We present emission measurements of volatile organic compounds (VOCs) for western U.S. wildland fires made on the NSF/NCAR C-130 research aircraft during the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) field campaign in summer 2018. VOCs were measured with complementary instruments onboard the C-130, including a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) and two gas chromatography (GC)-based methods. Agreement within combined instrument uncertainties (<60%) was observed for most co-measured VOCs. GC-based measurements speciated the isomeric contributions to selected PTR-ToF-MS ion masses and generally showed little fire-to-fire variation. We report emission ratios (ERs) and emission factors (EFs) for 161 VOCs measured in 31 near-fire smoke plume transects of 24 specific individual fires sampled in the afternoon when burning conditions are typically most active. Modified combustion efficiency (MCE) ranged from 0.85 to 0.94. The measured campaign-average total VOC EF was 26.1 ± 6.9 g kg⁻¹, approximately 67% of which is accounted for by oxygenated VOCs. The 10 most abundantly emitted species contributed more than half of the total measured VOC mass. We found that MCE alone explained nearly 70% of the observed variance for total measured VOC emissions (r² = 0.67) and >50% for 57 individual VOC EFs representing more than half the organic carbon mass. Finally, we found little fire-to-fire variability for the mass fraction contributions of individual species to the total measured VOC emissions, suggesting that a single speciation profile can describe VOC emissions for the wildfires in coniferous ecosystems sampled during WE-CAN.

中文翻译：

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基于 WE-CAN 飞机测量结果的美国西部野火中痕量有机气体的排放

在夏季的云化学、气溶胶吸收和氮 (WE-CAN) 野外活动西部野火实验期间，我们展示了美国西部野火的挥发性有机化合物 (VOC) 排放测量值，该测量是在 NSF/NCAR C-130 研究飞机上进行的2018. 使用 C-130 上的补充仪器测量 VOC，包括质子转移反应飞行时间质谱仪 (PTR-ToF-MS) 和两种基于气相色谱 (GC) 的方法。对于大多数共同测量的 VOC，观察到组合仪器不确定度 (<60%) 内的一致性。基于 GC 的测量指定了对选定 PTR-ToF-MS 离子质量的异构贡献，并且通常显示出很少的火到火变化。我们报告了 161 种 VOC 的排放比 (ER) 和排放因子 (EF)，这些 VOC 在燃烧条件通常最活跃的下午采样的 24 场特定火灾的 31 次近火烟羽样带中测量。修正燃烧效率 (MCE) 范围为 0.85 至 0.94。测得的运动平均总 VOC EF 为 26.1 ± 6.9 g kg^-1，其中约 67% 为含氧 VOC。排放量最大的 10 种物质占测得的 VOC 总质量的一半以上。我们发现仅 MCE 就解释了近 70% 的观测到的总测量 VOC 排放量（r ²  = 0.67）的方差，而对于代表超过一半有机碳质量的 57 个单独的 VOC EF ，其方差> 50%。最后，我们发现单个物种的质量分数对总测量 VOC 排放量的贡献几乎没有火灾与火灾之间的变异性，这表明单个物种形成概况可以描述 WE-CAN 期间采样的针叶生态系统中野火的 VOC 排放量。