Biomass-burning-derived particles from a wide variety of fuels: Part 2: Effects of photochemical aging on particle optical and chemical properties
Biomass-burning-derived particles from a wide variety of fuels: Part 2: Effects of photochemical aging on particle optical and chemical properties
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DOI：
10.5194/acp-2020-137
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发表时间：
2020
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影响因子：
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通讯作者：
C. Cappa;C. Lim;D. H. Hagan;M. Coggon;A. Koss;K. Sekimoto;J. D. de Gouw;T. Onasch;C. Warneke;J. Kroll
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作者：
C. Cappa;C. Lim;D. H. Hagan;M. Coggon;A. Koss;K. Sekimoto;J. D. de Gouw;T. Onasch;C. Warneke;J. Kroll
生物质燃烧产生的烟雾中的颗粒物对全球气候和城市空气质量有很大影响。对于粒子的光学性质--尤其是黑碳(BC)和棕碳(BRC)的贡献--如何随着烟雾的光化学老化而演变的了解有限。我们分析了各种生物质燃料燃烧产生的颗粒的光学性质和化学成分的演变，这些燃料主要来自美国西部。烟雾在反应室内进行光化学老化，时间跨度从0.25到8d。各种气溶胶光学性质(如单次散射反照率、吸收的波长依赖性和BC质量吸收系数，MACBC)随光化学老化而演变，具体演变取决于初始粒子的性质和条件。涂层对BC吸收(所谓的透镜效应)的影响很小，即使在光化学老化之后也是如此。BRC吸收率(MACBrC)的初始演化在不同烧伤之间有所不同，但随着老化时间的延长而持续下降；BRC吸收的波长依赖性通常随着年龄的增长而增加。观测到的BRC性质的变化是二次有机气溶胶(SOA)产生和原生和二次OA质量的非均质氧化共同作用的结果，其中SOA的产生是变化的主要驱动因素。SOA的性质随时间变化，既反映了具有相对于OH的寿命范围的前体的形成，也反映了腔室内不断演变的光化学环境。虽然BRC的吸收率通常会随着老化而降低，但稀释校正后的吸收实际上可能会因为产生SOA而增加。这些实验结果为解释生物质燃烧产生的烟羽中粒子光学性质演变的环境观测提供了背景。由哥白尼出版公司代表欧洲地球科学联盟出版。8512C.D.Cappa等人：生物质燃烧-来自各种燃料的衍生颗粒-第2部分
Particles in smoke emitted from biomass combustion have a large impact on global climate and urban air quality. There is limited understanding of how particle optical properties – especially the contributions of black carbon (BC) and brown carbon (BrC) – evolve with photochemical aging of smoke. We analyze the evolution of the optical properties and chemical composition of particles produced from combustion of a wide variety of biomass fuels, largely from the western United States. The smoke is photochemically aged in a reaction chamber over atmospheric-equivalent timescales ranging from 0.25 to 8 d. Various aerosol optical properties (e.g., the single-scatter albedo, the wavelength dependence of absorption, and the BC mass absorption coefficient, MACBC) evolved with photochemical aging, with the specific evolution dependent on the initial particle properties and conditions. The impact of coatings on BC absorption (the so-called lensing effect) was small, even after photochemical aging. The initial evolution of the BrC absorptivity (MACBrC) varied between individual burns but decreased consistently at longer aging times; the wavelength dependence of the BrC absorption generally increased with aging. The observed changes to BrC properties result from a combination of secondary organic aerosol (SOA) production and heterogeneous oxidation of primary and secondary OA mass, with SOA production being the major driver of the changes. The SOA properties varied with time, reflecting both formation from precursors having a range of lifetimes with respect to OH and the evolving photochemical environment within the chamber. Although the absorptivity of BrC generally decreases with aging, the dilution-corrected absorption may actually increase from the production of SOA. These experimental results provide context for the interpretation of ambient observations of the evolution of particle optical properties in biomass-combustion-derived smoke plumes. Published by Copernicus Publications on behalf of the European Geosciences Union. 8512 C. D. Cappa et al.: Biomass-burning-derived particles from a wide variety of fuels – Part 2