Abstract
Measurements of CO and 15 volatile organic compounds (VOCs) at the IAP-RAS (A.M. Obukhov Institute of Atmospheric Physics) site located in the center of Moscow were analyzed. Acetaldehyde, ethanol, 1.3-butadiene, isoprene, toluene and C-8 aromatics were established to be the main ozone precursors in the observed area, providing up to 82% of the total ozone formation potential of the VOCs measured. Diurnal and seasonal variations of the compounds are discussed. The concentrations of anthropogenic VOCs (acetaldehyde, benzene, 1.3-butadiene, toluene, and C-8 aromatics) did not exceed their maximum permissible levels, reaching their maxima in summer and autumn in the morning and evening hours. Biogenic ethanol and isoprene were the highest in summer midday but their concentrations were low enough (up to 4 and 0.4 ppbv, respectively) due to small vegetation area around the site. Emission ratios (ERs) for the main ozone precursors—acetaldehyde, ethanol, 1.3-butadiene, isoprene, toluene, and C-8 aromatics—were estimated from two-sided linear regression fits using benzene and CO as tracers for anthropogenic emissions, with spatial and temporal filters being applied to account for the influence of chemistry and local emission sources. The best estimates of ERs were obtained using benzene as a reference species. Anthropogenic fractions of VOCs (AFs) were then estimated. As expected, acetaldehyde, toluene, 1.3-butadiene, and C8aromatics were entirely anthropogenic and emitted mainly from urban vehicle exhausts throughout the day, both in summer and in winter. AFs of isoprene and ethanol did not exceed 30% and 50% in summer, respectively, during both daytime and nighttime hours. In winter, the anthropogenic fractions of isoprene and ethanol were slightly higher (up to 35% and 60%, respectively).
Highlights
Atmospheric volatile organic compounds (VOCs) play an important role in determining the air quality and driving climate change [1], including the formation of ozone (O3) and secondary organic aerosols (SOA)
The results provide the most complete estimates of Moscow megapolis emissions and VOC composition at present, providing a basis for future comparisons with other urban environments worldwide
We focus on the above VOCs in the subsequent discussion, as their near-surface abundance is indicative of the strength of primary sources of atmospheric contamination that are most important for the urban ozone photochemistry in Moscow
Summary
Atmospheric volatile organic compounds (VOCs) play an important role in determining the air quality and driving climate change [1], including the formation of ozone (O3) and secondary organic aerosols (SOA). As was shown earlier by [3] Berezina et al (2020), the greatest impact on ozone generation in Moscow city (up to 136 μg/m3 in high-ozone episodes) is due to acetaldehyde, ethanol, 1.3-butadiene, acetic acid, C8 aromatics, toluene and isoprene emissions These VOCs are known to have primary and secondary sources in the urban atmosphere. The second reason is the high spatial and temporal variability in VOC emissions in urban environments, which complicates estimates of the strength of the role of pollutant sources of individual VOCs in ozone chemistry based on direct measurements of air chemical composition. We used the mixing ratios of either benzene or CO as reference quantities for anthropogenic emissions to evaluate the ERs of the most ozone-producing VOCs and to identify their main sources in Moscow based on direct surface measurements of VOCs in 2019–2020. The results provide the most complete estimates of Moscow megapolis emissions and VOC composition at present, providing a basis for future comparisons with other urban environments worldwide
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
