Short-term effects of biosolid and municipal solid waste applications on heavy metals distribution in a degraded soil under a semi-arid environment

Digested biosolid (SS) and municipal solid waste (MSW) were surface-applied to a degraded carbonated soil, under semi-arid environment, at rates of 0 and 80 Mg/ha, to determine the changes in organic matter and in the distrib ution of heavy metals in the topsoil, 1 year after its application. Waste a pplication slightly increased the organic matter content and improved the c omposition of humic fractions in the treated soils, mainly in the MSW amend ed plots. A sequential extraction method (Tessier et al., 1979) was used to determine the distribution of Cd, Cr, Cu, Ni, Pb and Zn in both the waste and the amended soils. Waste application had little effect on the total con centration of Ni and Cr in the treated soils as a consequence of the low av ailability of these metals in the wastes. A considerable increase of Cd, Cu , Pb and Zn was observed as a consequence of the high content and/or high a vailability of these metals in the wastes. The more labile fraction (exchan geable fraction) of all metals studied increased slightly (< 1.5 mg/kg) whe n SS and MSW were added. However, a remarkable increase in the Fe/Mn oxide fraction of Cd, Cu and Pb and in the organic fraction of Zn were noted in t reated plots, this increase being higher in the MSW treated soils. (C) 2000 Elsevier Science B.V. All rights reserved.