Distribution of heavy metals in bottom sediments of Lake Balkhash depending on natural and anthropogenic factors

Results of the investigation of the bottom sediments of Lake Balkhash at the modern stage are represented in the article. The distribution of heavy metals in bottom sediments depending on natural and anthropogenic factors is considered. A comparative analysis of toxicant content was made in bottom sediments and in Balkhash soil. It was detected that copper is accumulated more in bottom sediments. The content of copper and lead exceeds the common level almost in every region of Western Balkhash and in hydrochemical region VII. There is accumulation of zinc in region IV of the lake. According to the research, a dependence was noted between accumulation of heavy metals and weight of bottom sediments structure and amount of organic substance. There is accumulation of heavy metals largely in the micro-fine classes: silts and clays. A positive correlation between the concentration of heavy metals and organic substance was found. The calculation of accumulation coefficient showed that bottom sediments of hydrochemical region IV were more subjected to metamorphism. The areas of local pollution of bottom sediments with heavy metals were defined. They include the Bight of Bertys and the Gulf of Torangalyk, where toxicants with industrial wastes arrived for many years. It resulted in the metamorphism of the structure of bottom sediments. Exceeding common meaning for copper and lead is 30 in bottom sediments of Bight of Bertys. The content of zinc is 10 and cadmium five times higher in the considered region. Similar meanings of the given indexes are lower in the Gulf of Torangalyk, they are in the interval 2-8. Direct influence of technogenic pollution sources on the bottom sediments was shown. The total area of pollution by cooper is about 3453 km , lead is about 2960 km , zinc - 2513 km , cadmium - 1447 km . In the lake area, concentrations of heavy metals are characteristic for estuarine sediment sections of the rivers. As compared with the 1990s concentrations of metals are 3-4 times lower in the bottom sediments of regions III and IV. There are no significant changes in the quality and quantity of sediment structure, though there is a trend of a decrease in toxicants. Due to the high buffering capacity of the lake, the favorable level of security at the time and due to the weakening of the anthropogenic load of the existing industrial complex, the contamination of bottom sediments did not significantly impact the toxicological state of the aquatic environment.

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