ИСТИНА

It is known that street dust is an integral component of the urban ecosystem. It can have a significant impact on environmental components, changing the global and surface air urban climate and being a source of soil and atmosphere contamination. Near highways, dust transfer is intensified, that’s why there is a possibility of soil horizons formation from solid airborne deposits. Properties of solid atmospheric precipitation and of two yang soils, formed from this precipitation, were investigated. Soils were formed within 10-20 years with high and average dust load (about 330 g/m2 and 30 g/m2 per year, respectively). Dust goes into the soil in an aggregated state. It contains oil products (up to 2-3 g/kg), heavy metals, carbonates (up to 10 %), and up to 7 % of organic carbon. Particles of 0.01-0.05 mm and < 0.001 mm predominate. Spores of microorganisms and organic debris indicate that solid atmospheric precipitation is an intermediary for the distribution of living organisms in urban ecosystems. The studied soils were classified as Urby-Leptic Technosols underlain road surfaces. In thin sections, soil formation processes are related not only to the transformation of organic residues but of mineral base: the stagnation of moisture on asphalt leads to the variable redox environment, defining an active manganese and iron compounds formation, and saturation moisture promotes recrystallization of carbonates coming with solid precipitation. Chemical properties of the considered soils are similar to those of a typical Moscow urban soils and dust. The dust composition studies give an idea about the nature of the material constantly coming to the surface of urban soils. This material causes hard pollution by oil compounds and heavy metals, high carbonate rate, high organic carbon content, loess fraction predominance in fine-earth particles composition. While studying soils formed on atmospheric dust sediments underlain with impervious road surfaces, it becomes clear that airborne particles are the base for the formation of some main diagnostic properties of urban soils because the deposited dust is being mixed quickly with the material of urban soils due to the activity of living organisms in usual conditions.