The radionuclide composition of the atmospheric precipitations (rain and snow) fell out on the territory of the South of the Western Siberia in 2016-2017 was studied. It is shown that, the maximum of deposition of 7Be and 210Pb were observed in a foothill zone (618 and 171 Bq/m2), the minimum in the Alpine zone (104 and 27 Bq/m2), for the forest-steppe zone these values are 237-340 Bq/m2 and 73-93 Bq/m2. Deposition density of 137Cs in comparison with 210Pb and 7Be is small and does not exceed 1 Bq/m2. Average values of total specific activities of 210Pb and 7Be in rain waters are 242 and 2434 mBq/l, in the snowmelt 506 and 1611 mBq/l. 7Be/210Pb activity ratio in rain waters more than three times higher, than in snowmelt: 10,1 to 3,2. The highest values of 7Be/210Pb activity ratios are observed in the finest fraction (<0.45 µm) of the suspended matter: 19 in rain and 10 in snowmelt waters.
Radioactive isotopes (7Be, 210Pbatm and 137Cs) are used as indicators of processes associated with the transfer of matter from the atmosphere. Studying snow cover can provide information about the seasonal deposition flux of the isotopes to the Earth’s surface over the entire period of snow accumulation. The purpose of this study is to identify the features of 7Be, 210Pbatm and 137Cs deposition with the atmospheric precipitation in winter in the Arctic part of Western Siberia and to study the contribution of the particulate fractions of suspended matter in snow water to the total content of the radionuclides in samples of integrated seasonal snowfall. Snow samples were taken over a wide area along the highways around Novy Urengoy in April 2019. The suspended matter in snow samples was divided into three fractions. The isotopic composition was determined by high-resolution semiconductor gamma-spectrometry. The seasonal deposition flux of 7Be and 210Pbatm in the winter at the time of sampling averaged 58.7 and 25.2 Bq m−2 season−1, respectively. The average specific activity of 7Be and 210Pbatm in the snow water was 248.0 and 104.5 mBq L−1. The deposition flux of 137Cs from the atmosphere was low compared to 7Be and 210Pbatm and did not exceed 0.39 Bq m−2 season−1 at all sampling points. This indicates an insignificant modern flux of the radionuclide from the atmosphere. The separation of suspended matter in snow water by particulate fractions shows that the studied isotopes are present in all the extracted fractions: >3, 0.45–3 and <0.45 μm. The main part of 210Pbatm in all studied samples is in the coarse-grained fraction >3 μm. Most 7Be is contained in finely dispersed aerosols, colloids, or a dissolved component (where the fraction <0.45 μm). A significant increase in the contribution of coarse-grained fractions of suspended matter in snow water to the total activity of 7Be in snow precipitation was observed in territories with a higher anthropogenic impact.
Annual needles of larch and cedar were sampled in the tundra zone of the Arctic part of Western Siberia in order to determine 7Be, 210Pb and 137Cs specific activities. Higher concentrations of 137Cs in the needles of cedar relative to the needles of larch can be associated with a clear difference in the properties of accumulation and translocation of caesium among these species. Higher concentrations of 7Be and 210Pb in the needles of larch relative to cedar needles and close isotopic ratios (7Be/210Pb) are probably due to more efficient aerosol deposition on vegetative canopies of larch.
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