新鲜和老化生物质燃烧气溶胶中有机成分的分子特征。
Molecular characteristics of organic compositions in fresh and aged biomass burning aerosols.
机构信息
Key Lab of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
Key Lab of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
出版信息
Sci Total Environ. 2020 Nov 1;741:140247. doi: 10.1016/j.scitotenv.2020.140247. Epub 2020 Jun 16.
Biomass burning (BB) is the most important source of primary organic aerosols (OA) in the atmosphere that has significant impact on local/regional air quality and human health. However, few studies paid attention to the evolution of molecular characteristics of BB OA in the atmospheric aging processes. In this study, both fresh and aged PM aerosols from burning of rice, maize, and wheat straws were collected from a combined system of combustion chamber and oxidation flow reactor, and were analyzed for >100 organic species. The emission factors (EFs) of anhydrosugars and some fatty acids showed slight variations between fresh and aged samples, indicating that these compounds are relatively stable. However, the EFs of n-alkanes, fatty alcohols, and parent-PAHs decreased 8-57% from fresh to aged samples, suggesting that they can undergo further oxidation to form other organic materials in the atmosphere. Phthalic acids, nitrophenols and isoprene-derived products were mainly secondarily formed by aging processes. Thus their EFs increased by 2-23 times from fresh to aged samples. Levoglucosan was the most abundant individual organic tracer, and its EF varied slightly between fresh and aged samples, proving its indicative role on BB emission. Moreover, the ratio of vanillic acid to levoglucosan and p-hydroxybenzoic acid to levoglucosan increased 2-13 times from fresh to aged samples. Therefore they can be used to investigate the impact of aging processes on BB aerosols in the atmosphere. RO + HO pathway derived 2-methyltetrols (2-MTs) predominated the EFs of isoprene-derived products (SOA) in the fresh samples. However, RO + NO pathway derived 2-methylglyceric acid (2-MGA) increased by >30 times and became comparable with 2-MTs in aged particles. The ratio of 2-MGA/2-MTs increased from 0.06-0.27 in fresh samples to 0.94-1.18 in aged samples, because the high loading of NO in BB smoke enhanced the formation of SOA through RO + NO reactions.
生物质燃烧（BB）是大气中初级有机气溶胶（OA）的最重要来源，对当地/区域空气质量和人类健康有重大影响。然而，很少有研究关注 BB OA 在大气老化过程中分子特征的演变。在这项研究中，从燃烧水稻、玉米和麦秸的燃烧室和氧化流动反应器的组合系统中收集了新鲜和老化的 PM 气溶胶，并对 >100 种有机物质进行了分析。无水糖和一些脂肪酸的排放因子（EF）在新鲜和老化样品之间略有变化，表明这些化合物相对稳定。然而，正构烷烃、脂肪醇和母体多环芳烃的 EF 从新鲜到老化样品降低了 8-57%，表明它们可以在大气中进一步氧化形成其他有机物质。邻苯二甲酸、硝基酚和异戊二烯衍生产物主要是通过老化过程形成的。因此，它们的 EF 从新鲜到老化样品增加了 2-23 倍。左旋葡聚糖是最丰富的单个有机示踪剂，其 EF 在新鲜和老化样品之间变化不大，证明了它在 BB 排放中的指示作用。此外，香草酸与左旋葡聚糖和对羟基苯甲酸与左旋葡聚糖的比值从新鲜到老化样品增加了 2-13 倍。因此，它们可以用来研究老化过程对大气中 BB 气溶胶的影响。在新鲜样品中，RO+HO 途径衍生的 2-甲基四醇（2-MTs）主导了异戊二烯衍生产物（SOA）的 EF。然而，RO+NO 途径衍生的 2-甲基甘油酸（2-MGA）增加了 >30 倍，在老化颗粒中与 2-MTs 相当。2-MGA/2-MTs 的比值从新鲜样品中的 0.06-0.27 增加到老化样品中的 0.94-1.18，因为 BB 烟雾中高浓度的 NO 增强了通过 RO+NO 反应形成 SOA。
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