Be-7 and Pb-210 in fallout and aerosols in 2000-2016 in central Europe - Deposition velocity and dependence on...

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).