Artificial radionuclides in sediments of the Don River Estuary and Azov Sea

The Don River Estuary–Azov Sea system is an extension of the shallow continental shelf area of the Black Sea. A large data set of artificial radionuclides in bottom sediments of the Azov Sea has been compiled in order to examine the storage and migration of radionuclides within this highly restricted inland sea and to estimate the annual dose received by individuals in the local population who regularly consume fish. In recent years (1997–1999), the radionuclide content of surface sediments has been: 137Cs 0.5–100 Bq/kg d.w. (mean=33.8±25.9 Bq/kg d.w., n=57), 90Sr=0.2–5.7 Bq/kg d.w. (mean=2.1±1.4 Bq/kg d.w., n=34) and 239,240Pu=0.31–0.51 Bq/kg d.w. (n=2). In general, 137Cs activities increase with distance from the mouth of the Don River and correlate negatively with sediment grain size (r2=0.77, n=21). The annual 137Cs-derived dose received by an individual through the trophic chain water–fish–humans (≈10−6 Sv/yr) is well below regulatory recommended limits, indicating that current levels of radioactivity in the environment pose no threat to commercial fisheries operations for the bordering nations of Russia and Ukraine.