Laboratory Insights into the Diel Cycle of Optical and Chemical Transformations of Biomass Burning Brown Carbon Aerosols.
Laboratory Insights into the Diel Cycle of Optical and Chemical Transformations of Biomass Burning Brown Carbon Aerosols.
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DOI：
10.1021/acs.est.0c04310
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发表时间：
2020-10-06
影响因子：
11.4
通讯作者：
Rudich Y
中科院分区：
文献类型：
--
作者：
Li C;He Q;Fang Z;Brown SS;Laskin A;Cohen SR;Rudich Y
生物质燃烧棕色碳气溶胶（BB-BrC）在其昼夜生命周期的变化目前还没有得到很好的研究。采用串列流动反应器研究了在黑暗条件下NO3·处理BB焦油代用气溶胶后，其光化学OH·反应和光解的老化过程。结果表明，在黑暗中的O3氧化减少木焦油气溶胶的光吸收，导致更高的粒子单散射（SSA）。NO3·反应通过形成二次发色团（例如硝基芳香族化合物（NACs）和有机硝酸盐），使气溶胶的质量吸收系数（MAC）增加2-3倍。随后的OH·氧化和直接光解都分解了NO3·老化木焦油气溶胶中的有机硝酸盐（ONs，代表NAC和有机硝酸盐的本体官能度），从而降低了颗粒物的吸收。此外，通过光化学老化，NAC比有机硝酸酯降解得更快。NO3·老化的木焦油气溶胶更容易发生光解反应而不是OH·反应。NO3·老化气溶胶的光分解寿命和吸收寿命在典型的太阳辐射下大约为小时，而OH·氧化的吸收寿命和光寿命则要长得多。总的来说，夜间老化通过NO3·反应增加了木焦油气溶胶的光吸收，并缩短了它们在白天条件下的吸收寿命。
Transformations of biomass burning brown carbon aerosols (BB-BrC) over their diurnal lifecycle are currently not well studied. In this study, the aging of BB tar proxy aerosols processed by NO3• under dark conditions followed by the photochemical OH• reaction and photolysis were investigated in tandem flow reactors. The results show that O3 oxidation in the dark diminishes light absorption of wood tar aerosols, resulting in higher particle single-scattering albedo (SSA). NO3• reactions augment the mass absorption coefficient (MAC) of the aerosols by a factor of 2–3 by forming secondary chromophores, such as nitroaromatic compounds (NACs) and organonitrates. Subsequent OH• oxidation and direct photolysis both decompose the organic nitrates (ONs, representing bulk functionalities of NACs and organonitrates) in the NO3•-aged wood tar aerosols, thus decreasing particle absorption. Moreover, NACs degrade faster than organonitrates by photochemical aging. The NO3•-aged wood tar aerosols are more susceptible to photolysis than to OH• reactions. The photolysis lifetimes for the ONs and for the absorbance of the NO3•-aged aerosols are on the order of hours under typical solar irradiation, while the absorption and ON lifetimes toward OH• oxidation are substantially longer. Overall, nighttime aging via NO3• reactions increases the light absorption of wood tar aerosols and shortens their absorption lifetime under daytime conditions.
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