Comprehensive mass spectrometric analysis of unprecedented high levels of carbonaceous aerosol particles long-range transported from wildfires in the Siberian Arctic

Abstract. 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. Particulate matter (PM) of aged wildfire plumes with origin from Yakutia in August 2021 was collected in Nadym city and on Bely Island (both northwest Siberia). A comprehensive analysis of the chemical composition of aerosol particles 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 by ultra-high resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In Nadym city, concentrations of organic carbon (OC) and elemental carbon (EC) were peaking at 100 µg m^-3 and 40 µg m^-3, respectively, associated with Angström Absorption Exponents for 405 and 808 nm (AAE_405/808) between 1.5 and 3.3. The weekly average on Bely Island peaked at 8.9 µg m^-3 of OC and 0.3 µg m^-3 of EC, and AAE_405/808 close to unity. Particularly, ambient aerosol in Nadym city had a distinct biomass burning profile with pyrolysis products from carbohydrates, such as cellulose and hemi-cellulose, as well as lignin and resinoic acids. However, temporarily higher concentrations of 5- and 6-ring polycyclic aromatic hydrocarbons (PAHs), different from the PAH signature of biomass burning, suggests a contribution of regional gas flaring. FT-ICR MS with electrospray ionization (ESI) revealed a complex mixture of highly functionalized compounds, containing up to twenty oxygen atoms, as well as nitrogen- and sulfur-containing moieties. Concentrations of biomass burning markers on Bely Island were substantially lower than in Nadym city, flanked by appearance of unique compounds with higher oxygen content, higher molecular weight and lower aromaticity. Back trajectory analysis and satellite-derived aerosol optical depth suggested long-range transport of aerosol from the center of a Yakutian wildfire plume to Nadym city and the plume periphery to Bely Island. Owing to lower aerosol concentration in the plume periphery than in its center, it is demonstrated how dilution affects the chemical plume composition during atmospheric aging.