Near-Surface Concentration of CH4, CO2, CO, and δ13C-CH4 in the Air Based on the Observations at the Station of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, in Moscow

Results of the analysis of interannual, seasonal, and diurnal variations in the ratios of the mixture of CH4, CO2, CO, benzene, and delta C-13-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 delta C-13-CH4 values (-50 to -60 parts per thousand ). 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/CO = 0.56-0.75 ppm/ppm, CO2/benzene = 77-93 ppm/ppb, CO2/CO = 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.

Automated summary

This study presents the analysis of the ratios of CH4, CO2, CO, benzene, and delta C-13-CH4 in the surface air of Moscow, based on measurements at the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. The results show the interannual, seasonal, and diurnal variations of these ratios, highlighting the contribution of motor transport and thermal power plants as the main sources of urban pollution emissions.