Predicting dissolved organic carbon partition and distribution coefficients of neutral and ionizable organic chemicals

Abstract Estimating K DOC (dissolved organic carbon/water partition coefficient) and D DOC (dissolved organic carbon/water distribution coefficient) of neutral and ionizable organic chemicals is a crucial task for assessing mobility, modelling transport, environmental fate of a variety of chemicals and for evaluating their bioavailability in terrestrial and aquatic environments. A critical literature search of reliability-selected K DOC and D DOC values was performed to setup novel predictive relationships for K DOC and D DOC of neutral and ionizable organic chemicals. This goal was pursued by using: 1) LSER (linear solvation energy relationship) models to predict K DOC for neutral chemicals using Abraham solute parameters calculated for different DOC sources (all DOC sources together, soil porewater, surface water, wastewater and Aldrich humic acid (HA)); 2) linear regressions for predicting D DOC of organic acids from the octanol/water partition coefficient (Log K OW or Log P) and the dissociation constant (pKa), accounting separately for the contribution of the neutral and ionic fraction. The proposed models predicted Log K DOC and D DOC values within a root mean square deviation (RMSD) generally smaller than 0.3 log units.