Svetlana A. Terpugova

Lake Baikal is a unique natural object. Study of the composition and optical characteristics of aerosols in the atmosphere above it is an urgent problem. This work analyzes the results of studies of the microstructural and physicochemical properties of near-water and near-ground aerosol in the atmosphere of Lake Baikal basin in summer 2024 onboard Research Vessel Akademik V.A. Koptyug and at the Boyarsky research station on the southeastern coast of the lake. The aerosol spatial distribution over the lake water area and the content of black carbon in aerosol particles are shown to be determined by the location of anthropogenic sources in the absence of smoke plumes from wildfires. Hygroscopicity and volatility of atmospheric aerosols, which depend on aerosol particle size, are studied for the first time. The aerosol condensation activity over the coastal zone is found to be stronger than over the lake. The results can be useful for the development of regional models of atmospheric aerosol.

A description of the designed automated complex is presented. The results of measurements of the content of species with different volatilities in six particle size ranges from 0.3 to 5 μm with artificial heating from 25°С to and 200°С (with an intermediate point at 100°) are discussed. The particle concentration was recorded by an optical counter. The instrumentation complex was tested in the period 2021–2023 in separate series of round-the-clock observations in different seasons. The photoelectric counter and integrating nephelometer measurements in December 2022 and March 2023 were compared. It has been shown that variations in the relative content of soluble sulfur compounds according to the counter data are in a good agreement with the variability of the values of the parameter of condensation activity. In general, the use of this method is hoped to make it possible to obtain additional information about the seasonal and diurnal variations in aerosol composition in the intermediate range of particle sizes.

We consider the results of experimental study of the condensation activity of different-size particles; the study was performed from October 2020 to June 2021, using an AZ-10 photoelectric counter, equipped with a system for artificial humidification of atmospheric aerosol taken from the atmosphere. In parallel, hygrograms of the volume aerosol scattering coefficient were measured, using M903 integrating nephelometer. The atmospheric conditions and aerosol characteristics during the measurement period were typical, confirmed through a comparison with data from multiyear studies of the condensation activity parameter for the scattering coefficient at an angle of 45°.

We present a new development stage of a generalized empirical model of optical characteristics of tropospheric aerosol in Western Siberia. An algorithm is suggested for taking into account the distribution function of absorbing matter and the condensation activity of aerosols as functions of aerosol particle sizes. Optical characteristics have been calculated with the complex refractive index of particles of different sizes variable with the relative air humidity. With aerosol weather types, referred to as “atmospheric haze” type (background and suburban haze), used as an example, the results of retrieving the angular scattering coefficients at small angles and the spectral behavior of the extinction coefficients are compared with experimental data.

Considering the wide range of variability of all aerosol characteristics (especially in the near-ground layer of the atmosphere near industrial centers), when creating a realistic empirical model of optical and microphysical characteristics, the optimal dividing of the total data array according to some multifactor signs is needed. In this paper, we analyze the main states of “dry” aerosol on the basis of the results of long-term regular measurements in the near-ground layer of the atmosphere near the city of Tomsk in 2000–2017. The following parameters were considered: aerosol number concentration and size distribution function, total and angular scattering coefficients, including the small-angle range 1.2° to 20°, mass concentration and size distribution of absorbing substances (equivalent black carbon), characteristics of the aerosol hygroscopic properties, and spectral aerosol extinction of radiation on an open long path in the wavelength range 0.45 to 3.9 µm. In our comprehensive study, we first proposed and developed an original approach (classification) to study the optical and microphysical properties of atmospheric aerosol of various physicochemical origins (background, smoke, smog, anthropogenic, etc.) based on dividing the entire data array into characteristic subarrays (types of aerosol weather), which differ from each other in a different combination of scattering and absorbing properties of particles. To divide the total data array into types of aerosol weather including “Background”, “Haze-S”, “Smog”, and “Smoke haze”, the values of the scattering coefficient of the dry aerosol matter σ_d(λ = 0.51 μm) = 100 Mm⁻¹ and the ratio of the mass concentration of the absorbing substance to the mass concentration of submicron aerosol P = 0.05. The results showed that most of the seasonal average values of the aerosol parameters analyzed in the paper are statistically significantly different when comparing various characteristic types of scattering and absorbing atmospheric aerosol. The results of the research indicate that the application of the developed classification of types of aerosol weather for the analyzed optical and microphysical parameters of aerosol particles is quite effective and reasonable.

