Загрязнение поверхности снега полициклическими ароматическими углеводородами при образовании изморози

When analyzing chemical compositions of snow the high variability of content of polycyclic aromatic hydrocarbons (PAHs) in snow cover between snowfalls is observed. Researchers explain this by concentrating of snow. However, another mechanism of atmospheric contamination of the snow cover surface is possible. It may be a precipitation of fine crystals of PAHs from the atmosphere in the composition of cryohydrates, which can form aerogenic anomalies on the snow surface at formation of hoarfrost. The process starts in the atmosphere during the interaction of finely dispersed crystals of PAHs with cloud supercooled drops. This results in the cryogenic concentration of solid particles of PAHs by way of formation of solid eutectic mixture – cryohydrates, which are a two-phase system consisting of a fine mixture of crystals of solid particles and ice. Evidence of their manifestation is the presence of the Forel hatching on the surface of the facets of the hoarfrost crystals appearing due to the different optical density of alternating zones, which consist of interpenetrating domains of crystallized solid aerosols and ice. At the same time, due to the presence of temperature inversion over the snow cover and its drying effect on the near-snow layer of air, a stable mass transport of water vapor down to the snow cover is formed, which can initiate the flow of fine cryohydrates from the PAHs. Therefore, the growth of atmospheric ice crystals, begun in the surface atmosphere, continues on the snow surface during formation of hoarfrost, thus creating a special nano-relief of snow cover. The paper presents the results of observations of changes in the concentration of individual PAHs in the upper 18 mm layer of snow at accumulation of the surface hoarfrost during a long period between snowfalls. Some micro-morphological features of the forms of skeletal rime micro-crystals are shown, with which an increase in the nano-roughness of the snow surface is associated, as well as the manifestation of the signal of the aerogenic PAH anomaly on the snow surface. Since the conditions for the formation of surface hoarfrost occur more often than for snowfalls, the hoarfrost may be an informative object of testing when detecting hydrocarbon contamination of snow cover during the intervals between snowfalls.Рассматриваются физические свойства снежного покрова, контролирующие механизм загрязнения снежного покрова полициклическими ароматическими углеводородами при образовании поверхностной изморози. Показаны некоторые микроморфологические признаки различных форм скелетных кристаллов изморози, участвующих в указанном процессе. Обсуждается механизм загрязнения поверхности снежного покрова, связанного с атмосферным стоком тонкодисперсных кристаллов полициклических ароматических углеводородов в составе криогидратов

Pollution of the snow surface with polycyclic aromatic hydrocarbons during the formation of frost

When analyzing chemical compositions of snow the high variability of content of polycyclic aromatic hydrocarbons (PAHs) in snow cover between snowfalls is observed. Researchers explain this by concentrating of snow. However, another mechanism of atmospheric contamination of the snow cover surface is possible. It may be a precipitation of fine crystals of PAHs from the atmosphere in the composition of cryohydrates, which can form aerogenic anomalies on the snow surface at formation of hoarfrost. The process starts in the atmosphere during the interaction of finely dispersed crystals of PAHs with cloud supercooled drops. This results in the cryogenic concentration of solid particles of PAHs by way of formation of solid eutectic mixture – cryohydrates, which are a two-phase system consisting of a fine mixture of crystals of solid particles and ice. Evidence of their manifestation is the presence of the Forel hatching on the surface of the facets of the hoarfrost crystals appearing due to the different optical density of alternating zones, which consist of interpenetrating domains of crystallized solid aerosols and ice. At the same time, due to the presence of temperature inversion over the snow cover and its drying effect on the near-snow layer of air, a stable mass transport of water vapor down to the snow cover is formed, which can initiate the flow of fine cryohydrates from the PAHs. Therefore, the growth of atmospheric ice crystals, begun in the surface atmosphere, continues on the snow surface during formation of hoarfrost, thus creating a special nano-relief of snow cover. The paper presents the results of observations of changes in the concentration of individual PAHs in the upper 18 mm layer of snow at accumulation of the surface hoarfrost during a long period between snowfalls. Some micro-morphological features of the forms of skeletal rime micro-crystals are shown, with which an increase in the nano-roughness of the snow surface is associated, as well as the manifestation of the signal of the aerogenic PAH anomaly on the snow surface. Since the conditions for the formation of surface hoarfrost occur more often than for snowfalls, the hoarfrost may be an informative object of testing when detecting hydrocarbon contamination of snow cover during the intervals between snowfalls

