Long‐term variation (1992–1999) of gross‐beta, 210Pb and 90Sr concentrations in rainwater and deposition to ground

Abstract

After the end of atmospheric nuclear weapons tests and after the Chernobyl accident, the deposition characteristics of radionuclides changed from a predominant wet deposition to the present resuspension mechanism characterised by predominant dry deposition. To study the deposition, monthly deposition data from a collector located at a coastal station (Málaga, South Spain) were compared from 1992 to 1999. The measurement of artificial and natural radionuclide activity concentrations in bulk deposition material by non‐destructive ultra low‐level gamma‐ray spectrometry and long‐term deposition fluxes at this sampling site are reported. The range in annual fluxes for gross‐beta is 60.1–97.2 Bq m−2 yr−1. A measure of the annual deposition velocity for the total beta activity has been obtained using specific concentrations in air and deposition fluxes. The annual total deposition fluxes of 210Pb varied between 12.4 Bq m−2 [1998] and 464.15 Bq m−2 [1996], showing a minimum in the years 1994, 1995 and 1999. The average atmospheric fallout value for 210Pb (135.7 Bq m−2 yr−1) measured over 8 years (1992–1999) is compared with values from other stations. The annual total deposition fluxes of 90Sr varied between <2.15 Bq m−2 [1999] and 13.3 Bq m−2 [1994], showing a significant decrease as expected for natural removal and radioactive decay and no new releases from nuclear facilities or weapons testing.