DESORPTION-KINETICS OF SELECTED VOLATILE ORGANIC-COMPOUNDS FROM FIELD CONTAMINATED SOILS

Batch experiments conducted with five, low organic carbon content (0.04-1.12%), field contaminated soils (three silty-clay and two sandy soils) for the simultaneous desorption of trichloroethylene, tetrachloroethylene, toluene, and xylene showed that a substantial portion (48-94%) of the sorbed contaminant mass resisted desorption in deionized water-soil mixtures after 7 days of contact time. The desorption pattern was biphasic, a slow desorption following an initial fast phase. The rate and extent of desorption were independent of soil and sorbate properties such as organic carbon content, cation-exchange capacity, specific surface area, and water solubility. Correlations could not be established between the soil partition coefficient and soil properties. A silty-clay soil amended with trichloroethylene showed increased resistance to desorption with increasing residence time. A linear relationship was found between the soil partition coefficient and the desorption-resistant fraction of trichloroethylene.