Quantification of organic aerosol and brown carbon evolution in fresh wildfire plumes
Quantification of organic aerosol and brown carbon evolution in fresh wildfire plumes
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DOI：
10.1073/pnas.2012218117
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发表时间：
2020-11-24
影响因子：
11.1
通讯作者：
Thornton, Joel A.
中科院分区：
文献类型：
--
作者：
Palm, Brett B.;Peng, Qiaoyun;Thornton, Joel A.
野火羽流中有机气溶胶（OA）和棕色碳（BrC）的演变，包括主要与次要来源的相对贡献，一直是不确定的，部分原因是对烟雾羽流的前体排放和化学环境的了解有限。我们在2018年7月至8月对美国西部野火烟雾中的一系列反应性痕量气体，颗粒组成和光学特性进行了空中测量。我们使用这些观测结果来量化野火羽流中生物质燃烧OA（BBPOA与BBSOA）和BrC的主要与次要来源。当一个白天的野火羽稀释了5至10倍，我们估计，高达三分之一的主要OA蒸发，随后反应形成BBSOA与近单位产量。测量的BBSOA前体的反应仅占总BBSOA源的13 +/- 3%，其余部分由蒸发的BBPOA组成。我们发现，酚类化合物的氧化贡献了大部分的BBSOA从排放的蒸汽。据估计，相应的颗粒硝基酚类化合物解释了在烟羽演化的前几个小时内测量的405 nm处的平均BrC光吸收（BrC Abs 405）的29 +/-15%，尽管仅占平均OA质量的4 +/-2%。这些测量提供了定量限制的作用，稀释驱动的OA和随后的自由基驱动的氧化的生物质燃烧OA和溴化碳的命运在白天野火羽流的蒸发，并指出需要了解如何处理夜间排放的不同。
The evolution of organic aerosol (OA) and brown carbon (BrC) in wildfire plumes, including the relative contributions of primary versus secondary sources, has been uncertain in part because of limited knowledge of the precursor emissions and the chemical environment of smoke plumes. We made airborne measurements of a suite of reactive trace gases, particle composition, and optical properties in fresh western US wildfire smoke in July through August 2018. We use these observations to quantify primary versus secondary sources of biomass-burning OA (BBPOA versus BBSOA) and BrC in wildfire plumes. When a daytime wildfire plume dilutes by a factor of 5 to 10, we estimate that up to onethird of the primary OA has evaporated and subsequently reacted to form BBSOA with near unit yield. The reactions of measured BBSOA precursors contribute only 13 +/- 3% of the total BBSOA source, with evaporated BBPOA comprising the rest. We find that oxidation of phenolic compounds contributes the majority of BBSOA from emitted vapors. The corresponding particulate nitro phenolic compounds are estimated to explain 29 +/- 15% of average BrC light absorption at 405 nm (BrC Abs405) measured in the first few hours of plume evolution, despite accounting for just 4 +/- 2% of average OA mass. These measurements provide quantitative constraints on the role of dilution-driven evaporation of OA and subsequent radical-driven oxidation on the fate of biomass-burning OA and BrC in daytime wildfire plumes and point to the need to understand how processing of nighttime emissions differs.