Аннотация:Wildfires are an important source of particulate matter in the atmosphere and have a significant impact on the regional atmospheric environment through atmospheric transportation. In this study, PM10 samples were collected at Moscow urban background from June to September 2022, covered the periods of wildfires occurred in the Ryazan forest, 200 km from the city. Mass concentrations of carbonaceous components (organic carbon, OC, and elemental carbon, EC) and water soluble inorganic ions (WSlls) were analyzed to assess the impact of wildfires on the PM10 composition. Based on backward air mass trajectories and fire spot maps analysis, the two pollution events with significantly increased PM10 concentrations (Plume 1 and Plume 2) that occurred in August were identified. During Plume 1 and Plume 2, averaged PM10 were 44.1±7.2 and 71.0±19.2 μg/m3, respectively, 1.9 and 3.0 times higher than during urban background period, nighttime PM10 concentrations were higher than daytime. SOC concentrations increased by 2.0 and 4.8 times, respectively, compared to urban background (3.9±1.9 μg/m3). OC and EC concentrations (Plume 1: 18.8±7.0 and 3.9±1.2 μg/m3; Plume 2: 32.5±15.1 and 5.4±2.4 μg/m3) were significantly higher than those during urban background period (7.7±2.8 and 2.1±1.0 μg/m3). Proportion of organic matter (OM) in PM10 and SOC in OC increased to 68.3% and 73.2% and up to more than 60%. The influence of the transportation of wildfire plumes increased the proportion of OM, especially SOC. The total concentrations of WSlls during Plume 1 and Plume 2 increased by 1.6 and 4.2 times compared to urban background (1.5±0.9 μg/m3), and the proportion of secondary inorganic ions (SNA) in WSlls also increased. Under plumes impact, significant correlations between SNA and K+ were found, and NO3–/SO42– were less than 1, different from urban background (NO3–/SO42–>1), indicating that SNA contributed by wildfire smoke. By comparison of nitrogen oxidation (NOR) and sulfur oxidation (SOR) rates, it indicated the promotion of the conversions of SO2 and NO2 to SO42– and NO3– as a result of wildfire smoke plumes transportation to the megacity, especially the conversion of SO2 at night.
