Transport of Heavy Metals during Infiltration of Simulated Highway Runoff through Large-Scale Soil Columns

Abstract

An evaluation was conducted of the performance of three Washington State soils in attenuating trace heavy metals (Cd, Cu, Pb, and Zn) in contaminated water. Although previous investigations of this kind have used relatively small-scale soil columns as indicators of actual performance, large-scale soil columns (0.3 m in diameter and 1 m deep) were tested under loading conditions similar to actual field infiltration basins. The soil columns were loaded periodically to produce quasi-field conditions, with the corresponding metal transport being observed as a function of depth. The data indicate that metals speciation and background metals present in the soil are important factors to consider, because they can affect expected metals removal rates of soils. The hydraulics of the system played a secondary role to the geochemistry. Results suggest that infiltration can be a viable alternative in disposing of runoff at low metals concentrations, if the soil-water system's assimilative capacity is not taken for granted.