Deposition patterns of atmospheric 7Be, 210Pb, 40K in cost of west Mediterranean sea, Málaga (Spain)

Abstract

The deposition of radionuclides on the ground is an essential process to understand atmospheric transportation, sedimentation and geological process, being the major removal pathway for airborne particulates. To predict the long-term radiological consequences of an accidental deposition of the radionuclides to the ground, it is a prerequisite to know the environmental long-term behaviour of these radionuclides and a relatively large number of values are required for statistically meaningful conclusions. Nuclides of the natural decay chains, especially for 238U decay chain, are widely applied into atmospheric research, oceanography and marine geology. Atmospheric depositional fluxes of 7Be, 210Pb and 40K were simultaneously measured in monthly interval for eleven years (from January 2005 to December 2015 at Málaga (4 º28´ 8W; 36º 43´40N). Samples were collected monthly in an area of 1 m2 using a collector that is a slightly tilted stainless steel tray and filling 25 or 50 L polyethylene vessels with bulk deposition. The radionuclides present in all samples are 7Be, 210Pb and 40K appears approximately in 50% of the samples. The temporal variations of radionuclides in bulk deposition exhibit similar seasonal behaviour with low values in winter-autumn months and maximum values in spring-summer months. The time variations of the different radionuclides have been discussed in relation to various meteorological factors and the mean values have been compared to those published in recent literature for other sites located at different latitudes. Bulk depositional fluxes of 7Be, 210Pb and 40K have been evaluated for period of measurements. Bulk depositional fluxes of 7Be , 210Pb and 40K varied between 3 and 1779 Bq m-2 month-1 (annual mean = 1247 Bq m-2 year-1 ), and 1 to 102 Bq m-2 year-1 (annual mean = 140 Bq m-2 year-1) and 0,5 to 81 Bq m-2 year-1 ( annual mean = 65 Bq m-2 year-1). Data on the atmospheric depositions of radionuclides in Málaga show clear seasonal variations which can be attributed to the meteorological conditions affecting the transport and deposition processes. The amount of rainfall controls mainly the depositional fluxes. .There is a statistically relationship between 7Be and 210Pb fluxes indicating that removal behaviour from the atmosphere is relatively similar.