Adsorption-desorption of HCH and endosulfan on a soil.

Sorption - desorption of HCH (1,2,3,4,5,6 - Hexachlorocyclohexane) and Endosulfan (1,2,3,4,7,7 - Hexachlorobicyclo [2,2,1] -2 - heptene - 5,6 - bisoxy methylene sulfite) on soil was studied using the batch equilibration technique with initial concentrations for the two chemicals ranging from 0.03 to 340 microg ml(-1), which corresponds to a field application rate of 0.1 2.0 kg m(-2). Calculated slopes of the Freundlich sorption isotherms were near to 1. The Kf, Kd, and Koc values determined for endosulfan were at least an order of magnitude greater than that determined for HCH. Kf values were 209 and 8035 for HCH and Endosulfan respectively. Hysteresis was observed for desorption of both the chemicals. Studies showed that Endosulfan and HCH binding to soil was strong and desorption cannot be predicted from adsorption isotherms only.