Environmental recovery from radiocesium-contaminated Japanese and European coastal waters

Abstract

we present spatiotemporal distributions of Cs-137 in the Baltic Sea, the North Sea, and the Norwegian Sea, for which a large quantity of data are available, and those in the Japanese coastal waters. The effective half-lives 1 to 9 years after each accident were shortest (1.6-4.7 y) in Japanese coastal waters, 4.9 y in the North Sea, and 14.4 y in the Baltic Sea, suggesting that decreases in Cs-137 concentrations are largely dependent on the local geography, and that the dilution-diffusion effect of seawater was greater in the Japanese coastal waters. The effective half-lives of Cs-137 in the surface waters of European seas, based on 30 years of data after the CNPP accident, became longer, ranging from 8.4 to 11.9 y. This may be due to the influence of rivers, and a delay in the decrease in Cs-137 levels caused by the small difference in radioactivity concentrations between the seas and diluting waters.