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Contributions of anthropogenic and wetland methane emissions in Northern Eurasia (>40° N) and Russia into the near-surface CH4 abundance are quantified using GEOS-chem global chemical transport model at ZOTTO, Teriberka, and Tiksi measurement sites. Numerical results agree well with the proposed semianalytical solution, in which the total contribution (atmospheric response) in the CH4 level at a given site is decomposed into direct (synoptic) and global terms. On an advection timescale corresponding to a synoptic time interval, the annual average direct contribution of Russian anthropogenic emissions into the CH4 mixing ratio measured at ZOTTO (38.6 ppbv) is more than twice as large as that for Western Europe sources (17.7 ppbv). For the Arctic sites, the anthropogenic inputs from Russian and European sources are roughly similar (19.5 and 12.4 ppbv, respectively). The input from continental sources into near-surface methane abundance and its annual variations at the Arctic sites are generally lower compared to those at the ZOTTO site due to larger transport times from upstream CH4 source regions. Model-based atmospheric responses in methane levels at the Teriberka and Tiksi sites to continental CH4 sources are found to be very close owing to the relatively homogeneous (circumpolar) spatial distributions of the anthropogenic and biogenic signals at high latitudes. [ABSTRACT FROM AUTHOR] more...

Results of the analysis of interannual, seasonal, and diurnal variations in the ratios of the mixture of CH4, CO2, CO, benzene, and δ13C–CH4</subscript> 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] more...

The rates of ozone production (P) and sink (L) and total peroxide (OX) content are assessed with the use of the photostationary state approach from measurements of ozone (O3) and nitrogen oxides (NO and NO2) at the Zotino Tall Tower Observatory (ZOTTO), central Siberia, in 2007–2014. Mean daily cycles of the above quantities for May–September cloud-free days peak at 6 ppb/hour (P), 1.4 ppb/hour (L), and 115 ppb ([OX]) between 11:00 and 15:00 LT. The linear dependence of P on [NOx] is derived in the range of measured NOx mixing ratios from 0.2–0.8 ppb, suggesting for NOx-limiting conditions of ozone production, with the slope rate P(O3)/[NOx] estimated at 13 (ppb/h)/ppb. The estimated high OX levels along with the condition P ⪢ L manifest for high rates of the in situ oxidation of biogenic volatile organic compounds and photochemical ozone generation. The surface air layer can be treated as an ozone source for the atmospheric boundary layer over remote areas of Siberia at NOx concentrations corresponding to conditions of both regionally background air and weakly polluted air. The obtained estimates indicate the significant role of regional NOx emissions in the ground-level ozone budget and necessity of taking this factor into account when forecasting ecological risks in Siberian regions that are commonly considered pollution-free. [ABSTRACT FROM AUTHOR] more...

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] more...

Seasonal variations of the near‐surface NOX (= NO + NO2) and ozone (O3) mixing ratios at Zotino Tall Tower (ZOTTO), a remote site in central Siberia, are described for years 2007–2014. Conditional probability function analysis and back trajectories are used to determine the origins of clean (continental baseline, CB) and regional emissions‐influenced air. High NOX levels at the site are observed for air from industrial regions of western Siberia and Ural Mountains, whereas CB air originates from remote areas of North Eurasia within 55°–70°N. The estimated annual means of daytime O3 and NOX mixing ratios for CB air are 27.0 and 0.44 ppbv, correspondingly, versus the similar quantities of 27.9 and 0.79 ppbv for all data. Monthly ozone for CB air shows a distinct maximum in April, as is the case for Northern Hemisphere midlatitude baseline (NHMLB) air at the European inflow boundary according to the surface ozone data for Mace Head and Norwegian monitoring sites, and a minimum in late summer–early autumn reflecting a weak continental‐scale ozone production from biogenic sources of ozone precursors and wildfire emissions throughout the warm season. During spring and early summer under hot weather conditions, regional anthropogenic and wildfire emissions are an important source for ozone in the continental boundary layer over southern and central Siberia, resulting in surface ozone levels compared to or larger than those observed in NHMLB air. Throughout the remaining part of year, the central North Eurasia represents a sink for tropospheric ozone on a hemispheric scale. Key Points: Seasonal variations of NOX and O3 at ZOTTO in Siberia show a signature of weakly polluted air due to the regional pollutionOrigins of clean and polluted air for the site are identified; seasonal cycle of the baseline ozone for central North Eurasia is estimatedIn spring‐summer, anthropogenic and fire emissions in Siberia provide a net source for tropospheric ozone in the NH midlatitudes [ABSTRACT FROM AUTHOR] more...

