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Monitoring data on sulfates in atmospheric haze particles over Beijing in winter 2016 are considered. It has been established that the source of sulfates in humidified haze particles is the catalytic oxidation of sulfur dioxide (SO_2(газ)^Mn/Fe,O_2→SO^2-_4(aq)) proceeding in a branched mode. Concentration conditions of this process and the features of its dynamics in the atmosphere are discussed. The agreement between the calculated content of in particles and monitoring data indicates a branched mode of catalytic conversion of SO₂ in the atmosphere - a new source of sulfates. This fast non-photochemical channel should be taken into account in inventory system of sulfate sources in the global atmosphere.

Lichens are not only a bioindicator of air pollution, but they themselves, in turn, affect the chemical composition of the air. The results of studies of the qualitative composition of exometabolites in thalli of epiphytic lichens using the method of high-performance liquid chromatography are presented. A comparative analysis of the fractional composition of deposited aerosol matter in water washouts of lichens showed that it is characterized by a bimodal type of particle distribution. It is postulated that the appearance of the fine fraction is associated with the formation of secondary organic aerosols on the surface of epiphytic lichens. Their precursors are the products of photoactivated reactions between deposited aerosol matter and highly volatile organic compounds that arrive on the surface of lichens as a result of efflorescence. The mechanism of entry of secondary organic aerosols into the surface atmosphere under the influence of radiometric photophoresis is discussed.

One of the possible sources of carbon dioxide entering the atmosphere may be river ecosystems. The paper presents the results of measuring CO₂ fluxes from the surface of a number of rivers and lakes in the Tomsk region. It is shown that during the period of experiments the average carbon dioxide flows for the Ob River were 143.7 ± 21.7 (August 13-14, 2023), 53.3 ± 21.2 (August 19), and 80.4 ± 59.9 mgC × m^-2 × hour^-1 (August 20), respectively. On the river Ket: 66.1 ± 17.3, on the swamp lake Karasevoye 33.3 ± 17.3, on the Suiga River 50.2 ± 23.0, and the Iksa River 81.9 ± 11.5 mgC × m^-2 × hour^-1. Their magnitudes depended significantly not only on the object of study, but also on hydrometeorological conditions.

Cirrus clouds have a significant impact on the radiation balance of our planet and play a crucial role in climate formation. To study their optical properties, it is necessary to address the issue of light scattering by nonspherical ice particles. This article focuses on the numerical simulation of the characteristics of light backscattering for hollow hexagonal columns using the physical optics method. The study examines particles ranging in size from 10 to 316 mm, with wavelengths of 0.355, 0.532, and 1.064 mm. The findings reveal that as the cavity of hexagonal columns increases, the backscattering peak caused by corner reflection rapidly decreases, then several secondary maxima appear, which account for up to 10% of the main peak. At the same time, the position of these secondary maxima remains unaffected by particle size and incident wavelength but is significantly influenced by the particle's shape. These results are valuable for developing an optical model of cirrus clouds and for laser sounding of the atmosphere.

Methods of laser-induced fluorescence and their use in monitoring tools allow solving a number of key problems in the detection of algal blooms. The automated system developed by us makes it possible to process and analyze huge amount of fluorescent spectral characteristics of microalgae monocultures, to determine the dominant monocultures in the water area at the level of genus, and to estimate a possibility of their blooming. In addition, the system makes it possible to catalog reference optical characteristics of microalgae monocultures and to implement interactive algorithms for detecting dangerous microalgae species.

Efficiency of laser radiation harmonic generation in nonlinear crystals is among topical issues in applied nonlinear optics. This work theoretically studies the second harmonic generation (SHG) in a converging (focused into a crystal) laser beam. The influence of the amplitude profile (AP) of fundamental laser radiation beam (before a lens) on the SHG efficiency and on optimal focusing and wave detuning parameters is estimated for the first time. It is ascertained that the optimal values of focusing and especially wave detuning parameters vary in very wide ranges depending on the AP. Strong influence of the AP on the effective aperture length, which mainly limits the SHG efficiency, is shown. Optimization of the AP enables increasing the SHG efficiency by no more than ~ 10%.

