Conditional Background Level of Aerosol Pollution in Surface Air in Moscow and One of its Suburbs: Seasonal Variations

Abstract

Data from continuous observations of aerosol composition in the surface atmosphere in Moscow (in the city center) and in Moscow oblast (near the city of Zvenigorod) for three years, from the fall of 2019 to the end of 2022, are analyzed. The data were compared with the results of observations at the Moscow network of stations of the State Budgetary Institution Mosecomonitoring. The concept of conditional background aerosol pollution of the near-surface atmosphere in Moscow has been introduced for those days when the daily mean mass concentration of PM₁₀ particles was below the maximum permissible concentration (MPC) (60 μg/m³). The number of such days exceeded 91% in Moscow over three years of observations. Previously, the authors found that all episodes of higher aerosol pollution of urban air (exceeding the MPC) are associated either with the presence of a close local source in the city or with the long-distance transport of combustion aerosols and/or dust to Moscow and its suburbs from other regions. The daily mean concentration of PM_2.5 in the city and the suburb is year-round below the MPC (35 μg/m³). The conditional background aerosol pollution of the surface atmosphere is formed by both natural and anthropogenic sources of aerosols, not only of local, but also of remote origin. Its level and composition implicitly reflect the influence of meteorological parameters on the sources and sinks of aerosols and also the influence of advective transport of aerosol by air masses to and from the city. The results of analysis of seasonal variations in various indicators of aerosol composition in the surface atmosphere under conditional background pollution are presented: the mass concentration of PM₁₀ and PM_2.5 particles and individual chemical elements and the distribution of chemical elements by size of aerosol particles. Similarities and differences between these characteristics in the surface air of the city and the suburb in different seasons are specially emphasized.