Be-7 and Pb-210 in fallout and aerosols in 2000–2016 in central Europe — Deposition velocity and dependence on meteorological parameters

Abstract

The main aim of this research was to determine the transport and deposition velocities of 7Be and 210Pb based on a vast database containing the results of measurements of 7Be and 210Pb in fallout and aerosol samples carried out at several stations located throughout Poland in the period from 2000 to 2016. The monthly deposition flux of 7Be and 210Pb showed an unequivocal downward trend but was also subject to seasonal changes, with maximum values in the summer period. The same patterns were found in the case of the deposition rate, the average values of which were 0.7 cm s−1 for 7Be and 0.5 cm s−1 for 210Pb. A strong, statistically significant dependence of the deposition rate on the amount of dust was demonstrated, whereby a 10 μg m−3 decrease in dust increases the 7Be deposition rate by 0.1 cm s−1. Reduction of the concentration of carrier particles reduces the share of dry deposition in favour of precipitation convection, which is much more significant for the transport of both isotopes to the surface. Study of the effect of meteorological parameters showed that the concentrations of 7Be in fallout and aerosol samples and 210Pb in fallout increase with increasing temperature, indicating a significant share of convection processes in isotope transport. The concentrations of 210Pb in aerosols did not show any significant statistical changes over time. Their maximum values were observed in the winter period, indicating an additional source of this isotope related to combustion processes in the heating season. The studies confirmed the dominant role of convective precipitation and large-scale precipitation processes in the elution of 7Be from the atmosphere by showing the monthly deposition of this isotope to be strongly dependent on the total precipitation (r = 0.618).