Fractionation of chromium in soils treated with aqueous solutions of Cr(VI) and Cr(III)

Fractionation of chromium was studied in various soils (clay, peat, sand and luvichromic cambisols) incubated thirty days with an aqueous solution of Cr(VI) or Cr(III) employing a sequential extraction procedure. The total concentration of chromium in easily and sparingly soluble fractions of soil (organic, Fe and Mn oxides and hydroxides, carbonate, sulfide and silicate mineral) was investigated and compared with the same soils of the natural origin. The concentration of Cr(VI) in the easily exchangeable fraction of soil was also determined. The results of fractionation studies in soils treated with an aqueous solution of Cr(VI) thirty days after application indicated that chromium remained mostly as exchangeable chromium in luvi-chromic cambisols, clay and sand soil. The exchangeable chromium was below the detection limit in peat soil. Chromium was mostly found in the organic fraction. In all four soils, the concentration of chromium in Fe and Mn oxides and hydroxides fraction was also higher in comparison to other sparingly soluble fractions of soil. On the other hand, thirty days after the application of an aqueous solution of Cr(III), chromium was found mostly in organic fraction, bound to Fe and Mn oxides and hydroxides and in carbonate fraction. The concentration of exchangeable chromium was also very high in clay and luvi-chromic cambisols with respect to peat and sand soil.