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Results of the analysis of interannual, seasonal, and diurnal variations in the ratios of the mixture of CH4, CO2, CO, benzene, and δ13C–CH4 in the surface air of Moscow based on the measurements at the station of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS), in 2018–2020 are presented. The annual maximum concentration of CH4, CO2, and CO (>2.2, 430, and 0.20 ppm, respectively) occurs in the winter months due to the seasonal increase in the anthropogenic load from the main sources of urban pollution: motor transport and thermal power plants and a decrease in the role of vertical air mixing. The greatest contribution of local and remote microbial sources to the CH4 concentration is noted in the summer months against the background of low δ13C–CH4 values (–50 to –60‰). In all seasons, CH4, CO2, and CO ground level peaks lasting up to several hours are due to the transport from industrial sites in the E–SE sector. The calculated mean emission ratios in urban air were CH4/benzene = 0.52–0.54 ppm/ppb, CH4/СО = 0.56–0.75 ppm/ppm, CO2/benzene = 77–93 ppm/ppb, CO2/СО = 81–131 ppm/ppm, and CO/benzene = 0.65–1.11 ppm/ppb. These ratios characterize the predominant contribution of emissions from motor transport and the heat and power equipment and can be used to refine the absolute values of emissions, including those on the basis of existing inventories of sources of anthropogenic air pollution. [ABSTRACT FROM AUTHOR]

We have studied the assessment of methane content in the near atmospheric layer of the Arctic seas and the sources of its emissions. Continuous atmospheric measurements of methane concentration and δ13C isotope signature in methane were carried out during two expeditions aboard the R/V Akademik Mstislav Keldysh in the summer and autumn of 2020. The minimum CH4 concentration (mean 1.937 ± 0.010 ppm) were obtained over the North and Norwegian Seas. The maximum CH4 concentration took place above the Kara (1.998 ± 0.030 ppm on average, maximum values are up to 2.000–2.040 ppm) and White (2.006 ± 0.030 ppm on average) seas. The average values of δ13C in the studied region were close to that typical for the Northern Hemisphere: –47.5‰. Regional changes in δ13C allowed CH4 sources to be identified and showed that the methane concentration in the surface atmospheric level is mainly affected by the direction of air-mass advection. [ABSTRACT FROM AUTHOR]

We have investigated the variability of smoke aerosol absorbing ability with variations in the content of brown carbon (BrC) and black carbon (BC). Using monitoring data on radiative characteristics of smoke aerosol at AERONET stations and the spatial distribution of aerosol optical depth (AOD) obtained by the MODIS spectrometer (Terra satellite), we have detected large-scale smokes during boreal forest fires in Russia and Canada (1995-2012). The spatial distribution (50°-70° N, 95°-125° W) and temporal variability (at AERONET station Fort McMurray) of AOD during the smoking of a part of Canada in July 2012 have been analyzed. AOD probability distributions for July 14-18, 2012, and an estimate of aerosol radiative forcing of smoke aerosol at the upper boundary of the atmosphere have been obtained. We have proposed a technique for the diagnostics of BrC and BC in smoke aerosol particles from the spectral dependence of the imaginary part of the refractive index. At a wavelength of 440 nm, the contributions of BrC and BC to the smokeaerosol absorbing abitity can be comparable in magnitude. In many cases, the absorption spectra of smoke aerosol can be adequately approximated by either power or exponential functions. The presence of BrC in smoke-aerosol particles highly extends the variety of observed absorption spectra in a smoky atmosphere and spectral dependences of single scattering albedo. In the spectral range of 440-1020 nm, the radiative characteristics of smoke aerosol are largely contributed by its fine mode. [ABSTRACT FROM AUTHOR]

General characteristics of methanol (CH3OH) maser emission are summarized. It is shown that methanol maser sources are concentrated in the spiral arms. Most of the methanol maser sources from the Perseus arm are associated with embedded stellar clusters and a considerable portion is situated close to compact HII regions. Almost 1/3 of the Perseus Arm sources lie at the edges of optically identified HII regions which means that massive star formation in the Perseus Arm is to a great extent triggered by local phenomena. A multiline analysis of the methanol masers allows us to determine the physical parameters in the regions of maser formation. Maser modelling shows that class II methanol masers can be pumped by the radiation of the warm dust as well as by free-free emission of a hypercompact region (hcHII) with a turnover frequency exceeding 100 GHz. Methanol masers of both classes can reside in the vicinity of hcHIIs. Modelling shows that periodic changes of maser fluxes can be reproduced by variations of the dust temperature by a few percent which may be caused by variations in the brightness of the central young stellar object reflecting the character of the accretion process. Sensitive observations have shown that the masers with low flux densities can still have considerable amplification factors. The analysis of class I maser surveys allows us to identify four distinct regimes that differ by the series of their brightest lines. [ABSTRACT FROM PUBLISHER]