Radiocaesium removal from European lakes and reservoirs: Key processes determined from 16 Chernobyl-contaminated lakes

A study based on information from the scientific literature was carried out to identify the key processes which determine the initial radiocaesium act ivity concentration and its rate of removal in 16 different European lakes after the Chernobyl accident. Analysis and modelling of these data showed t hat a simple model, incorporating only dilution, lake hushing and settling of suspended particles, can explain 97% of the variation in initial activit y concentrations in lakewater and 79% of the variation in Cs-137 removal ra tes. On the basis of currently available data, incorporating a simple model for removal of activity by diffusion across the sediment-water interface d id not improve model predictive power. It is shown that direct diffusion wa s of less importance in determining radiocaesium removal rates than particl e settling. The potassium concentration of the lakewater was found to have a significant, negative, covariance with Cs-137 removal rates. The relation ship between [K+] and removal rate is shown to be quantitatively consistent with previous studies on the binding mechanism of Cs-137 to particulates. (C) 1999 Elsevier Science Ltd. All rights reserved.