摘要：Bioavailability of α - and β - isomers of a chlorinated insecticide hexachlorocyclohexane (HCH) in several field soils that were contaminated for different time periods was evaluated. Results revealed that the availability of α - HCH to the degradative microorganisms was 75 - 80% in all the soils, but considerable differences in the availability of β - HCH i n different soils were observed. Thus, 80 - 90% β - HCH was available to ' E.coli - LinB' cells from a freshly spiked soil, and ~70, 60 and 45% from soils that were contaminated for short - , medium - and long - term, respectively. Similarly, their amounts extracted by 50 mM hydroxypropyl - β - cyclodextrin also showed the same trend. It suggests that the bioavailability of β - HCH decreases progressively with an increase in the age of contamination, but of α - HCH is not affected under the same conditions. Reasons behind thi s differential availability are discussed. Results are important for correct risk - assessment of these residues in the contaminated soils.
