FRACTIONATION AND OXIDATION OF CHROMIUM IN TANNERY WASTE AND SEWAGE SLUDGE-AMENDED SOILS

Clay, sand and peat soils were mixed with tannery waste so that the final concentrations of total chromium were between 1500 and 2000 mu g g(-1) and with sewage sludge where the final concentrations of total chromium ranged from 170 to 200 mu g g(-1). The experiment was carried out for 2 years under atmospheric conditions. Fractionation of chromium was studied in these soils employing a sequential extraction procedure and oxidation of chromium by measurement of chromium(VI) in the water-soluble fraction. The results of fractionation studies in tannery waste-amended soils indicated that 5 months after the start of the experiment up to 1.1% of total added chromium was oxidized in clay, 0.45% in sand, and only 0.03% in peat soil. The concentration of the water-soluble chromium and chromium(VI) decreased in further continuation of the experiment since chromium was redistributed to more sparingly soluble fractions of soils. The process of chromium oxidation was not observed in sewage sludge-amended soils.