Gross alpha, gross beta activities and gamma emitting radionuclides composition of rainwater samples and deposition to ground

摘要

The radiometric composition of bulk deposition samples, collected monthly in a 5 year period (1 January 2005 until 31 December 2009) at a site located 30 m a.s.l in Malaga (4°28' 8"W; 36° 43'40"N), are analysed in this paper. Measurement of gross alpha, gross beta, artificial and natural radionuclide activity concentrations were carried out in 60 bulk deposition samples. We analysed the time series of gross alpha, gross beta ~7Be, ~(210)Pb and ~(40)K. The specific activities of gross alpha and gross beta measured in bulk deposition material are in the range from 0.012-0.32 and 0.045-1.81 Bq l~(-1) and theirs mean values are: 0.11 and 0.59 Bq l~(-1) respectively. The activity values of ~7Be and ~(210)Pb are in the range from 0.65-8.3 and 0.05-1.32 Bq l~(-1) with mean values of 2.5 and 0.41 Bq l~(-1) respectively. The highest specific activities of ~(40)K in bulk deposition material were recorded in connection with high altitude Saharan dust intrusion. The time variations of the different radionuclide concentrations have been discussed in relation with various meteorological factors and the mean values have been compared to those published in recent literature for other sites located at different latitudes. To study the deposition, monthly deposition data from a funnel collector were compared from 2005 to 2009.The monthly range in deposition fluxes for gross alpha varied widely (0.40-11 Bq m~(-2) month~(-1)) and the average annual deposition is 21 Bq m~(-2) y~(-1). The monthly fluxes for gross beta varied (1.3-33.8 Bq m~(-2) month~(-1)) and the average annual deposition is approximately 120 Bq m~(-2) y~(-1). The total annual deposition fluxes of ~(210)Pb varied between 64.9 and 160.8 Bq m~2 y~(-1) with a mean of 120 Bq m~(-2)y~(-1) The annual ~7Be depositional flux varied between 432 and 1204 Bq m~(-2) y~(-1) with a mean of 676 Bq m~(-2)y~(-1). Observed seasonal variations of deposition data are explained in terms of different environmental features. The atmospheric deposition fluxes of ~7Be and ~(210)Pb were moderately well correlated with rainfall (r~2 of 0.72 and 0.76 respectively) and well correlated one with the other (r~2 of 0.79).