COMPLETE DISSOLUTION OF IMMISCIBLE-LIQUID PHASE TRICHLOROETHENE: CHARACTERIZING LOW-CONCENTRATION TAILING BEHAVIOR

Nonideal contaminant transport, specifically long-term elution tailing, has been attributed to several mechanisms. Characterization of nonideal transport behavior through the quantitative analysis of these multiple factors is necessary to evaluate contamination potential, conduct risk assessments, and for the planning and implementation of remediation systems. The objective of this study was to investigate the dissolution dynamics of immiscible-liquid phase trichloroethene in a naturally heterogeneous (poorly sorted) aquifer material, with a specific focus on characterizing the relative contributions of rate-limited dissolution and rate-limited sorption/desorption to low-concentration elution tailing. A comparison of trichloroethene elution behavior for systems with and without immiscible-liquid phase present suggests that the low-concentration elution tailing observed in the former experiments is associated with rate-limited sorption/desorption. The complete dissolution and elution of trichloroethene was successfully simulated using a mathematical model that combines independently determined descriptions of rate-limited dissolution and rate-limited sorption/desorption. Specifically, immiscible-liquid dissolution of trichloroethene was described using a first-order mass transfer approach with a temporally variable dissolution rate coefficient, and rate-limited sorption/desorption was described using a continuous-distribution approach. The results of this study clearly indicate that multiple processes contributed to trichloroethene elution behavior when immiscible-liquid phase was present, and that a multi-process model was required to accurately predict the measured data.