Nuclide-dependent local and collector surface effects in sampling of radioactive deposition to ground

After the end of atmospheric nuclear weapons tests and after the Chernobyl accident, the deposition characteristics of Cs-137 changed from a predomina nt wet deposition to the present resuspension mechanism characterised by pr edominant dry deposition. To study the consequences of this change for depo sition sampling, monthly deposition data from two collectors located at a d istance of 600m were compared from 1991 to 2000. On the average. the Cs-137 , deposition rates differed by roughly a factor of two for whereas for the cosmogenic Be-7 a difference was not detectable with statistical significan ce. Further, a "funnel" collector with a mostly dry surface collected on th e longterm average 36% less of Cs-137, but 8% less of Be-7, than a "pot" co llector with a continuously water-covered surface. Since for Cs-137 deposit ion and the bulk deposition a similar behaviour was found, a stronger sensi tivity of other resuspension-derived radionuclides against local and collec tor surface variations can generally be expected. (C) 2001 Elsevier Science Ltd. All rights reserved.