SOURCES OF PRESENT CHERNOBYL-DERIVED CESIUM CONCENTRATIONS IN SURFACE AIR AND DEPOSITION SAMPLES

The sources of Chernobyl-derived caesium concentrations in air and deposition samples collected from mid-1986 to the end of 1990 at Munich-Neuherberg, Germany, were investigated. Local resuspension has been found to be the main source. By comparison with deposition data from other locations it is estimated that within a range from 20 Bq m-2 to 60 kBq m-2 of initially deposited Cs-137 activity approximately 2% is re-deposited by the process of local resuspension in Austria, Germany, Japan and the United Kingdom, while significantly higher total resuspension is to be expected for Denmark and Finland. Stratospheric contribution to the present concentrations is shown to be negligible. This is confirmed by cross correlation analysis between the time series of Cs-137 in air and precipitation before and after the Chernobyl accident and the respective time series of cosmogenic Be-7, which is an indicator of stratospheric input. Seasonal variations of caesium concentrations with maxima in the winter months were observed.