GEOECOLOGY OF THERMOKARST LAKES OF WESTERN SIBERIA IN THE ZONE OF INFLUENCE OF AN ARCTIC TOWN (A CASE STUDY OF THE TOWN OF NADYM)

The paper provides geoecological assessment of natural and urban thermokarst lakes for the town of Nadym, typical of the West Siberian Arctic. Although there is no developed industry in the town, we have found that there occurs an anthropogenic transformation of the geochemical composition of the surface waters of urban thermokarst lakes in comparison with background ones, which is manifested in an increase in the alkalinity of water and in chronic contamination with petroleum products. The reasons for these changes are littering of coastal zones with construction debris and historical pollution with cement dust from the house-building plant. Surface waters and bottom sediments of urban lakes contain significant concentrations of petroleum products, which for a long time have been carried into lakes by surface runoff from the territory of garage cooperatives of the industrial zone. It is shown that geochemical analysis of urban lakes should consider not only neutral or increasing effects of natural factors but also local conditions and the historical aspect of anthropogenic impact.