ИСТИНА

Annual wildfires in Siberia generate large amounts of aerosols, which may be transported over long distances and pose a threat to the sensitive ecosystem of the Arctic. Filter samples of aged wildfire plumes, originating in Central Yakutia in August 2021, as revealed from back trajectory analysis, were collected in Nadym city and on Bely Island (Western Siberia). A comprehensive analysis of the chemical aerosol composition was conducted by multi-wavelength thermal-optical carbon analyzer (TOCA) coupled to resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) as well as ultra-high resolution Fourier-Transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In Nadym, concentrations of organic carbon (OC) and elemental carbon (EC) were peaking at 100 µg m-3 and 40 µg m-3 , respectively, associated with an Angström Absorption Exponent for 405 and808 nm (AAE405/808) of 2.1. A maximum week average on Bely Island resulted in 8.9 µg m-3 of OC and 0.3 µg m-3 of EC, , and an AAE405/808 up to 1.2. Particularly aerosol in Nadym had a distinct biomass burning profile with pyrolysis products from carbohydrates, such as cellulose and hemi-cellulose, as well as lignin and resinoic acids.The contribution of regional gas flaring to the aerosol load could be derived from the changing pattern of polycyclic aromatic hydrocarbons (PAH) with higher concentrations of 5- and 6-ring PAH. FT-ICR MS reveals a complex mixture of highly functionalized compounds, containing up to twenty oxygen atoms, as well as nitrogen and sulfur- containing moieties, as the resultof atmospheric aging for both samples. Biomass burning markers on Bely Island were substantial lower than in Nadym, flanked by appearance of unique compounds with higher oxygen content, higher molecular weight and lower aromaticity, which is related to different aging during long-range transport of the plume periphery and center