Radiotracers in the Black Sea: A Tool for Marine Environmental Assessments

Post-Chernobyl trends of radioactive contamination of the Black Sea showed a relatively high rate of purification of its waters against soluble and particle reactive radionuclides. The apparent half-lives for the decrease of 137Cs and 90Sr concentrations in the central Black Sea waters was around 6 and 8 years, respectively, suggesting an additional 90Sr input by river runoff. These values, particularly for 137Cs, are considerably lower than in the adjacent Mediterranean basin (∼13 years), which is caused by faster dilution of 137Cs concentration in the upper Black Sea waters due to strong river discharge, and by loss of 137Cs via the Bosporus Strait. These factors, together with a higher rate of particle scavenging of plutonium in the mesotrophic Black Sea water, reflect its significant capability for self-cleaning against nuclear and non-nuclear pollutants, which was traced in this study using data on fluxes and time evolution of natural and anthropogenic radioactivity. (author)