The paper presents the generalized empirical model of the aerosol optical characteristics in the lower 5-km layer of the atmosphere of West Siberia. The model is based on the data of long-term airborne sensing of the vertical profiles of the angular scattering coefficient, aerosol disperse composition, as well as the content of absorbing particles. The model provides for retrieval of the aerosol optical characteristics in visible and near IR wavelength ranges (complex refractive index, scattering and absorption coefficients, optical depth, single scattering albedo, and asymmetry factor of the scattering phase function). The main attention in the presented version of the model is given to two aspects: The study of the effect of the size spectrum of the absorbing substance in the composition of aerosol particles on radiative-relevant parameters (the single scattering albedo (SSA) and the asymmetry factor (AF)) and the consideration of different algorithms for taking into account the relative humidity of air. The ranges of uncertainty of SSA and AF at variations in the modal radius of the absorbing fraction at different altitudes in the troposphere are estimated.

Measurement results of a complex of aerosol microphysical, chemical, and optical parameters in two cruises of the Akademik Mstislav Keldysh research vessel in 2016 are analyzed. The work was carried...

Chemical composition of aerosol in the ground layer of the coastal zone in East Antarctica is analyzed in the article. The aerosol samples were taken in 2006–2015 during seasonal works of the Russian Antarctic Expeditions (RAE), namely, these were 52nd–53rd, 55th, and 58th–60th expeditions. Samples were taken in the 200‑km band of the sea-shore zone along routes of the research vessels (REV) «Akademik Fedorov» and «Akademik Treshnikov» as well as on territories of the Russian stations Molodezhnaya and Mirny. Although the results obtained did show the wide range of the aerosol concentrations and a certain variability of their chemical composition, some common features of the variability were revealed. Thus, during the period from 2006 to 2014 a decrease of average values of the sums were noted. Spatially, a tendency of decreasing of the ion concentrations was found in the direction from the station Novolazarevskaya to the Molodezhnaya one, but the concentrations increased from the Molodezhnaya to the station Mirny. The sum of ions of the aerosol in the above mentioned coastal zone was, on the average, equal to 2.44 μg/m3, and it was larger than that on the territory of the Antarctic stations Molodezhnaya (0,29 μg/m3) and Mirny (0,50 ág / m3). The main part to the sum of the aerosol ions on the Antarctic stations was contributed by Na+, Ca2+, Cl−, SO4 2−. The main ions in aerosol composition in the coastal zone are ions Na+ and Cl−. The dominant contribution of the sea salt and SO4 2− can be traced in not only the composition of atmospheric aerosols, but also in the chemical composition of the fresh snow in the coastal areas of East Antarctica: at the Indian station Maitri, on the Larsemann Hills, and in a boring located in 55.3 km from the station Progress (K = 1.4÷6.1). It was noted that values of the coefficient of enrichment K of these ions decreases as someone moves from a shore to inland. Estimation of contributions of the continental and maritime factors to formation of the aerosol chemical composition revealed higher enrichment ratios for K+, Ca2+, SO4 2− (K = 3.6÷13.0). This reflects not only influence of the natural sources, but the intensity of human activities on the Antarctic continent as well. The elemental composition of solid aerosols was also analyzed. The largest concentrations were determined for Zn, Al and Fe. The ratio of concentration of the elements in both the soluble and insoluble phases of the aerosol showed that 84.1% of the total amount of the elements was contained in a water-insoluble state. Fractional relation between the element concentrations changed in different phases from 16 to 98%. High enrichment of the aerosol particles by Zn, Cu, Cr, Ba, Pb, Ni,Se, As, Cd (the enrichment factors = 27÷26 445) had been revealed. The content of dominant chemical components (Na+, Cl−, Zn, Fe), factors and coefficients of the element enrichment in the aerosols as well as in fresh snow of the coastal zone of East Antarctica are indicative of the identity of sources where their composition is formed.

The results of measurements of the aerosol optical thickness (AOT) of the atmosphere by CIMEL Sun–sky radiometers are analysed. In arid zones, days with values of AOT not greater than 0.02 are common. In these cases, the sky radiance in backward hemisphere in the visible wavelength range is practically fully determined by the molecular scattering, which is well studied up to date. This fact opens up possibilities to estimate the errors in measuring sky radiance comparing observed and calculated data, as well as to separate them into random and systematic.

The results of measurements of the dependences of the aerosol optical characteristics on the relative humidity of air in artificial condensation processes are analyzed. The dependences of the condensation growth factors on the dry particle size are calculated and their statistical analysis is performed. The regression relation between the measured optical parameters of condensation activity and the Hanel parameter for the aerosol volume concentration is obtained. The possibility of the estimation of the Hanel parameter from the values of the refractive index of dry and humidified particles is shown.