Cesium-137 and mercury contamination in lake sediments

The contribution of fluvial discharge and global fallout of Cs-137 and mercury to sedimentation fluxes in Lake Shinji and Lake Nakaumi, Japan, was studied. The fluvial flux through soil erosion accounted for 11 to 27% of accumulated Cs-137 in the sediments in the 1950's and 1960's, which were the periods of the most extensive atmospheric input, and for 90 to 100 % in the 1990's. The vertical profiles of mercury concentrations in the lake sediments studied showed a maximum between 1959 and 1963, which was originated mostly from the extensive use of mercury-agrochemicals in paddyfieids of the watershed in the past. These findings are representative examples of long-term contamination of lake sediments caused by the contaminated ground soil erosion. (C) 1999 Elsevier Science Ltd. All rights reserved.