Chemical and physical transformations of organic aerosol from the photo-oxidation of open biomass burning emissions in an environmental chamber
Chemical and physical transformations of organic aerosol from the photo-oxidation of open biomass burning emissions in an environmental chamber
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DOI：
10.5194/acp-11-7669-2011
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发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Robinson, A. L.
中科院分区：
文献类型：
--
作者：
Hennigan, C. J.;Miracolo, M. A.;Robinson, A. L.
利用烟雾箱实验研究了开放式生物质燃烧排放物光氧化过程中有机气溶胶（OA）的化学和物理转化。这些实验是在美国林务局火灾科学实验室进行的，作为米苏拉实验（FLAME III）第三个火灾实验室的一部分。我们调查了北美野火中常见的12种不同燃料的排放量。实验的特点是大气和羽气溶胶和氧化剂浓度;老化时间为3至4.5小时。OA产生，表示为质量增强比（OA与原发性OA（POA）质量的比值），是高度可变的。OA质量增强比范围从2.9在实验中，其中二次OA（SOA）生产几乎三倍的POA浓度到0.7在实验中，其中光氧化导致的OA质量损失30%。平均OA质量增强比为1.7 +/- 0.7（平均值+/- 1 sigma）;因此，平均而言，有大量SOA产生。在每个实验中，OA都被化学转化。即使在OA质量净损失的实验中，OA也随着老化而变得越来越含氧并且挥发性降低，这表明光氧化转化了POA排放。左旋葡聚糖浓度也随着光氧化而显著降低。POA的转换是广泛的，使用左旋葡聚糖作为POA的示踪剂，未反应的POA仅贡献了17%的平均OA质量后，3.5小时的暴露于典型的大气羟基自由基（OH）水平。与OH的非均相反应可以占不到一半的这种转变，这意味着耦合的气体-颗粒分配和反应的半挥发性蒸汽是一个重要的和潜在的主导机制POA处理。总的来说，结果表明，生物质燃烧排放物在大气中受到广泛的化学处理，这些转变的时间尺度很快。
Smog chamber experiments were conducted to investigate the chemical and physical transformations of organic aerosol (OA) during photo-oxidation of open biomass burning emissions. The experiments were carried out at the US Forest Service Fire Science Laboratory as part of the third Fire Lab at Missoula Experiment (FLAME III). We investigated emissions from 12 different fuels commonly burned in North American wildfires. The experiments feature atmospheric and plume aerosol and oxidant concentrations; aging times ranged from 3 to 4.5 h. OA production, expressed as a mass enhancement ratio (ratio of OA to primary OA (POA) mass), was highly variable. OA mass enhancement ratios ranged from 2.9 in experiments where secondary OA (SOA) production nearly tripled the POA concentration to 0.7 in experiments where photo-oxidation resulted in a 30% loss of the OA mass. The campaign-average OA mass enhancement ratio was 1.7 +/- 0.7 (mean +/- 1 sigma); therefore, on average, there was substantial SOA production. In every experiment, the OA was chemically transformed. Even in experiments with net loss of OA mass, the OA became increasingly oxygenated and less volatile with aging, indicating that photo-oxidation transformed the POA emissions. Levoglucosan concentrations were also substantially reduced with photo-oxidation. The transformations of POA were extensive; using levoglucosan as a tracer for POA, unreacted POA only contributed 17% of the campaign-average OA mass after 3.5 h of exposure to typical atmospheric hydroxyl radical (OH) levels. Heterogeneous reactions with OH could account for less than half of this transformation, implying that the coupled gas-particle partitioning and reaction of semi-volatile vapors is an important and potentially dominant mechanism for POA processing. Overall, the results illustrate that biomass burning emissions are subject to extensive chemical processing in the atmosphere, and the timescale for these transformations is rapid.