Impact of geochemical barriers on the accumulation of heavy metals in urban soils

Based on multidimensional statistical models that connect the levels of contents of heavy metals and metalloids in the soils of the Eastern Administrative Okrug of Moscow with landscape and anthropogenic factors, a comparative estimation of the capacity of the complex geochemical barriers in the surface layers of urban and background soils is carried out. The share of heavy metals fixed in the urban soils due to the technogenous transformation of their physical and chemical properties, which amounted to 40–50% of the total content for Bi, Pb, Cd, Sb, As, and up to 26–30% for Zn and Cu, is calculated. The growth in the content of Bi, Sb, As, Cu, Pb, and Zn in urban soils is caused by an increase in the quantity of iron and manganese oxides. The increase in the content of Sb, As, and Pb is related to organic matter; and the rise in Bi, Cd, and Cu has resulted from the increasing amounts of the silt and clay particles in the soils, which indicates the leading role of sorption geochemical barriers. Cu, Zn, and Cd also accumulate on alkaline barriers.