Long-term variation of the concentrations of long-lived Rn descendants and cosmogenic 7Be and determination of the MRT of aerosols

During a 6 years period, the atmospheric activity concentrations of the long-lived 222Rn daughters and 7Be concentrations were measured at Málaga (36° 43′40″ N; 4° 28′8″ W). The concentration data of long-lived radon daughters and 7Be together with meteorological variables were used for a comprehensive regression analysis of weekly variation of radioactivity in air. The seasonal variations of the concentrations show similar trend for the long-lived daughters of radon and 7Be concentrations. The activity concentrations were observed to be higher during the summer months than in other seasons. From the ratio between the activity concentrations of 210Po and 210Pb, a mean residence time of aerosol particles in the atmosphere of about 31 days was obtained. The average concentrations values of 210Pb and 7Be over the 6 years period have been found to be 510 and 4.6 mBq m−3, respectively. A mean aerosol mass concentrations of (46.6±7.8) μg m−3 was also determined during the period of measurements. The 7Be/210Pb activity ratios varied between 11 and 8.4. Correlation study has been carried out between the aerosol mass and concentrations of these tracers.