Salinity as a factor controlling the distribution of heavy metal mobile fractions in soils of the Baraba forest-steppe

To assess the influence of salinity and chemical composition of readily soluble salts on the partitioning of heavy metals in soils of the Baraba forest-steppe, the vertical distribution of Co, Ni, Cu, Zn and Pb mobile fractions extracted by acetate-ammonium buffer and 1n HNO₃ and the total Co, Ni, Cu, Zn and Pb content were studied in associated Salic Mollic Gleyic Solonetz, Gleyic Chernozems, Calcic Oxygleyic Mollic Gleysols (Protosalic) with different salinity and Calcic Mollic Gleyic Solonchaks within two key sites. The amount of toxic salts varied from <0.1% (no salinization) in Gleyic Chernozems to 3% (very strong salinization) in So-lonchak topsoils. Some Gleyic Chernozems show the signs of alkalinization. Salinization of A and O horizons of Gleysols and Solonchaks by Na₂SO₄, NaCl and NaNO₃ increases the mobility of Co, Ni, Cu and Pb and supports their removal from topsoil horizons by radial and lateral flows. Mixed Na₂SO₄ and NaHCO₃ salinization of Solonetz and Gleysols leads to heavy metals accumulation on the alkaline-sorption barrier in Bn and Bk horizons. The distribution of Zn mobile fractions in the investigated soils is primarily determined by its biogenic accumulation due to the sorption and precipitation mechanisms.

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