ИСТИНА

Current changes in global climate lead to frequent occurrence of extreme meteorological events, also in high populated regions. Summer 2010 brought an unusual heat into Eastern Europe; starting since 6 August 2010 Moscow megacity was covered with thick smoke of unusually high PM10 and BC concentrations, considerably affected by huge forest and peat fires around megacity (Popovicheva et al., 2014). From March until late summer in 2014, the Tver region, north of the Moscow city, was considerably affected by long-lasting peat bog fires(Popovicheva et al., 2019). Last summer of 2022 wildfires again covered a significant area of Ryazan forests and destroyed the Oksky Biosphere Reserve. The aim of the study is to assess the specific features of biomass burning (BB) aged in the urban atmosphere of Moscow megacity following the transport of smoke plumes from Ryazan wildfires in August 2022. Sampling campaign was performed at the Aerosol Complex of Moscow State University at southwest of Moscow, classified as urban background site, from April to September 2022. Chemical, physical, and spectrally-resolved optical properties of ambient aerosols were analyzed by an extensive suite of instrumentation. CASS was used for high-time-resolution measurements of organic carbon (OC), black carbon (BC), and spectral dependence of absorption coefficient. Source - specific BC components (BCff and BCbb) as well as BB contribution to BC (BB%) were determined by aethalometer model. PM10 and PM2.5 mass concentrations were measured by TEOM 1400a. 24hr PM10 samples were analysed for functionalities by FTIR and morphology by SEM/EDX. According to official info, on August 26 the total area covered by forest fires in the Ryazan region has grown to 17,741.99 hectares. Fire-related days from 10 to 31 August were clearly separated from by twice on average increase of PM10 and PM2.5, 2.3 and 1.8 times increase of OC and BC. Smoke plumes affected an urban site in Moscow, with ambient PM10 mass loadings reaching up to 86 µg/ m3 and OC up to 16 µg/ m3 on 27 August. With the transport of air masses from the Ryazan region to Moscow , the OC/EC ratio and AAE reached peak values of 4.05 and 1.3, respectively. When BB% served as a marker of the impact of biomass burning, approaching a maximum 49% on 21.08.2022. BCbb component showed unprecedented event of 2.3 µg/m3 BCff on 1.2 µg/m3. ( Fig.1), thus demonstrating huge impact of Ryazan wildfires on pollution in large megacity exceeding traffic. Aliphatic, aromatic, carbonyl, and carboxylate functionalities in were enriched by nitro compounds, Organic functionalities of Moscow smoke aerosols were hydroxyl, aliphatic, aromatic, acid and non-acid carbonyl, and nitro compound groups, almost all of them indicate wildfires around city as the source of smoke The mixture of carbonaceous particles and dust revealed multicomponent structure of Moscow smoke aerosols, pointing the difference with non-smoke ambient aerosols. The abundance of group containing only carbonaceous particles approached 10 % of total aerosol concentration during fire-related days. Fly ash groups contained calcium sulfates and carbonates from soil entrainment by hot air convection. Spectral absorbance features showed characteristics during fire and non-fire related days, confirming the potential effect of transported peat smoke on air quality in megacities. and brown carbon (BrC) was identified by a high Absorption Angstrom Exponent (AAE) of 4.1