Evaluation of contaminant transport parameters for hexavalent chromium migration through saturated soil media

摘要

Hexavalent chromium (Cr6+) is released in the lithospheric environment through leachate pollution in chrome tanning industries. Transportation of Cr6+ containing plume through soil needs to be assessed by estimation of some mechanistic parameters such as diffusion coefficient (D), distribution coefficient (K-d) and retardation factor (R). An investigation was undertaken with three soil samples, S1, S2 and B, to examine their potential use as liner material for controlling Cr6+ pollution in soil environment. Batch adsorption kinetic test was carried out to estimate the K-d and R values of soil samples S1 and S2. A numerical solution technique was adopted for prediction of such transport parameters in simulated field condition using the finite difference method (FDM). The efficacy of the present numerical solution technique (FDM) is compared with subsequent column experiment data with Soil-B along with the analytical solution. It was observed that the experimental value of "D = 3.04 x 10(-8) m(2)/s for Soil-B'' by using the applied technique closely fitted to that value evaluated by the analytical method (r(2) = 0.98). The values of 'K-d' for Soils S1 and S2 were found to be 0.008 and 0.021 mL/g, respectively, using batch adsorption. The values of 'R' of the soil samples S1 and S2 were obtained as 1.037 and 1.053, respectively. All the above results were obtained in correspondence to the initial hexavalent chromium concentration level of 7.5 mg/L in the simulated leachate sample.