Sorption of selected organic pollutants in Danish soils

The sorption of benzoic acid, nitrobenzene, 4-nitrophenol, 2,4-dichlorophenoxyacetic acid (2,4-D), and naphthalene was determined for 10 Danish soils in laboratory studies. Measured equilibrium isotherms were of nonlinear Freundlich type for nearly all combinations of soil-test compounds. Adsorption was significantly correlated with the organic carbon content of the soils tested. No significant correlations with pH and cation-exchange capacity were observed. The adsorption of benzoic acid was found to be reversible and the sorption of naphthalene was reversible in 4 of 10 soils. A desorption-resistant fraction of adsorbed 2,4-D was estimated from interdependent adsorption and desorption isotherms.