Near-Surface Air Content of CH₄, СО₂, СО and δ¹³C–СH₄ in Moscow According to <i>In Situ</i> Observations

Abstract

Near-surface observations of air mixing ratios of CH4, CO2, CO, benzene, and δ13C–СH4 at the IAP-RAS site in Moscow for years 2018–2020 are analyzed to describe typical interannual, seasonal, and diurnal variations. The highest mixing ratios of CH4, CO2, and CO (above 2.2, 430, and 0.2 ppmv, respectively) are mostly observed in winter as a result of the seasonal maxima in the emissions of these gases from motor transport and energy sectors and the slow removal of the emissions from the near-surface air due to suppressed turbulent vertical mixing in the cold season. The highest impact of local and distant microbial emissions on the CН4 mixing ratios is observed in summer, as follows from the low δ13C–СH4 values from –50 to –60‰. The highest increase in the mixing ratios of all the measured species is associated with air transport from the industrial area located at the east – southeast from the site. The estimated emission ratios CH4/benzene = = 0.52–0.54 ppmv/ppbv, СH4/СО = 0.56–0.75 ppmv/ppmv, СО2/benzene = 77–93 ppmv/ppbv, СО2/СО = = 81–131 ppmv/ppmv, СО/benzene = 0.65–1.11 ppmv/ppbv show the prevailing contribution of emissions from motor transport and energy sectors to the content of trace gases in the near-surface air in Moscow and are consistent with other similar estimates published on the basis of observations in large cities.