Leachability of heavy metals from scrap dirt sampled at two scrap iron and metal recycling facilities

Abstract

Column and batch leaching experiments were performed to quantify leaching of heavy metals (Pb, Cu, Cd and Zn) from scrap dirt representing different activities at two iron scrap and metal recycling facilities. The scrap dirt is often found directly upon the bare unprotected soil at recycling facilities. In most cases the leaching of heavy metals was modest, within five times the leaching from reference soils, and the concentrations were usually within a factor of 2 of drinking water criteria. The high pH of the scrap dirt samples seemed to control the leaching. However, scrap dirt from car battery salvage locations was different, showing lower pH and significant leaching of lead (up to 8000 μg Pb 1-1), cadmium (up to 40 μg Cd 1-1), and zinc (up to 2000 μg Zn 1-1). The column and batch leaching experiments gave comparable results at the order of magnitude level, and both approaches are, at that level, useful for evaluation of leaching potentials from scrap dirt. The experiments showed that scrap dirt at recycling facilities constitutes only a modest leaching problem, but a long-term soil pollution problem from a land-use perspective. Leaching experiments with compost solution indicated that covering of the scrap dirt with an organic rich dressing for vegetation support would dramatically increase the leaching of heavy metals.