7Be, 210Pb, airborne particulate matter and PM10 concentrations in relation to meteorological conditions in southern Poland in 1998-2016.

An analysis of the concentration of 7Be in aerosol samples collected in one of the most polluted areas in Europe (Katowice and Krakow in southern Poland) indicated seasonal variability, with a maximum in the summer months. The average concentrations of 7Be were 4616.1 µBq m-3 in Katowice and 3259.4 µBq m-3 in Krakow, respectively, and they are among the highest values recorded in Poland in the studied period (1998-2016). These cities are also characterised by Poland's highest concentrations of 210Pb (547.8 µBq m-3 and 513.2 µBq m-3). The highest radioactive concentrations of 210Pb were observed in the winter and autumn, since in the case of these industrial areas, the combustion processes related to heating in the cold season of the year are an additional source of this isotope, next to its natural origin. The airborne particulate matter concentrations at both locations correlate with the concentrations of 210Pb. The average values of PM10 concentrations (71.1 µg m-3 in Krakow to 45.0 µg m-3 in Katowice), were 2-3 times higher than the average ones recorded in northern Poland. It has been proven that air temperature is the key parameter affecting the transport of isotopes, especially in the warm season of the year, when its increase causes increased thermal convection, leading to intense vertical mixing and exchange in the troposphere. Analyses using the machine learning method allowed for an indication of the correlation between relative humidity and atmospheric precipitation, as well as higher wind speed and concentrations of 7Be which is inversely proportional. Geographical factors (the latitude of the station and the land elevation) have no impact on near-surface concentrations of 7Be in Poland.

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

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).

Correlations between 7Be, 210Pb, dust and PM10 concentrations in relation to meteorological conditions in northern Poland in 1998-2018.

Analysis of a twenty-year (1998-2018) data series on 7Be concentrations in weekly collected aerosol samples in northern Poland showed a clear pattern of seasonal changes in 7Be with a maximum in the summer period associated with the most intensive thermal convection and vertical mixing. Activity concentrations of 7Be ranged from 480 µBq m-3 to 9370 µBq m-3. A strong relationship has been shown between 7Be concentrations observed in years and the activity of the Sun related to the sunspot number. Activity concentrations of 210Pb in aerosol ranged from 17 µBq m-3 to 1490 µBq m-3 with maximum occurring in the winter. The difference in the seasonal pattern in 7Be and 210Pb concentrations were directly related to the different sources of both isotopes, as an additional source of 210Pb was the products of combustion during the heating season. Similar pattern with maximum concentrations in winter was observed for PM10, as the main source is the same as in the case 210Pb. A content of PM10 was in the range from 6.5 to 81.7 µg m-3. A statistically significant correlation between both isotopes occurs. At the same time, 7Be, 210Pb and PM10 are visibly related to the dust concentrations ranged from 7.3 µg m-3 in winter to 134.8 µg m-3 in spring. Statistical analysis carried out with simple regression model, stepwise multiple regression, and Random Forest models showed that the sunspots number, air temperature and sunshine duration have the most substantial impact on transport, and hence the concentration of 7Be in the surface layer of the atmosphere. The increase in relative humidity and precipitation and higher wind speed have a statistically significant effect on the reduction of 7Be concentrations in surface air.