Brown Carbon Formation from Nighttime Chemistry of Unsaturated Heterocyclic Volatile Organic Compounds
Brown Carbon Formation from Nighttime Chemistry of Unsaturated Heterocyclic Volatile Organic Compounds
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DOI：
10.1021/acs.estlett.9b00017
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发表时间：
2019-03-01
影响因子：
10.9
通讯作者：
Lin, Ying-Hsuan
中科院分区：
文献类型：
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作者：
Jiang, Huanhuan;Frie, Alexander L.;Lin, Ying-Hsuan
夜间大气处理促进了生物质燃烧羽流中棕色碳气溶胶(BRC)的形成。杂环化合物是一类富含于生物质燃烧烟气中的挥发性有机化合物，可能是BRC的来源。在这里，我们研究了作为BRC来源的三种不饱和杂环化合物(吡咯、呋喃和噻吩基)在硝酸根(NO3)作用下的氧化反应。报道了二次有机气溶胶的375 nm折射率虚部(k(375))、375 nm单次散射反照率(SSA(375))和平均质量吸收系数(<；MAC>；(290-700 nm))。与呋喃和噻吩氧化相比，硝酸氧化吡咯具有最高的SOA产率。吡咯型SOA(k(375)=0.015 0.003，SSA=0.860.01，<；MAC>；(290-700 nm)=3400+/-700 cm(2)g(-1))也比呋喃(<；MAC>；(2 90-70 0 nm)=110 0+/-2 0 0 cm(2)g(-1))和噻吩型SOA(k(375)=0.003 0.002，SSA(375)=0.980.01，(MAC)(2 90-70 0)(Nm)=30 0 0+/-5 0 0 cm(2)g(-1))。与其他SOA系统相比，本研究中报道的MAC高于来自生物前体的MAC，与高NOx人为SOA相似。利用高分辨率质谱学对SOA分子组成的表征表明，不饱和杂环硝基产物或有机硝酸盐可能是BRC中所有三种前驱体的生色团。这些发现揭示了火灾来源的杂环化合物，特别是吡咯，作为BRC的一个合理来源的夜间氧化。
Nighttime atmospheric processing enhances the formation of brown carbon aerosol (BrC) in biomass burning plumes. Heterocyclic compounds, a group of volatile organic compounds (VOCs) abundant in biomass burning smoke, are possible BrC sources. Here, we investigated the nitrate radical (NO3)-initiated oxidation of three unsaturated heterocyclic compounds (pyrrole, furan, and thiophene) as a source of BrC. The imaginary component of the refractive index at 375 nm (k(375)), the single scattering albedo at 375 nm (SSA(375)), and average mass absorption coefficients (< MAC >(290-700 nm)) of the resulting secondary organic aerosol (SOA) are reported. Compared to furan and thiophene, NO3 oxidation of pyrrole has the highest SOA yield. Pyrrole SOA (k(375) = 0.015 0.003, SSA = 0.86 0.01, < MAC >(290-700 nm) = 3400 +/- 700 cm(2) g(-1)) is also more absorbing than furan SOA (< MAC >(290-700 nm) = 1100 +/- 200 cm(2) g(-1)) and thiophene SOA (k(375) = 0.003 0.002, SSA(375) = 0.98 0.01, (MAC)(290-700) (nm) = 3000 +/- 500 cm(2) g(-1)). Compared to other SOA systems, MACs reported in this study are higher than those from biogenic precursors and similar to high-NOx anthropogenic SOA. Characterization of SOA molecular composition using high-resolution mass spectrometric measurements revealed unsaturated heterocyclic nitro products or organonitrates as possible chromophores in BrC from all three precursors. These findings reveal nighttime oxidation of fire-sourced heterocyclic compounds, particularly pyrrole, as a plausible source of BrC.