETA-ISOMERS OF HEXACHLOROCYCLOHEXANE BY A SOIL BACTERIUM UNDER AEROBIC CONDITIONS

The degradation of uniformly C-14-labeled isomers (alpha, gamma, and b eta) of hexachlorocyclohexane (HCH), added separately to a mineral sal ts medium as a sale source of carbon, by a soil bacterium, Pseudomonas sp., under aerobic conditions was studied. During aerobic degradation , about 10-12% of the C-14 in alpha- and gamma-HCH was accounted for a s (CO2)-C-14 as compared to 5% from beta-HCH. Most of the C-14 in alph a- and gamma-HCH accumulated as water-soluble products, while formatio n of water-soluble products from beta-HCH was negligible. Almost all o f the C-14 in the three isomers of HCH was accounted for in different fractions (CO2, chloroform-diethyl ether, water phase) following bacte rial degradation under aerobic conditions. GC-MS analysis of beta-HCH residues in the chloroform-diethyl ether extract suggested the formati on of pentachlorocyclohexanol and tetrachlorocyclo-hexanediol as produ cts of aerobic metabolism of beta-HCH.