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Abstract. The change of the global climate is most pronounced in the Arctic, where the air temperature increases 2 to 3 times faster than the global average. This process is associated with an increase in the concentration of greenhouse gases in the atmosphere. There are publications predicting the sharp increase in methane emissions into the atmosphere due to permafrost thawing. Therefore, it is important to study how the air composition in the Arctic changes in the changing climate. In the Russian sector of the Arctic, the air composition was measured only in the surface atmospheric layer at the coastal stations or earlier at the drifting stations. Vertical distributions of gas constituents of the atmosphere and aerosol were determined only in a few small regions. That is why the integrated experiment was carried out to measure the composition of the troposphere in the entire Russian sector of the Arctic from on board the Optik Tu-134 aircraft laboratory in the period of ​​​​​​​4 to 17 September of 2020. The aircraft laboratory was equipped with contact and remote measurement facilities. The contact facilities were capable of measuring the concentrations of CO2, CH4, O3, CO, NOx​​​​​​​, and SO2, as well as the disperse composition of particles in the size range from 3 nm to 32 µm, black carbon, and organic and inorganic components of atmospheric aerosol. The remote facilities were operated to measure the water transparency in the upper layer of the ocean, the chlorophyll content in water, and spectral characteristics of the underlying surface. The measured data have shown that the ocean continues absorbing CO2. This process is most intense over the Barents and Kara seas. The recorded methane concentration was increased over all the Arctic seas, reaching 2090 ppb in the near-water layer over the Kara Sea. The contents of other gas components and black carbon were close to the background level. In bioaerosol, bacteria predominated among the identified microorganisms. In most samples, they were represented by coccal forms, less often spore-forming and non-spore-bearing rod-shaped bacteria. No dependence of the representation of various bacterial genera on the height and the sampling site was revealed. The most turbid during the experiment was the upper layer of the Chukchi and Bering seas. The Barents Sea turned out to be the most transparent. The differences in extinction varied by more than a factor of 1.5. In all measurements, except for the Barents Sea, the tendency of an increase in chlorophyll fluorescence in more transparent waters was observed.

To contribute to the comprehensive study of atmospheric pollution in Siberia, aircraft soundingwas carried out in Northwestern Siberian along the following route: Novosibirsk – Surgut – Igarka – Novosibirsk. This work was aimed at studying the quantity and representation of culturable microorganisms and other biogenic components of the atmosphere at altitudes up to 8,000 m. The air samples were collected to impingers (flow rate 50 ± 5 L/min) where 50 ml of Hanks’ solution (ICN Biomedicals) was used as the sorbing liquid and applied on the fibrous filters. The concentration of biogenic material was recorded, and the concentration and diversity of culturable microorganisms were determined in total protein samples. It was found that the samples of atmospheric air contained 158 mesophilic and psychrophilic microorganisms represented by such genera as Micrococcus, Staphylococcus, Bacillus, Nocardia, Arthrobacter, and Rhodococcus. Also, Actinomycete, yeast and fungal cultures were also iso-lated. Non-sporiferous bacteria were widely presented at all altitudes. Enzymatic activity of the isolated microorganisms and a number of pathogenicity factors present were investigated. The data on quantity and representation of culturable microorganisms and other biogenic components at altitudes up to 8000 m in Northwestern Siberia were obtained for the first time. It is a significant contribution to the study of the atmosphere of this region. The patterns of the observed biodiversity of microorganisms, associated with the sampling altitude or geographic location, should be determined infurther research.

Abstract. The change of the global climate is most pronounced in the Arctic, where the air temperature increases two to three times faster than the global average. This process is associated with an increase in the concentration of greenhouse gases in the atmosphere. There are publications predicting the sharp increase of methane emissions into the atmosphere due to permafrost thawing. Therefore, it is important to study how the air composition in the Arctic changes in the changing climate. In the Russian sector of the Arctic, the air composition was measured only in the surface atmospheric layer at the coastal stations or earlier at the drifting stations. Vertical distributions of gas constituents of the atmosphere and aerosol were determined only in few small regions. That is why the integrated experiment was carried out to measure the composition of the troposphere in the entire Russian sector of the Arctic from onboard the Optik Tu-134 aircraft laboratory in the period of September 4 to 17 of 2020. The aircraft laboratory was equipped with contact and remote measurement facilities. The contact facilities were capable of measuring the concentrations of CO2, CH4, O3, CO, NOX, and SO2, as well as the disperse composition of particles in the size range from 3 nm to 32 µm, black carbon, organic and inorganic components of atmospheric aerosol. The remote facilities were operated to measure the water transparency in the upper layer of the ocean, the chlorophyll content in water, and spectral characteristics of the underlying surface. The measured data have shown that the ocean continues absorbing СО2. This process is most intense over the Barents and Kara Seas. The recorded methane concentration was increased over all the arctic seas, reaching 2090 ppb in the near-water layer over the Kara Sea. The contents of other gas components and black carbon were close to the background level. In bioaerosol, bacteria predominated among the identified microorganisms. In most samples, they were represented by coccal forms, less often spore-forming and non-spore-bearing rod-shaped bacteria. No dependence of the representation of various bacterial genera on the height and the sampling site was revealed. The most turbid during the experiment was the upper layer of the Chukchi and Bering Seas. The Barents Sea turned out to be the most transparent. The differences in extinction varied more than 1.5 times. In all measurements, except for the Barents Sea, the tendency to an increase in chlorophyll fluorescence in more transparent waters was observed.

<p>In 2020, a unique experiment, which had ever been implemented either in the former USSR or in modern-day Russia, was carried out in the Russian Arctic by means of the Optik Tu-134 aircraft laboratory operated by IAO SB RAS. The airborne measurement campaign was conducted on September 4-17 over all seas and coastal regions of the Russian sector of the Arctic, including northern part of the Bering Sea.</p><p>During the flights, in situ measurements of CO, CO<sub>2</sub>, CH<sub>4</sub>, NO, NO<sub>2</sub>, SO<sub>2</sub>, O<sub>3</sub>, aerosols, and black carbon (BC) were performed. Air samples were taken to determine organic and inorganic compounds and biological material in aerosol particles. A remote sensing of the water turbidity in the upper sea layers was conducted by means of the LOZA-2 lidar that allowed a concentration of plankton to be derived there. Spectral characteristics of the water and underlying coastal surfaces were measured using a spectroradiometer.</p><p>The primary analysis of the obtained data showed that concentrations of CO, NO, NO<sub>2</sub>, SO<sub>2</sub>, O<sub>3</sub>, aerosols, and BC during the experiment were low that is typical for background regions. CO<sub>2</sub> mixing ratios in the lowest part of the troposphere above seas were lower than aloft. As compared with coastal areas, concentration of methane over all the seas of the Arctic sector and the Bering Sea was higher.</p><p>We would like to acknowledge our colleagues from the following organizations for their assistance in organizing and conducting this campaign, and in particular, Laboratoire des sciences du climat et de l'environnement and Laboratoire atmosphères, milieux, observations spatiales (France); Finnish Meteorological Institute and Institute for Atmospheric and Earth System Research, University of Helsinki (Finland); Center for Global Environmental Research at the National Institute for Environmental Studies (Japan); the National Oceanic and Atmospheric Administration, US Department of Commerce (USA); Max-Planck-Institute for Biochemistry (Germany); and University of Reading (UK).</p>