LEAD AND ZINC LEACHING IN SOIL TREATED WITH IRON SMELTING RESIDUES

Abstract

In order to evaluate the dynamics of Zn and Pb in the soil, a greenhouse experiment was set up in pots filled with soil samples (Typic Hapludox) treated with increasing doses of iron smelting residues. It was set under a completely randomized design, in a 3×5 factorial scheme, with three replications, combining three iron smelting residues (mill scale, filter press mud, and phosphate mud), with five doses for each residue (0 t ha^-1, 1 t ha^-1, 2 t ha^-1, 4 t ha^-1, and 8 t ha^-1). Elephant grass was cultivated during 120 days, followed by common beans, for 75 days. In that period, contents of Zn and Pb were determined in the leachate. No Pb was found in the leachate, but Zn proved to be quite mobile in this soil. In soils treated with mill scale and filter press mud, no risk of groundwater contamination was observed, however, the 8 t ha^-1 phosphate mud rate increased Zn contents in the leachate above the maximum allowed by environmental regulations. This fact limits the use of such residue for agricultural purposes. The other two residues should be evaluated in field-scale tests aiming their agricultural use.

KEY-WORDS: Industrial residue; heavy metal; mill scale; filter press mud; phosphate mud.