LEACHING OF HEXACHLOROCYCLOHEXANE ISOMERS IN A FLOODED FIELD UNPLANTED OR PLANTED TO RICE

Leaching of alpha-, beta-, gamma- and delta-isomers of hexachlorocyclo hexane (HCH) in a commercial formulation, sprayed to a flooded field ( unplanted or planted to rice) at 1.0 kg a.i. ha(-1) on gamma-isomer ba sis, was studied with the help of field-installed porous moisture extr action cups. Residues of HCH-isomers in the surface field water and le achates (at 15, 30 and 60 cm) were higher in planted field than in unp lanted field, probably due to less volatilization of HCH-isomers under the crop cover. HCH-isomers, with the exception of beta-isomer, migra ted to 30 cm depth; beta-isomer did not move beyond 15 cm depth possib ly due to lower amount of this isomer available for leaching while alp ha-HCH was detected even at 60 cm depth. gamma-Tetrachlorocyclohexene, a predicted metabolite of gamma-HCH in anaerobic environments, was de tected in the the leachate even at 60 cm depth.