Peculiarities of the chemical composition of size-segregated atmospheric aerosols sampled at Fonovaya Observatory, West Siberia

Aerosols play an important role in radiation processes in the atmosphere, as well as they have a significant impact on global and regional air quality. The process of the atmospheric nanoparticle formation starts from in situ conversion of condensable vapors. Then, the freshly formed nanometer-size clusters begin to grow due to the condensation of nucleating vapours on them and a self-coagulation as well, thus reaching the optically active size ranges. The relative contribution of the above mechanisms can be estimated by the chemical composition of size-segregated particles. Here, we present preliminary results of the analysis of aerosol samples characterizing the inorganic chemical composition of particles ranging from a few nm to 10 mm. The sampling was performed at Fonovaya Observatory (West Siberia) in October 2021 by means of the Model 125R Nano-MOUDI Impactor.

The analysis showed that in the lowest size range (<10 nm), only five ions were detected: SO₄^2-, Cl^-, K⁺, Na⁺, H⁺. The growth of the nucleation mode particles to the size range of 60-100 nm was accompanied by increasing content of SO₄^2-, Na⁺, H⁺ ions to 50, 37 and 13%, respectively, suggesting the condensation of H₂SO₄ vapours or the coagulation of particles contained mainly Na₂SO₄. A content of ammonium ions (NH₄⁺) appeared to be significant only in the accumulation mode size range (0.1-1.0 mm). Nitrates (NO₃^-) were detected mainly in the Aitken mode particles and then their contribution increases in accumulation and coarse mode ranges.

This work was supported by the RFBR grant No. 19-05-50024 (Microparticles in the atmosphere: formation and transformation in the atmospheric surface layer and in the free troposphere, radiation effects and impact on public health).