FATE AND DISPOSITION OF TRICHLOROETHYLENE IN SURFACE SOILS (ADSORPTION, ISOTHERMS, COLUMN STUDIES)
Abstract
Trichloroethylene (TCE) is widely detected as a contaminant in groundwater due to discharges or spills. This study investigated the fate of TCE in two similar soils with differing organic carbon contents. TCE was applied to soil columns in one 5 or 10 ml quantity, then eluted over 132 consecutive days with 50 or 100 ml of water/day. The 1.4% organic carbon soil retarded elution of TCE more than did the 0.53% soil. Column effluent TCE reached 840-1,100 mg/l with the 0.53% organic carbon soil having higher TCE concentrations. For columns subjected to 10 ml TCE, effluent TCE remained constant at approximately 1,100 mg/l until 50-60% of applied TCE was eluted. Water application rate had no measurable effect on elution. Batch isotherms for both soils and two particle sizes (fine, < 0.150 mm; coarse, < 2 mm) paralleled the Freundlich theory. Adsorptive capacity increased with increased organic carbon content and decreased particle size. Based on normalized organic carbon content, adsorption was found to be dependent upon inorganic surface area. Equilibration time studies for 220-880 mg/l TCE showed adsorption to be complete within 20 hours. Biodegradation of TCE in the soils, based on effluent TCE and chlorides, was not enhanced by addition of ammonia to elution water. Warburg studies showed TCE was inhibitory to biological activity at concentrations of 55-1,100 mg/l in unacclimated soil. Acclimated soil of both types from 2.5 and 15 inch depths showed degradation of TCE at 55 mg/l but not 110 or 550 mg/l. Addition of ammonia enhanced mass of TCE respired but not respiration rate. No evidence of cis or trans-1,2-dichloroethylene was found in column effluents. In all, degradation (biological and abiotic) accounted for 0.3% or less of TCE. A mass balance indicated TCE retention in the soil directly correlated with soil organic carbon content. Elution and volatilization were major sinks for TCE. Volatilization accounted for 15.6-32.8% of TCE applied.
Degree
Ph.D.
Subject Area
Sanitation
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