EFFECT OF CRUSHED LIMESTONE BARRIERS ON CHROMIUM ATTENUATION IN SOILS

The influence of agricultural limestone as a low-cost landfill liner to retard the migration rate of Cr in municipal solid waste leachate through soils was studied. A limestone layer, 2 cm thick over a 10-cm depth of soil in a column, delayed the breakthrough concentration (C/C(o) = 1.0) of the Cr in the effluent manyfold over that without limestone. Crushed limestone was more effective in retaining the cation Cr(III) than the anion Cr(VI). Retention of Cr(III) in soils due to the presence of a limestone liner is much greater than that for other metals tested (Be, Cd, Fe, Ni, and Zn). There appears to be a combined influence on the retention of Cr between the limestone liner and soil not apparent when municipal leachate was passed through the limestone barrier and soil independently. Usefulness of limestone (ranging up to 16% at breakthrough concentration) depends primarily on the pH and volume of the solution passed through the limestone.