Formation of brown carbon via reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic precursors
Formation of brown carbon via reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic precursors
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DOI：
10.1016/j.atmosenv.2012.09.012
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发表时间：
2012-12
影响因子：
5
通讯作者：
K. Updyke;Tran B. Nguyen;S. Nizkorodov
中科院分区：
文献类型：
--
作者：
K. Updyke;Tran B. Nguyen;S. Nizkorodov
对臭氧（O3）和羟基自由基（OH）引发的各种生物源氧化产生的二次有机气溶胶（SOA）的过滤样品进行了研究。（异戊二烯、α-蒎烯、柠檬烯、α-雪松烯、α-蛇麻烯、法呢烯、松树叶精油、雪松叶精油）和人为的（十四烷、1，3，5-三甲基苯、萘）前体暴露于含有约100ppb气态氨（NH3）的潮湿空气。SOA化合物与NH3的反应导致产生吸光的"棕色碳"化合物，布朗宁的程度从没有可观察到的变化（异戊二烯SOA）到可见的颜色变化（柠檬烯SOA）。与溶解的铵（NH4+）盐（例如硫酸铵）的水相反应在产生棕色碳方面同样有效。通过在甲醇中提取已知量的SOA材料并记录其UV/维斯吸收光谱来量化老化SOA的波长依赖性质量吸收系数（MAC）。对于一个给定的前体，OH-产生的SOA有系统地降低MAC相比，O3-产生的SOA。最高MAC值，棕色碳从SOA的柠檬烯和倍半萜的O3氧化产生的，是可比的MAC值生物质燃烧颗粒，但大大小于MAC值的黑碳气溶胶。NH3/NH4 ++ SOA棕色碳气溶胶可能有助于气溶胶光密度在高浓度的NH3或硫酸铵和高的光化学活性的区域。
Filter samples of secondary organic aerosols (SOA) generated from the ozone (O3)- and hydroxyl radical (OH)-initiated oxidation of various biogenic (isoprene, α-pinene, limonene, α-cedrene, α-humulene, farnesene, pine leaf essential oils, cedar leaf essential oils) and anthropogenic (tetradecane, 1,3,5-trimethylbenzene, naphthalene) precursors were exposed to humid air containing approximately 100 ppb of gaseous ammonia (NH3). Reactions of SOA compounds with NH3resulted in production of light-absorbing “brown carbon” compounds, with the extent of browning ranging from no observable change (isoprene SOA) to visible change in color (limonene SOA). The aqueous phase reactions with dissolved ammonium (NH4+) salts, such as ammonium sulfate, were equally efficient in producing brown carbon. Wavelength-dependent mass absorption coefficients (MAC) of the aged SOA were quantified by extracting known amounts of SOA material in methanol and recording its UV/Vis absorption spectra. For a given precursor, the OH-generated SOA had systematically lower MAC compared to the O3-generated SOA. The highest MAC values, for brown carbon from SOA resulting from O3oxidation of limonene and sesquiterpenes, were comparable to MAC values for biomass burning particles but considerably smaller than MAC values for black carbon aerosols. The NH3/NH4++ SOA brown carbon aerosol may contribute to aerosol optical density in regions with elevated concentrations of NH3or ammonium sulfate and high photochemical activity.