The results of describing the spatial distribution of methane concentration in the surface water of Lake Baikal in the spring are presented. The basis was the measurements of CH₄ content which were first carried out in the round-the-clock continuous mode along the entire route of the passage of research vessel in the complex expeditions of LIN SB RAS in the spring seasons of 2013, 2016, 2017, 2018, 2021, and 2022. Based on the results of six expeditions, a data array was compiled; it included 12100 segments (with a step of 0.005° in latitude and 0.01° in longitude) which covered the total area 4466.7 km², or 14% of the Baikal mirror. For a more detailed description of the spatial distribution of methane concentrations in surface water throughout the Baikal water area, the statistical characteristics were calculated in four zones: between 0 and 100 m, 100 and 200 m, 200 and 400 m, and over 400 m isobaths. The comparison of the methane concentrations in the analyzed array with the data of other researchers obtained in different years in close regions of the water area made it possible to conclude that the results presented in the work adequately reflect the most stable features of the spatial distribution of methane concentration in surface water in spring seasons.

The results of studies carried out at the tundra-woodland interface in the Anabar region of the Republic of Sakha (Yakutia) in order to trace the dynamics of permafrost landscapes and identify the influence of vegetation on the soil temperature regime and seasonal thawing depth are presented. The overgrowing of tundra with larch trees took place during the second period of long-term warming in the Arctic (1979-2011). The displacement of tundra communities by woodland communities has changed permafrost conditions in the region. Thus, according to our data, the maximum depth of seasonal thawing is reached in the tundra area; the depth of seasonal thawing decreases with an increase in the woodland density. On the contrary, permafrost temperature has minimum values in the tundra area and increases under woodland. In this paper, the results of the first - stage of the study are presented. Further monitoring studies are planned in the area under consideration.

An overview geocryological map (1:1 M scale) for an area of 136 700 km² covering a significant part of the Bolshezemelskaya tundra was compiled on the basis of large-scale field permafrost-landscape surveys and interpretation of medium-resolution Landsat-7 satellite images. The method of landscape indication implemented in relation to geocryological subzones was used. Spatial variability of geocryological characteristics was analyzed at the levels of natural subzones and groups of dominant landscape units.

Data on the actual maximum area of 71 largest aufeis-taryn in the North-East of Russia (with an area of at least 10 km²) based on the results of interpretation of Landsat satellite images in 2013-2018 (661 km²) and Sentinel-2 in 2020-2021 (838 km²) is presented. The total area of aufeis fields turned out to be at least 2 times lower than the total area of aufeis glades indicated in the Cadaster of aufeis of the North-East (1958) (1680 km²). For 42 objects the area for 1973-1975 were also obtained according to Landsat/MSS data (before the beginning of the warming period). The total value was 555 km², which is close to modern estimates for 2020-2021 (581 km²), and on average. 1.9 times lower than their total area according to the Cadastre (1958) (1083 km²). Despite the fact that individual giant aufeis show very high interannual variability, their area can change up to two times from year to year (100 %), on average for most aufeis fields this value is about 20 %. On numerous examples, a discrepancy between the contours of aufeis glades and the boundaries of aufeis fields was established. The total area of aufeis glades, both indicated in the Cadaster (1958) and identified on the basis of modern space images, significantly exceeds the actual area of aufeis. Estimating the area of aufeis (even the maximum in a long-term period) by the size of aufeis glades can lead to significant errors in the calculation of the dynamic reserves of aufeis groundwater and other characteristics. In the period after 1973-1975 significant change of total aufeis area in the North-East were not identified. Further field studies of giant aufeis are important to identify the causes of their variability, including the establishment of long-term regime observations at special aufeis research plots.