Temporal variations in radionuclide activity (7Be and210Pb) in surface aerosols at a coastal site in southeastern China

Abstract

Monitoring radionuclides in aerosols is critical to understanding the factors influencing the temporal variations in the atmospheric deposition of elements such as7Be and210Pb, which are frequently used as tracers in atmospheric studies. However, long-term monitoring at a high temporal resolution remains limited, especially in Asia. Therefore, in this study, we measured the radioactivity of the7Be and210Pb in surface aerosols collected on a weekly basis in a coastal city (Xiamen) in southeastern China from 2013 to 2015 (110 samples in total). The activity of the7Be and210Pb ranged from 0.17 to 9.84 mBq m–3 (mean: 4.37 ± 2.65 mBq m–3) and from 0.17 to 3.31 mBq m–3 (mean: 1.26 ± 0.78 mBq m–3), respectively. Compared to reports from other regions, the210Pb activity, on average, was high, which may be related to the elevated226Ra activity in the soil in southeastern China. Also, the annual mean of the7Be activity was significantly correlated with latitude in the coastal region. Despite the difference in origin, the weekly7Be and210Pb activity was significantly correlated (r = 0.679, p < 0.001, n = 110) and showed similar temporal variations, with higher values during the cold dry season. The activity of both radionuclides was negatively correlated with the temperature and precipitation and positively correlated with the fine particle (PM2.5) concentration. The combined effective dose of the7Be and210Pb is approximately 5.7% of the limit for humans; thus, natural radioactivity should be considered as a potential threat to human health, especially in regions with high PM2.5 concentrations.