⁷Be, ²¹⁰Pb_atm and ¹³⁷Cs in Snow Deposits in the Arctic Part of Western Siberia (Yamal-Nenets Autonomous District)

Radioactive isotopes (⁷Be, ²¹⁰Pb_atm 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, ²¹⁰Pb_atm 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 ²¹⁰Pb_atm 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 ²¹⁰Pb_atm 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 ²¹⁰Pb_atm 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 ²¹⁰Pb_atm 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.