Ecogeochemical features of soil and bottom sediments of the cluster area "Lake Itkul" in the State Natural Reserve "Khakassky"

The cluster plot "Lake Itkul" in the State Nature Reserve "Khakassky" with the total area of 55.5 km is located in the Republic of Khakassia (Shirinsky District). It includes a fresh water reservoir of unique purity and size with a water surface of over 23 km. The article outlines the special role of tectonic factors in the formation of the lake basin, including the Itkul flexure. Previously unpublished authors' materials on the content of pollutants in the soil cover of the cluster are given. They were obtained by statistical processing of data by means of the semiquantitative emission spectral analysis (26 elements) of thirty-three representative soil samples. P,Ti, Ba, Li detected near-Clarke concentrations compared with Clarke ones for soils. Elevated Clarke concentrations (K) are set for Sr, V, Co, Nb, Cu, Zn, Sc and Mo (K does not exceed three units). Eight elements Ba, Sr, V, Ni, Cu, Zn, Sn and Mo exhibit content often exceeding limit values within MAC from 1.4 (Zn) to 3 (V). At that, the total pollution index (Zc) in all these elements is 7.2 units, which characterizes the level of pollution of coastal lakes as permitted. The correlation analysis establishes the close (highly significant) positive correlation connections with a correlation coefficient k > 0, which are characteristic for Yb - Ni - Ga - Zn - Sc, Ga - Mn - Yb - Zn, V - Co and Mn - Co. The visualization of behavior of trace elements on the map diagrams shows that the spatial arrangement of ecogeochemical anomalies does not depend on the composition of soil cover, as well as on the geological, geomorphological and landscape features. Clearly defined anomalies in the soil cover on the area of 24 km are characteristic only for two elements - Cu and Mo. These anomalies are well correlated with lithogeochemical halos of these metals in unconsolidated sediments and bottom sediments identified earlier on the area of numerous small exhausted polymetallic deposits in the southern and south-eastern sides of the lake basin. The authors of the article concluded that the sources of pollutants in the soil cover of the Itkul cluster are ore-bearing rocks in the area of small-scale exhausted polymetallic deposits. Probably, the processes of soil formation were accompanied by the assimilation of some heavy metals taken from soil and bedrock and the eolian addition. Hence, the occurrence of anomalies is due to natural but not man-made causes. Limit values in bottom sediments from Lake Itkul exceed only for Sr (1.7 MAC) and V (2 MAC). The remaining elements are present in amounts below the MAC. Thus, the level of contamination of soil and bottom sediments of the Itkul cluster does not go beyond the minimum and low values of normalized parameters. It may be characterized as valid and the ecogeochemical state of the environment may be recognized as favorable.

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