The sorption of trichloroethylene (TCE) from vapor phase onto natural solids was investigated by batch sorption experiments. The effects of natural solid characteristics and moisture content on the sorption of TCE vapor were evaluated. As natural solids, six different US EPA soils and sediments were used. The moisture content of each natural solid was adjusted at four different values, including oven-dried condition. The linear sorption coefficients of TCE from the vapor phase (Kd’) were about one to four orders of magnitude greater than those from the aqueous phase. The Kd’ values for the oven-dried natural solids had poor correlation to the organic carbon content of natural solids. These results indicated that the sorption of TCE vapor was not controlled by the organic carbon referenced hydrophobic sorption. The Kd’ values for the oven-dried natural solids, however, correlate well with the cation exchange capacity (CEC) and swelling clay content of natural solids. The interaction of TCE molecules with the exchangeable cations on natural solid surface could be a dominant sorption mechanism. The Kd’ values decreased with increasing the moisture content of natural solids. The water on natural solid surface interferes the vapor-phase sorption of TCE onto the surface cations.

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