A comparative study of 7Be in total suspended particles (TSP) and PM10

Abstract

This study evaluates potential differences in 7Be activity concentrations measured using two aerosol sampling systems equipped with PM10 and total suspended particles (TSP) inlets under real atmospheric conditions. During the study period, mean 7Be activity concentrations were 4.4 ± 1.4 mBq m−3 for PM10 and 3.7 ± 1.2 mBq m−3 for TSP samples. A strong temporal correlation was observed between both datasets (ρ = 0.882, p < 0.001), indicating consistent response to atmospheric variability. Although individual weekly differences are not always statistically significant when measurement uncertainties are considered, the overall distribution revealed a systematic tendency toward higher 7Be concentrations in the PM10 fraction, with relative differences ranging from 4% to 44%, consistent with the preferential association of 7Be with fine aerosol particles. Six sampling weeks showed higher 7Be values in TSP than in PM10, but only three met the criterion for statistically significant difference. Back-trajectory analysis showed that only one sampling week corresponded to a well-defined Saharan dust intrusion, whereas the two other cases were more linked to regional resuspension processes and accumulation of locally or regionally derived coarse particles that may enhance the relative contribution of the TSP fraction. These findings indicate that episodic increases of 7Be in the TSP fraction may arise from both mineral dust advection and locally driven coarse-particle accumulation. Multivariate analysis identified two dominant atmospheric regimes controlling radionuclide variability. The first component linked 7Be concentrations with temperature and wind direction, reflecting the influence of large-scale atmospheric transport and vertical mixing processes. The second component grouped dust concentrations and wind speed, indicating the importance of mechanically driven aerosol resuspension and transport. Overall, the results demonstrate that while PM10 and TSP sampling systems provide highly comparable measurements of atmospheric 7Be activity, differences in particle size distribution during dust transport episodes can lead to systematic variations between both fractions. These findings highlight the importance of considering inlet-dependent size selectivity when comparing long-term radionuclide records obtained using different aerosol sampling configurations.