Characterization of trace gas emissions from controlled laboratory burning of Canadian boreal forest fuels

Abstract. Although boreal wildfires are a major global source of trace gases, their emissions remain poorly characterized. To address this gap, controlled burns of Canadian Boreal surface and ground fuels were conducted during the Biomass Burning Canada (BBCan) Campaign. Emission factors (EF) for 46 volatile organic compounds (VOC) were determined using iodide chemical ionization mass spectrometry (I-CIMS) and Vocus proton transfer reaction mass spectrometry (Vocus PTR-MS). Total non-methane organic compound (NMOC) emissions, which were measured separately, were found to account for 1–13 % of total emitted gas-phase carbon (i.e., CO₂, CO, CH₄, NMOC), with total quantified VOCs (ΣVOCs) accounting for 13–34 % of that fraction. The dominant compounds contributing to the measured ΣVOCs include oxygenates and organic reactive nitrogen (Nr) species. Boreal peat fuels, which are prone to residual smoldering combustion, produced significantly higher total NMOC, total Nr, and individual VOC emissions than the other fuels. In contrast, boreal mulch, which burned very efficiently, produced low emissions. Combustion efficiency was observed to have a strong impact on total and individual VOC emissions, but VOC emission profiles were also dependent on fuel type and moisture content. The findings indicate that the EFs currently used to speciate NMOC emission may not adequately capture emissions from smoldering boreal peat fires. Study results provide the first comprehensive VOC EF for fresh emissions for a range of Canadian boreal surface and ground fuels, which can be used to improve emission inventories and enhance predictions of wildfire smoke impacts on air quality, climate, and health.