Assessing formic and acetic acid emissions and chemistry in western U.S. wildfire smoke: implications for atmospheric modeling
Assessing formic and acetic acid emissions and chemistry in western U.S. wildfire smoke: implications for atmospheric modeling
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评估美国西部野火烟雾中的甲酸和乙酸排放和化学成分：对大气模型的影响
DOI：
10.1039/d3ea00098b
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Palm, Brett B.
中科院分区：
文献类型：
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作者：
Permar, Wade;Wielgasz, Catherine;Jin, Lixu;Chen, Xin;Coggon, Matthew M.;Garofalo, Lauren A.;Gkatzelis, Georgios I.;Ketcherside, Damien;Millet, Dylan B.;Palm, Brett B.
甲酸（FA）和乙酸（AA）是大气中最丰富的两种有机酸，通常被大气模型低估。在这里，我们研究了在we - can和FIREX-AQ飞机运动期间采样的生物质燃烧烟雾中的排放，化学和测量不确定性。我们观察到的FA排放比（ERs）和排放因子（EFs）普遍高于文献值的第75个百分位数，与燃料类型或燃烧效率的关系不大。观察到羽流中FA的快速生成（2.7 ppb ppmCO−1 h−1），代表在半天内将总排放的活性有机碳转化为FA的比例高达20%。AA ERs和EFs与文献一致，在羽流老化的<8小时内很少或没有观察到二次生产。使用明确的主化学机制或简化的GEOS-Chem化学的箱形模型无法捕捉到近场观测到的FA和AA趋势，即使将模型的初始VOC浓度提高了三倍。因此，GEOS-Chem化学输运模型低估了美国西部的两种酸，其因子为100亿美元。这可能是由于生物质燃烧烟雾和/或针叶林生物源排放中缺少二级化学。这项工作强调了测量中的不确定性（高达100%），甚至是污染环境中有机酸化学形成的巨大未知数，这两个问题都需要解决，以更好地了解它们的全球预算。
Formic acid (FA) and acetic acid (AA), two of the most abundant organic acids in the atmosphere, are typically underestimated by atmospheric models. Here we investigate their emissions, chemistry, and measurement uncertainties in biomass burning smoke sampled during the WE-CAN and FIREX-AQ aircraft campaigns. Our observed FA emission ratios (ERs) and emission factors (EFs) were generally higher than the 75th percentile of literature values, with little dependence on fuel type or combustion efficiency. Rapid in-plume FA production was observed (2.7 ppb ppmCO−1 h−1), representing up to ∼20% of the total emitted reactive organic carbon being converted to FA within half a day. AA ERs and EFs showed good agreement with the literature, with little or no secondary production observed within <8 hours of plume aging. Observed FA and AA trends in the near-field were not captured by a box model using the explicit Master Chemical Mechanism nor simplified GEOS-Chem chemistry, even after tripling the model's initial VOC concentrations. Consequently, the GEOS-Chem chemical transport model underestimates both acids in the western U.S. by a factor of >4. This is likely due to missing secondary chemistry in biomass burning smoke and/or coniferous forest biogenic emissions. This work highlights uncertainties in measurements (up to 100%) and even large unknowns in the chemical formation of organic acids in polluted environments, both of which need to be addressed to better understand their global budget.