Long-term variation (1986-1998) of post-Chernobyl 90Sr, 137Cs, 238Pu and 239,240Pu concentrations in air, depositions to ground, resuspension factors and resuspension rates in south Germany

Annual mean concentrations in air and annual total (wet plus dry) depositions to ground of Sr-90, Cs-137, Pu-238 and Pu-239,Pu-240 decreased at Neuherberg, south Germany, in the period from July 1986 (i.e. after the end of the initial deposition phase from Chernobyl) to 1998 as follows: Sr-90 from 0.77 to 0.05 mu Bq m(-3), acid from 0.82 (1988) to 0.28 Bq m(-2) year(-1); Cs-137 from 133 to 2.8 mu Bq m(-3), and from 116 to 3.8 Bq m(-2) year(-1); Pu-238 from 0.95 to 0.063 nBq m(-3), and from 1.0 to 0.23 mBq m(-2) year(-1);Pu-239,Pu-240 from 8.1 to 0.53 nBq m(-3), and from 6.4 to 2.1 mBq m(-2) year(-1). The values for the non-caesium radionuclides are compared to the few available data from other stations. After an initial phase which is characterised for a given radionuclide by the varying ratio of the Chernobyl-derived inventory to the earlier, weapons fallout-derived inventory, the time courses of concentrations of Cs-137, Sr-90, Pu-238 and Pu-239,Pu-240 in air become more or less parallel (from about 1990), despite the considerable differences in the physico-chemical properties of these elements. By contrast, the time series of radionuclide deposition rates show until about 1994 less similarity among each other and with the respective concentration series in air. From 1994, concentrations in air and depositions to ground become nearly constant, or decrease very slowly. At the end of the observation period, resuspension factors between 1.4 x 10(-10) m(-1) and 1.0 x 10(-11) m(-1) are observed for the various nuclides. The time courses of specific activities (Bq g(-1)) as well as the time courses of radionuclide ratios show characteristic differences between air and deposition. The data will be useful in predicting the post-accident behaviour of radionuclides a long time after a large-scale contamination event. (C) 2001 Elsevier Science B.V. All rights reserved.