Air Composition over the Russian Arctic: 1—Methane

In the Arctic, global warming is 2–3 times faster than over other regions of the globe. As a result, noticeable changes are already being recorded in all areas of the environment. However, there is very little data on such changes in the Russian Arctic. Therefore, to fill the gap in the data on the vertical distribution of the gas and aerosol composition of air in this region, an experiment was carried out on the Tu-134 Optik flying laboratory in September 2020 to sound the atmosphere and water surface over the water areas of all seas in the Russian Arctic. This paper analyzes the spatial distribution of methane. It is shown that during the experiment its concentration was the highest over the Kara Sea (2090 ppb) and the lowest over the Chukchi Sea (2005 ppb). The East Siberian and Bering Seas were slightly different from the Chukchi Sea in terms of the methane concentration. Average values of CH4 are characteristic of the Barents (2030 ppb) and the Laptev Seas (2040 ppb). The difference between the concentrations at an altitude of 200 meters and in the free troposphere attained 150 ppb over the Kara Sea, decreased to 91 and 94 ppb over the Barents and Laptev Seas, and further decreased over the East Siberian, Chukchi, and Bering Seas to 66, 63, and 74 ppb, respectively. Horizontal heterogeneity in the distribution of methane over the Arctic seas is the greatest over the Laptev Sea, where it attained 73 ppb. It is two times higher than over the Barents and Kara Seas, and 5–7 times higher than over the East Siberian and Bering Seas

Comparison of Distributions of Atmospheric Gas Admixture Concentrations Measured by Remote and In Situ Instruments over the Russian Sector of the Arctic

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Air Composition over the Russian Arctic: 2–Carbon Dioxide

International audienceWe analyze the spatial distribution of carbon dioxide over the seas of the Russian Arctic based on the results of the comprehensive experiment conducted in September 2020. It turned out that during the experiment, the concentration of CO2 increased from west to east. The minimum of 396 ppm was over the Barents Sea, and the maximum of 4106 ppm was over the Chukchi Sea. The difference between the concentrations at an altitude of 200 m and in the free troposphere attained 156 ppm over the Barents Sea and decreased to 56 ppm over the Laptev Sea. Over the eastern seas, the difference became generally positive, which was associated with the air transfer from Alaska. Above the waters of most seas, the distribution of carbon dioxide was horizontally heterogeneous, which showed the regional features of its assimilation by the ocean and transfer from the continent

Complex experiment on studying the microphysical, chemical, and optical properties of aerosol particles and estimating the contribution of atmospheric aerosol-to-earth radiation budget

The primary objective of this complex aerosol experiment was the measurement of microphysical, chemical, and optical properties of aerosol particles in the surface air layer and free atmosphere. The measurement data were used to retrieve the whole set of aerosol optical parameters, necessary for radiation calculations. Three measurement cycles were performed within the experiment during 2013: in spring, when the aerosol generation is maximal; in summer (July), when atmospheric boundary layer altitude and, hence, mixing layer altitude are maximal; and in late summer/early autumn, during the period of nucleation of secondary particles. Thus, independently obtained data on the optical, meteorological, and microphysical parameters of the atmosphere allow intercalibration and inter-complement of the data and thereby provide for qualitatively new information which explains the physical nature of the processes that form the vertical structure of the aerosol field

Distribution of trace gases and aerosols in the troposphere over West Siberia and Kara Sea

International audienceThe Arctic is affected by climate change much stronger than other regions of the globe. Permafrost thawing can lead to additional methane release, which enhances the greenhouse effect and warming, as well as changes of Arctic tundra ecosystems. A great part of Siberian Arctic is still unexplored. Ground-based investigations are difficult to be carried out in this area due to it is an out-of-the-way place. So, in spite of the high cost, aircraft-based in-situ measurements can provide a good opportunity to fill up the gap in data on the atmospheric composition over this region