Fractional and Group Composition of Cr, Ni, and Mn Compounds in the Main Types of Soils in Background and Contaminated Areas in the Forest-Steppe Zone in Novosibirsk Oblast

In total 23 plots on background and polluted areas exposed to the Novosibirsk Tin Works, thermal power plants, and highways in the forest-steppe zone in the Novosibirsk oblast were studied. The soils comprise alluvial soil, soddy-podzolic soil (Rendzic Leptosol), gray forest soil (Luvic Greyzemic Phaeozem), leached chernozem (Luvic Chernozem), urbanozem, and agrozem. The total Cr and Mn contents in the studied soils do not exceed tentatively permissible limit values for the metals. The Ni concentration in sandy and sandy loamy soils of the Novosibirsk agglomeration is higher than the threshold limit. The mobility of heavy metals is increased in the soils exposed to technogenic emissions. We use our own combined fractionation scheme to trace in detail the transformation of Ni, Mn, and Cr compounds in the soils exposed to anthropogenic impact. The group of loosely bound Mn compounds, characterizing the bioavailability of the metal, accounts for up to 38% of the sum of fractions, mainly because of active Mn interaction with Fe–Mn oxides and carbonates. As for the group of firmly bound Cr compounds, they account for up to 98% of the sum of fractions, with most of the metal concentrated in the residual fraction (up to 89%). In the case of Ni, the Fe–Mn oxides and organic matter play a major role in its strong retention (up to 20 and 12%, respectively). The effects of soil properties on the accumulation and degree of fixation of heavy metals are assessed using soil buffering capacity index. Nonsilicate Fe compounds are shown to be active players in the retention of studied metals in alluvial sandy loamy and sandy soils.