Chromatographic models for the sorption of neutral organic compounds by soil from water and air

Abstract

The solvation parameter model is used to construct models for the estimation of the soil–water and soil–air distribution constants and to characterize the contribution of fundamental intermolecular interactions to the underlying sorption processes. Wet soil is shown to be quite cohesive and polar but relatively non-selective for dipole-type, lone-pair electron and hydrogen-bond interactions. Using a comparison of system constant ratios chromatographic systems employing reversed-phase liquid chromatography on polar bonded phases are shown to provide suitable models for estimating soil–water distribution constants. No suitable gas chromatographic models were found for the soil–air distribution constant but the requirements for such a system are indicated. Models are also provided for adsorption at the air–water interface. Estimation methods based on either the solvation parameter model or chromatographic model reproduce experimental distribution constants for a wide variety of compounds with a similar error (0.2–0.3 log units) to that expected in the experimental data.