Shakiba Talebian

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.

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.

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.

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.

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.

Brown carbon (BrC) aerosols, primarily emitted from biomass burning events such as wildfires, significantly impact the climate by absorbing sunlight and contributing to atmospheric warming. However, the details of BrC photochemical aging are not fully understood. When exposed to UV radiation, the chemical composition and optical properties of BrC can change, influencing atmospheric radiative forcing. Previous studies suggested that water‐soluble BrC in clouds and fog initially experiences enhanced light absorption due to phenolic monomers forming dimers. However, the identities of dimers responsible for the enhancement have neither been identified nor quantified. This study investigates the direct photolysis of a few key phenolic compounds present in BrC under UVA and UVB radiation. In particular, vanillin was used as a model compound with an aim to identify and quantify divanillin, the dimer of vanillin, and evaluate its role in photo‐enhancement. Using liquid chromatography‐mass spectrometry and UV‐visible spectroscopy, we confirmed the formation of phenolic dimers during photolysis. Quantitative analysis of vanillin revealed that while phenolic homodimers formed under both UVA and UVB conditions, with yields peaking at approximately 10% after 5 min, their contribution to enhanced visible‐range absorption was minor (about 10%). Our observations indicate that not all dimers contribute equally to photo‐enhancement. While divanillin showed negligible absorbance, the demethylated dimer (dimer‐) correlated better with the observed optical changes. This suggests that differences in molecular structure and conjugation, rather than the dimer backbone alone, are critical for absorbance, highlighting the need to distinguish between different dimers and oligomers in atmospheric models.

Quantification of total N-nitrosamines (TONO) is critical for assessing environmental carcinogens. UV-chemiluminescence (UV-CL) shows promise for TONO analysis; however, the data accuracy is limited by matrix interference and the analyte-specific method sensitivity. To overcome these challenges, we designed a new online UV-CL analyzer integrating anion exchange cartridges (AEC) and a homemade nebulizer. The AEC eliminates interference from a wide concentration range of NO₂^-. The nebulizer effectively introduces both volatile and less-volatile nitrosamines, achieving 98.4% photolysis while requiring only 14-53% of the UV dosage used in previous studies. Our analyzer achieved a universal calibration across structurally diverse N-nitrosamines, simplifying quantitative N-nitrosamine measurements. We further demonstrated its application by measuring TONO in authentic tobacco products. Compared to liquid chromatography mass spectrometry (LC-MS), the analyzer obtained consistent kinetic results when monitoring the reaction between NO₂^- and nornicotine, supporting its application in kinetic studies. Moreover, our preliminary analysis of flavored e-juices shows that they could contain up to 0.24 μmol/g of TONO, which could increase further when an environmental level of NO₂^- (6.7 mg/L) is present. Comparing results obtained using the analyzer and LC-MS, known tobacco-specific nitrosamines (TSNAs) account for less than 5.5% of TONO, indicating that most N-nitrosamines in tobacco are unknown. This led to the tentative identification of two new N-nitrosamines: pyridine-methylated N-nitrosoanatabine and pyridine-methylated N-nitrosoanabasine using high-resolution HPLC-MS/MS. Our results supported the feasibility of using the UV-CL analyzer for rapid TONO measurements and highlighted the need to monitor N-nitrosamine contamination in e-juice and tobacco products.