Brown carbon in atmospheric fine particles in Yangzhou, China: Light absorption properties and source apportionment
Brown carbon in atmospheric fine particles in Yangzhou, China: Light absorption properties and source apportionment
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扬州大气细颗粒物中棕碳的光吸收特性及来源解析
DOI：
10.1016/j.atmosres.2020.105028
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发表时间：
2020-11-01
影响因子：
5.5
通讯作者：
Ge, Xinlei
中科院分区：
文献类型：
--
作者：
Chen, Yanfang;Xie, Xinchun;Ge, Xinlei
吸光有机碳，又名，棕色碳（BrC）是空气质量恶化和全球辐射强迫的重要贡献者。本文研究了扬州市大气细颗粒物（PM2.5）中BrC的光学、化学性质及其来源。甲醇可溶性有机物（Abs（365，WSOC））和水溶性有机物（Abs（365，WSOC））在365 nm处的光吸收系数分别为13.50 +/- 7.03 M/m和6.08 +/- 4.30 M/m。甲醇可溶性BrC在365 nm处的质量吸收效率（MAE（365））（1.12 +/- 0.35 m（2）/g C）也高于水溶性BrC（0.75 +/- 0.29 m（2）/g C）。对于水溶性BrC，Abs（365）和MAE（365）通常随着其氧碳（O/C）比（O/C）和氧化态（OSc）的增加而降低，表明化学老化后的光漂白。Abs（365，WSOC）和MAE（365，WSOC）对氮碳比（N/C）和水溶性有机氮（ON）含量的正响应表明，ON是重要的BrC发色团。应用多元线性回归模型对正矩阵分解法分解的各因子对水溶性有机气溶胶（OA）的贡献进行Abs（365，WSOC）分配，得到各OA因子的MAE（365）值。总体而言，主要的OA来源，包括交通（18.9%），生物质燃烧（23.7%），和烹饪相关的OA（10.5%）一起主导了AbS（365，WSOC），尽管他们的总质量贡献只有约三分之一（31.9%）。然而，Abs（365，WSOC）的最大单一贡献者是氧化程度较低的次生OA（33.8%）;氧化程度较高的次生OA因子主导水溶性OA质量（50.8%），但其光吸收率最弱，仅占Abs（365，WSOC）的13.1%。
Light absorbing organic carbon, a.k.a., brown carbon (BrC) is an important contributor to air quality deterioration and global radiative forcing. This work studied optical, chemical properties and sources of BrC in fine particles (PM2.5) collected in Yangzhou, China. The light absorption coefficient at 365 nm of methanol-soluble organics (Abs(365,WSOC)) and water-soluble organics (Abs(365,WSOC)) were 13.50 +/- 7.03 M/m and 6.08 +/- 4.30 M/m, respectively. Mass absorption efficiency at 365 nm (MAE(365)) of methanol-soluble BrC (1.12 +/- 0.35 m(2)/gC) was also higher than water-soluble BrC (0.75 +/- 0.29 m(2)/g C). For water-soluble BrC, both Abs(365) and MAE(365) generally decreased with increases of its oxygen-to-carbon (O/C) ratios and oxidation states (OSc), indicative of photo-bleaching upon chemical ageing. Positive responses of Abs(365,WSOC) and MAE(365,WSOC) to nitrogento-carbon (N/C) ratios and water-soluble organic nitrogen (ON) contents reveal that ON species are important BrC chromophores. A multiple linear regression model was applied to apportion Abs(365,WSOC) to contributions of different factors resolved from positive matrix factorization on water-soluble organic aerosols (OA), and obtained MAE(365) values of different OA factors. Overall, primary OA sources including traffic (18.9%), biomass burning (23.7%), and cooking-related OA (10.5%) together dominated the AbS(365,WSOC) despite their total mass contribution was only about one third (31.9%). The largest single contributor of Abs(365,WSOC) however, was the less-oxidized secondary OA (33.8%); the more-oxidized secondary OA factor dominated water-soluble OA mass (50.8%), yet its light absorptivity was the weakest and contributed only 13.1% of Abs(365,WSOC).