Radiocaesium in the sediments of Øvre Heimdalsvatn, a Norwegian subalpine lake

Lake sediment cores and samples of stream sediments from the catchment of Øvre Heimdalsvatn have been collected. The lake sediments exhibit apparently unsystematic spatial distribution of radiocaesium. This is ascribed to irregular bathygraphy. However, the radiocaesium concentration increased with increasing percentage of organic matter, water content, and with distance from the main inlet. There was no correlation with lake depth. Stream sediments were scarce because of torrential conditions but those present had activities in line with the lake sediments. Therefore they constitute a small potential for further supply of radiocaesium to the lake. Measurements of export from the catchment and retention in the lake show that the total radiocaesium activity in the sediments may remain unchanged or even increase during the years to come.