Estimation of organic chemical sorption by soils

Sorption data for > 400 compounds were collected and analyzed. Sorption coefficients on an organic carbon basis (Koc) were found to be log-normally distributed. Correlations between log Koc and log aqueous solubility (S), log Kow (octanol-water partition coefficient) and molecular connectivity (MC) indices were calculated and their predictive ability determined with a set of test data not included in the original data set. It was found that the equations (log Koc vs.either log S or log Kow) for individual chemical groups were preferred over the general equation for all chemicals but that a group correction term (Fc) added to the total equation gave similar results. The use of MC indices alone were inadequate for predicting sorption values with the exception of a few homologous groups.