Investigating the Presence of Biomass Burning Events at Ny-Å Lesund: Optical and Chemical Insights from Summer-Fall 2019

Summer 2019 is remembered as one of the most intense biomass burning (BB) seasons on record for the Northern Hemisphere. During the MOSAiC expedition, a smoke-dominated layer was identified in the upper troposphere over the North Pole region. The origin of this layer remains unclear, and no evidence has been found to indicate the intrusion of such particles into the Arctic Boundary Layer. The main aim of this work was to evaluate if biomass burning events in the summer 2019 were detectable at Gruvebadet Atmospheric Laboratory, close to Ny-Å lesund (Svalbard Islands) during the second half of 2019. This paper proposes an innovative approach to discriminate biomass burning events based on optical measurements combined with chemical analysis and air mass back-trajectories. Monthly background values of optical coefficients were defined using multi-annual (2018-2021) statistics and twelve possible events were identified. Source apportionment through positive matrix factorization (PMF) identified that the biomass burning factor by PMF accounted for only 2% of the total investigated concentration. The specific biomass burning tracers such as levoglucosan and phenolic compounds were compared with optical measurements and with the PMF results. Air mass trajectory analysis revealed that the early summer fires detected at Ny-Å lesund originated mainly from North America, as also confirmed by the presence of BB factor of PMF, levoglucosan and also vanillic species (softwood combustion tracers). In contrast, the chemical composition and air masses analysis of the highest peak detected in early December suggested residential heating as plausible source, further amplified by the onset of the harsh winter season and the expansion of the polar vortex towards mid-latitudes.