The post-Chernobyl budget of Cs-137 and Sr-90 in the Black Sea

Calculations of annual radionuclide budgets in the Black Sea for the period 1986-1995 have been carried out to estimate the contribution of radionucli des of Chernobyl origin to contamination of the Black Sea and to evaluate t he various pathways by which Cs-137 and Sr-90 are introduced into the sea. The scale of radioactive contamination of the Black Sea as a result of the Chernobyl accident is close to that of weapons test contamination. In both cases, the main pathway of Cs-137 and Sr-90 input to the seawater was direc t atmospheric fallout. River runoff brings relatively small amounts of Cs-1 37 info th, Black Sea. The river-derived share of Sr-90 input reached 25% o f its total input for the first 10 years after the accident and continues t o grow. Decreases in the inventory of Cs-137 and Sr-90 in the seawater, cau sed by radioactive decay and their removal through the Bosporus Strait into the Marmara Sea, have been occurring since 1987. In 1994, the Sr-90 invent ory approached the pre-accident level. It is estimated that the Cs-137 inve ntory will reach its pre-accident level by 2025-2030. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.