Simultaneous Measurement of Specific Discharge and Cr(VI) Mass Flux in Porous Media Using Permeable Adsorbent Device

摘要

The method for simultaneous measurement of local groundwater specific discharge (q) and Cr(VI) mass flux (J(exp Cr)) using a permeable adsorbent device is proposed. The proposed method allows for determination of both q and J(exp Cr) as two-dimensional vectors, with each vector composed of an angular (q(Theta), J(Theta)(exp Cr)) and a radial (q(sub r), J(sub r)(exp Cr)) component. The device consists of a cylindrical container whose outer shell is constructed of highly permeable mesh material with impermeable end caps. The interior of the device is divided into a center well and three outer sectors, each packed with a granular anion exchange resin having high adsorption capacity for the Cr(VI) oxyanions CrO(sub 4)(exp 2-) and HCrO(sub 4)-. The adsorbent in the center well of the device is loaded with berizoate as resident tracer. Experiments were conducted in which these devices were placed in porous packed bed columns through which was passed a measured quantity of simulated groundwater containing Cr(VI). The resin was then removed from the four sectors separately and extracted to determine the masses of Cr(VI) and resident tracer bound in each. A linear solute transport model was used to relate the observed rate of resident tracer displacement to q(Theta) and q(sub r), and a simple mass balance equation was used to calculate J(sub r)Cr. Experimental results showed q(Theta) was measured to an accuracy of plus or minus 1 degrees. Accuracy of the radial specific discharge vector component depended on the degree of displacement of the resident tracer. J(sub r)(exp Cr) mass flux vector radial component was measured to an accuracy of plus or minus 17%. These results demonstrate that the proposed method represents a promising technique for determination of specific discharge and contaminant mass flux in contaminated aquifers.