| Abstrakt: |
The adsorption of four volatile organic compounds (1,4-dichlorobenzene, 1,2-dichloroethane, 1,2,2-trichloroethane and 1,1,2,2,-tetrachloroethane) on three soil types from a Superfund site (Petroprocessors Inc) in Baton Rouge, LA was studied with the purpose of obtaining an overall correlation for inclusion in a groundwater transport model being developed for site remediation. The soil-water partition constant,Kd was determined using a standard ASTM procedure (E-1195-87). Using the data for different soil types (fraction organic carbon between 0.11% and 1.13%) and different mineral surface areas (7 to 45 m2/g), the organic carbon contribution (Koc)and the mineral matter contribution (Kmin) to the partition constant were determined. The soils obtained were either from the Pleistocene period or recent shallow deposits at the site. Both log Koc and log Kmin were linearly correlated to logKow, the octanol-water partition constant. This data provided the basis for obtaining a general correlation for Kd on different soil types at the site. The predicted values were in agreement with that for a composite soil from the same site. The desorption of compounds from the high clay soil after the 24 hour adsorptionperiod was observed to show a biphasic behavior, namely, an easily desorbed fraction and a desorption resistant fraction. The easily desorbed fraction was found to be satisfactorily predicted using the conventional Kd as obtained from the adsorption experiment. The slowly desorbing fraction had a time constant of several weeks. Theconcentration in the desorption resistant compartment was found to be dependant on the initial amount of contaminant available for adsorption. The aqueous phase concentration in equilibrium with the desorption resistant fraction was found to be approx. 8 microg/L for dichlorobenzene and approx. 12 microg/L for dichloroethane. [ABSTRACT FROM AUTHOR] |
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