Influence of atmospheric circulation and local parameters on activity concentration of gross alpha and gross beta in Granada, Spain

This work analyses the influence of local meteorology and air mass origin on radioactivity levels measured in Granada (Southern Spain). To the scope, gross α and gross β activities at ground-level air were weekly recorded from 2006 to 2021, by collecting aerosol filters and successively analysing them by low-level proportional counting. Time series decomposition shows a strong correlation between the seasonal components of gross α and gross β and the local meteorological parameters, in particular temperature and wind speed. Back trajectories reaching the study area during the sampling, calculated at three height levels (750 m, 1500 m, and 3000 m a.s.l.), were analysed by three methods with the aim to determine the main characteristics of air masses reaching Granada, and their impact on airborne radioactivity levels. The results of the residence time and clustering analyses showed that an increase in the radioactivity levels in the southeast of Spain is connected with air masses coming from the Mediterranean at 750 m and from the South (Sahara Desert) at 3000 m. In line with the outcomes obtained by the cluster analysis, the Concentration Weighted Trajectory (WCWT) results highlight that the air masses transported from Mediterranean and African regions are a potential source of gross α and gross β. Moreover, the findings of the WCWT bring a new aspect by revealing that the southern France region can also have a significant contribution to gross alpha and beta activities.