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

Column and batch leaching experiments were performed to quantify leaching o f heavy metals (Pb, Cu, Cd and Zn) from scrap dirt representing different a ctivities at two iron scrap and metal recycling facilities. The scrap dirt is often found directly upon the bare unprotected soil at recycling facilit ies. In most cases the leaching of heavy metals was modest, within five tim es the leaching from reference soils, and the concentrations were usually w ithin a factor of 2 of drinking water criteria. The high pH of the scrap di rt samples seemed to control the leaching. However, scrap dirt from car bat tery salvage locations was different, showing lower pH and significant leac hing of lead (up to 8000 mu g Pb l(-1)), cadmium (up to 40 mu g Cd l(-1)), and zinc (up to 2000 mu g Zn l(-1)). The column and batch leaching experime nts gave comparable results at the order of magnitude level, and both appro aches 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 sol ution indicated that covering of the scrap dirt with an organic rich dressi ng for vegetation support would dramatically increase the leaching of heavy metals.