Fractional and group composition of Cr, Ni and Mn compounds in the main types of soils in background and contaminated areas of the forest-steppe zone of the Novosibirsk region

The studies were conducted at 23 sites laid out on the soils of background and contaminated territories exposed to the Novosibirsk Stannum Plant, thermal power plant, highways of the forest-steppe zone of the Novosibirsk region. The soils are represented by alluvial, Rendzic Leptosols, Luvic Greyzemic Phaeozems, Luvic Chernozems, urbanozems, and agrozems. The total content of Cr and Mn in the studied soils does not exceed the approximate permissible concentration of metals. In sandy and sandy loam soils of the Novosibirsk agglomeration, the approximate permissible concentration for Ni was found to be exceeded. An increase in the mobility of heavy metals in soils of contaminated zones was revealed. Analysis of the fractional-group composition of Ni, Mn, and Cr compounds in soils using a the author’s combined fractionation scheme made it possible to trace in detail the transformation of heavy metal compounds in soils subject to anthropogenic influence. The group of loosely bound Mn compounds characterizing the bioavailability of the metal accounts for up to 38% of the sum of fractions, mainly due to active interaction it with Fe–Mn oxides and carbonates. The group of tightly bound Cr compounds accounts for up to 98% of the sum of fractions, with most of the metal concentrated in the residual fraction (up to 89% of the group). In the case of Ni, Fe–Mn oxides (up to 20%) and organic matter (up to 12%) play a major role in strong retention. Using the soil buffering capacity index with respect to heavy metals an assessment of the influence of soil properties on the accumulation and strength of element fixation is given. Active participation of non-silicate Fe compounds in alluvial sandy loam and sandy soils in the retention of the metals under consideration is established.