Be-7, Pb-210 and K-40 depositions over 11 years in Malaga

摘要

The monthly bulk depositional fluxes of three natural radionuclides (Be-7, Pb-210 and K-40) were measured at a Mediterranean coastal station (Malaga) over an 11-year period from 2005 to 2015. The mean annual depositional fluxes of Be-7, Pb-210 and K-40 were 1215, 144 and 67 Bq M-2 year(-1) respectively, showing a clear seasonal trend with minimum values recorded during summer and maximum values in winter. The rainfall regime with dry summers allows estimating the dry deposition. Assuming constant dry deposition through each year, Be-7, Pb-210 and K-40 would account for 12.5, 26.5 and 33% of the bulk fallout respectively which indicates that deposition for Pb-210 and K-40 are significantly higher than Be-7. The precipitation-normalized enrichment factor alpha used to explain seasonal variations in the depositional fluxes of radionuclides with respect the rainfall, indicates higher depositional fluxes during spring and summer than expected from the amount of rainfall. Despite their different origin, Pb-210 and Be-7 monthly depositional fluxes have strong correlation. The atmospheric deposition fluxes of Be-7, Pb-210 and K-40 were controlled mainly by the amount of rainfall (r = 0.89, 0.91 and 0.66 respectively). Moreover, principal component analysis was applied to the datasets and deposition of radionuclides and rainfall in the same component highlighting the importance of the washout mechanism. The mean depositional velocity of aerosols evaluated using Be-7 and Pb-210 are similar and are compared to other published values. (C) 2017 Elsevier Ltd. All rights reserved.