RATE-LIMITED SORPTION OF HYDROPHOBIC ORGANIC-COMPOUNDS BY SOILS WITH WELL-CHARACTERIZED ORGANIC-MATTER

This study is focused on the rate-limited sorption of homologous serie s of polycyclic aromatic hydrocarbons, alkylated benzenes, chlorinated benzenes, and chlorinated alkenes by two soils, one in which the orga nic matter is dominated by humic acid and the other by fulvic acid. Th e solutes sorbed more strongly to the humic-dominated soil than the fu lvic-dominated soil. The first-order molecular connectivity index(X-1( v)), a molecular solute descriptor, provided slightly better correlati ons with equilibrium sorption coefficients than did the octanol-water partition coefficient (K-ow), an empirical solute descriptor. Thus, so rbate shape/structure may have a secondary influence on the overall ma gnitude of equilibrium sorption. However, sorbate shape/structure exhi bited a significant influence on sorption kinetics. Distinct differenc es were observed in the correlations of mass-transfer coefficients to X-1(v) for the two soils. The differences were attributed to both sorb ate shape/structure and the quantity (path length) and morphology of s oil organic matter.