Rapid degradation of γ-HCH in upland soil after multiple applications

Since 1973, the authors have carried out a long-term upland field experiment by applying γ-HCH (γ-BHC, lindane) every year in the same field in order to examine how the fate of γ-HCH was afrected in the long run. The disappearance-rate of γ-HCH increased with the increasing period of application. After the third and fourth applications of γ-HCH, more than 80% of the applied γ-HCH was lost within 1 month. The rapid loss of γ-HCH in the field was considered to be principally due to the degradation by microorganisms accumulated in the field for the long-term experiment. This asssumption was supported by several laboratory experiments: which indicated that the γ-HCH-decomposing microorganisms could survive and decompose γ-HCH in other soils to which γ-HCH had never been applied and that the active γ-HCH-decomposing microorganisms were aerobic or facultative anaerobic bacteria.