Heavy Metal Speciation in Polluted Soil

Abstract

Heavy metal speciation in soil by means of sequential extraction provides more detailed information for assessment of metal mobility and bioavailability than the determination of total metal content in soils or extraction with 2 mol L^–1 HNO₃. The most often used reagents for extraction of different metal forms were used in the study. Two-step sequential extraction with 0.1 mol L^–1 Ca(NO₃)₂ (exchangeable metal forms) and 0.05 mol L^–1 Na₄P₂O₇ at pH 12 (organically bound forms) was applied to soil samples from heavily polluted alluvium of the Litavka river in the district of Příbram. Proportion of exchangable and organically bound metals in relation to metals extractable with 2 mol L^–1 HNO₃ followed the order Cd > Zn > Pb. This proportion was relatively lower at a high level of contamination. Zn manifested the highest mobility through the soil profile. Pb and Cd can be accumulated by the organic matter in topsoil.