The results of an intensive complex experiment carried out from March 25 to May 3, 2020, to study the composition and time variability of urban aerosol in the atmosphere in the center of Moscow include data on daily mean concentrations of both РМ10 and РМ2.5 particles and 65 chemical elements. The concentrations of all components did not exceed the maximum permissible concentration (MPC) for residential areas. The exception was increased РМ10 concentrations recorded on March 27–29, when air masses from neighboring regions with biomass fires arrived in the city. The coefficients of correlation between values of the concentrations and enrichment factors of the elements confirmed the anthropogenic/local origin of some heavy metals (Cd, Sb, Pb, Se, Th) and the terrigenous/global origin of elements such as Mn, Mg, Zn, Co, Fe, Al, and Cr. The elements S, P, K, Na, Ca, Ni, Cu, Mo, Sn, W, Bi, and U, for which no significant correlation between their concentrations and enrichment factors has been found, apparently, have a mixed origin from both natural and anthropogenic sources competing with each other from day to day. The first studies of the weekly cycle of the relative elemental composition of surface aerosol in Moscow have shown the leading role of meteorological conditions (in particular, air pressure and humidity) in variations of aerosol pollution levels. [ABSTRACT FROM AUTHOR] more...

We use a regional chemistry transport model (Weather Research and Forecasting model coupled with chemistry, WRF-Chem) in conjunction with surface observations of tropospheric ozone and Ozone Monitoring Instrument (OMI) satellite retrievals of tropospheric column NO 2 to evaluate processes controlling the regional distribution of tropospheric ozone over western Siberia for late spring and summer in 2011. This region hosts a range of anthropogenic and natural ozone precursor sources, and it serves as a gateway for near-surface transport of Eurasian pollution to the Arctic. However, there is a severe lack of in situ observations to constrain tropospheric ozone sources and sinks in the region. We show widespread negative bias in WRF-Chem tropospheric column NO 2 when compared to OMI satellite observations from May–August, which is reduced when using ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) v5a emissions (fractional mean bias (FMB) = - 0.82 to - 0.73) compared with the EDGAR (Emissions Database for Global Atmospheric Research)-HTAP (Hemispheric Transport of Air Pollution) v2.2 emissions data (FMB = - 0.80 to - 0.70). Despite the large negative bias, the spatial correlations between model and observed NO 2 columns suggest that the spatial pattern of NO x sources in the region is well represented. Scaling transport and energy emissions in the ECLIPSE v5a inventory by a factor of 2 reduces column NO 2 bias (FMB = - 0.66 to - 0.35), but with overestimates in some urban regions and little change to a persistent underestimate in background regions. Based on the scaled ECLIPSE v5a emissions, we assess the influence of the two dominant anthropogenic emission sectors (transport and energy) and vegetation fires on surface NO x and ozone over Siberia and the Russian Arctic. Our results suggest regional ozone is more sensitive to anthropogenic emissions, particularly from the transport sector, and the contribution from fire emissions maximises in June and is largely confined to latitudes south of 60 ∘ N. Ozone dry deposition fluxes from the model simulations show that the dominant ozone dry deposition sink in the region is to forest vegetation, averaging 8.0 Tg of ozone per month, peaking at 10.3 Tg of ozone deposition during June. The impact of fires on ozone dry deposition within the domain is small compared to anthropogenic emissions and is negligible north of 60 ∘ N. Overall, our results suggest that surface ozone in the region is controlled by an interplay between seasonality in atmospheric transport patterns, vegetation dry deposition, and a dominance of transport and energy sector emissions. [ABSTRACT FROM AUTHOR] more...