QSAR modelling of soil sorption. Improvements and systematics of log KOC vs. log KOW correlations

A systematic study was performed to evaluate the quality and reliability of the quantitative relationships between the soil sorption coefficients and the n-octanol/water partition coefficients (log KOC vs. log KOW). A system of QSAR models has been derived which is based on a reliable set of experimental log KOW data (LOGPSTAR data) or reliable estimates calculated with the latest version of the ClogP algorithm. Particular emphasis has been made to clearly define the boundaries for application of developed models as well as the quality of estimates. Thus, for each developed model the application domain is clearly defined through the chemical (structural) domain, substituents domain, and X-variable domain. Finally, the QSAR model with the first-order molecular connectivity indices has been incorporated in the derived system of QSAR models since the soil sorption estimates of the predominantly hydrophobic chemicals based on the log KOW data have large uncertainties, particularly in the log KOW data range from 4 to 7.5.