Radioactive Tracers in the Black Sea: A Tool for Environmental Assessment and Ecological Regulation

Abstract

Radiochemoecological approach has been developed to evaluate a maximum allowable discharge of pollutants into marine environments. It combines assessment of the capability of seawater for self-purification against the nuclear and non-nuclear pollutants, and their toxicity. The rate of decontamination of the waters is estimated from the time-series data on concentration of the fallout radionuclides, both soluble ( 90Sr , 137Cs ) and particle-reactive (239+240Pu). A simple logistic model was developed to describe the effect of self-purification on pollutants concentration that is limited by the maximum allowable concentration (MAC). It is shown that the rate of pollutant discharge into the water body should be decreased when the contamination level has reached exactly ½ MAC. An example of such computation was illustrated regarding the pollution of the Black Sea waters with mercury. The results have showed that the Black Sea assimilation capacity is nearly 40 ton Hg per year, while the Danube discharges alone more than 60 t year−1 mercury, pointing the necessity of an immediate reduction of the Black Sea contamination with this hazardous pollutant.