Geochemical activity of snow and layer-by-layer variability of the isotope ratio (δ18O) in the snow mass under conditions of the different surface atmosphere dustiness

The layered distribution of the isotopic composition (18O) in the snow mass under conditions of different dust pollution of the near-surface atmosphere was studied on the territory of two scientific test sites of the IAO SB RAS: the Fonovaya observatory and the suburban BEK test site (Tomsk). Interlayer differences in isotopic characteristics and the activity of snow chemical reactions were evaluated in conjunction with the analysis of the dispersed composition of the precipitated aerosol substance, the radiation transparency of snow in the UV range, and taking into account reverse trajectories of air mass transfer. Interlayer fluctuations in 18O values were established, the variability of which increased in layers confined to the thermal diffusion geochemical barrier. We suggested that due to the geochemical activity of snow and its ultraviolet transparency, as well as the presence of iron-containing dust-aerosol particles in the snow mass, conditions arose that initiated photoactivated snow-chemical reactions. Their occurrence may be accompanied by free radical oxidation of the precipitated aerosol matter and the formation of stable photoreaction products, which may be evidenced by the established post-sedimentary interlayer differences in the isotope stratification of the snow mass.