Features of technogenic heavy metals accumulation in soils of cities in Middle and Lower Volga region

Priority pollutants in the cities of the Middle and Lower Volga region are the elements of the group of heavy metals. They are found in the atmosphere as a result of increased motor transport units, reconstruction of production facilities, expansion of the city transport infrastructure as a whole, and cluttering of the territory. Soils are one of the most important accumulators of technogenic heavy metals from the environment in the context of urbanization. The content of heavy metals in soils reflects the potential danger of technogenic pollution of the soil and the environment as a whole, which causes irreversible changes in the structure and ecological properties of urban soils. Environmental analysis of the level of ecological danger of urban soils pollution in the Middle and Lower Volga region with heavy metals was carried out in the calculated values of the total chemical contamination. The most dangerous pollutants of urban soils of the Middle and Lower Volga region are lead, copper and zinc. The maximum concentrations of the pollutants were identified in cities with a developed industrial and transport infrastructure: Saratov, Volzhsky (Volgograd Region), Dimitrovgrad (Ulyanovsk region). The lowest concentrations of lead, copper and zinc were identified in Balashov (Saratov Region), Serdobsk and Kuznetsk (Penza Region). The permissible level of pollution of anthropogenically modified soil is typical of the cities Serdobsk, Balashov, Inza, Kamyshin. In the city of Kuznetsk soils are characterized by a moderately dangerous level of pollution. In the largest cities of the study area - Saratov, Volzhsky, Dimitrovgrad - technogenic soils are significantly contaminated and are characterized by a dangerous level of chemical pollution. As a result of soil monitoring in the area of research the overall pattern of accumulation of technogenic heavy metals was made: data on elements are collected not for the entire depth of the soil profile, but only for the upper, organogenous horizons. The main factor of their accumulation in the soils is clay minerals and organic matter. This fact is typical of all the cities in the study area. Further there is a gradual decrease of the content of heavy metals in the deeper layers of the urban soils. To a greater extent the soil cover of the studied functional zones (industrial, residential, recreational) is exposed to technogenic pollution of heavy metals in the cities with developed industry and a powerful transport load - in Saratov, Volzhsky, Dimitrovgrad, Kuznetsk; to a lesser extent - in Kamyshin, Serdobsk, Balashov, Inza.

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