Radioecological state of lakes in the southern Ural impacted by radioactivity release of the 1957 radiation accident

This paper is concerned with the distribution of 90Sr and 137Cs in lake ecosystems in the southern Urals which were affected by the 1957 radiation accident. In 1992, the levels of 90Sr in the most highly contaminated lakes, which were removed from economic usages, were as follows: 17–120 Bq l−1 in water, 70–110kBq kg−1 in fish and 2.9–5.2 kBq kg−1 in aquatic plants. In the lakes which are used in the fishery, the levels of 90Sr are 0.05–0.5 Bq l−1 in water and 4–550 Bq kg−1 in fish. The levels of 137Cs in these lakes are 0.03–0.6 Bql−1 in water and 2–33 Bq kg−1 in fish. In the first few years following the accident, a dose rate level of 10−2 Gy day−1 to molluscs, bottom-dwelling fish and aquatic plants could be exceeded in the most highly contaminated lakes of Uruskulʹ and Berdyanish. In 1992, the background exposure level for fish from these lakes was still exceeded by a factor of 1000. In the other lakes, the doses to aquatic organisms were considerably lower. Doses to the population from lake fish consumption do not exceed 10−3 Sv year−1.