Remediation of Solvent-Contaminated Soils by Aeration
Kempton, Houston | Davis, Andy | Olsen, Roger
A bench-scale box test was performed to evaluate the feasibility of rototilling to remediate excavated soils contaminated with tetrachloroethylene (PCE), trichloroethylene (TCE), and 1,1,1-trichlorocthane (1,1,1-TCA). Two clay-rich soils (A and B) containing 0.15% organic C and different concentrations of the target analytes were placed in 15-cm thick layers under a 10 km h⁻¹ wind, tilled daily, and samples collected and analyzed periodically. Soil A (25 000 µg kg⁻¹ PCE) lost 80% after 24 h and 97% after 407 h. Soil B (8881 µg kg⁻¹ PCE) lost 29% after 24 h and 92% after 407 h. Initial TCE and 1,1,1-TCA concentrations ranged from 793 to 1570 µg kg⁻¹. Relative volatilization loss rates were similar to that of PCE. The average volatilization half-lives of the solvents were 1.2 d for PCE, 0.58 d for TCE, and 0.64 d for 1,1,1-TCA. Removal of the analytes slowed considerably after 200 h, with a small (up to 10%) amount of each analyte retained in refractory sites. Residual solvent concentrations in soils A and B after 407 h were 835 and 719 µg kg⁻¹ PCE, 38 and 95 µg kg⁻¹ TCE, and 21 and 31 µg kg⁻¹ 1,1,1-TCA. Simulations of volatilization using the pesticide root zone model (PRZM) accurately predicted the loss of PCE, TCE, and 1,1,1-TCA over the first 24 h when most of the solvent volatilized, but the model over predicted contaminat losses at longer durations when remnant soil concentrations were less than six times the concentration bound to refractory sites.
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