Methodological approaches to the assessment of heavy metal contamination in urban ecosystems soils

The paper presents the assessment of heavy metal pollution of Abakan soils, the main source of which is motor transport. The pollution assessment of the upper horizons soils located near four main highways of the city was conducted under established standards. The maximum concentration of elements was recorded in the area with very high traffic, which confirms the importance of the role of motor transport as the main source of pollutants. When calculating the total pollution index (Z_c) all highways were in a «dangerous» category. A similar indicator calculated on the basis of the data content in the soil-forming rock, allowed us to determine the degree of pollution as «moderately hazardous». Analysis of heavy metals content in soil profiles has allowed to establish in the upper soil horizons, a significant excess of gross and mobile forms of all elements at sites with very high and high degree of traffic load, which indicates intense аerogenic intake of pollutants. Determined the proportion of elements of anthropogenic origin and the fact of the uneven distribution of heavy metals in the soil profile and their concentration in different geochemical barriers. When determining causal relationships between heavy metal content and separate soil characteristics we have found a direct dependence on the following parameters: pH, humus, cation exchange capacity, carbon dioxide, carbonates, particle size distribution, and in some cases we can talk about complex influence of soil properties on the concentration of elements. Assessment of heavy metal contamination in urban ecosystems soils, using the data content of elements in soil-forming rock with the use of the profile approach is the most objective.