Density and elemental ratios of secondary organic aerosol: Application of a density prediction method
Density and elemental ratios of secondary organic aerosol: Application of a density prediction method
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DOI：
10.1016/j.atmosenv.2012.11.006
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发表时间：
2013-04
影响因子：
5
通讯作者：
S. Nakao;P. Tang;Xiaochen Tang;Christopher H. Clark;Li Qi;Eric Seo;A. Asa-Awuku;D. Cocker
中科院分区：
文献类型：
--
作者：
S. Nakao;P. Tang;Xiaochen Tang;Christopher H. Clark;Li Qi;Eric Seo;A. Asa-Awuku;D. Cocker
有机材料密度是气溶胶科学的基本参数，但直接测量并不容易实现。本研究研究了 22 种不同分子大小 (C5∼C15) 的不同挥发性有机化合物在环境室中氧化形成的二次有机气溶胶 (SOA) 的密度和元素比。与较小碳数的反应物（例如，苯酚 SOA：1.43 g cm−3）相比，具有较大碳数的反应物产生密度较低的 SOA（例如，β-石竹烯 SOA：1.22 g cm−3），这与母体分子不同程度的氧化一致。最近的一项研究提出了元素比率（O/C 和 H/C）与有机材料密度之间的半经验关系（Kuwata 等人，2012）。其中的预测方法是根据本研究在加州大学河滨分校/CE-CERT 环境室获得的大型实验数据集进行评估的。正如 Kuwata 等人所述，预测的颗粒密度与实验测量值的吻合度在 12% 以内。 (2012)，C6 化合物（苯、苯酚和儿茶酚）除外。因此，应用范围进一步扩大到包括人为（芳香）系统。氮和硫对密度预测的影响仍不清楚。
Organic material density is a fundamental parameter in aerosol science, yet direct measurement is not readily available. This study investigates density and elemental ratios of secondary organic aerosol (SOA) formed by the oxidation of 22 different volatile organic compounds with a wide range of molecular size (C5∼C15) in an environmental chamber. Reactants with a larger number of carbons yielded SOA with lower density (e.g., β-caryophyllene SOA: 1.22 g cm−3) compared with smaller ones (e.g., phenol SOA: 1.43 g cm−3) consistent with different extents of oxidation of the parent molecule. A recent study proposed a semi-empirical relationship between elemental ratios (O/C and H/C) and organic material density (Kuwata et al., 2012). The prediction method therein is evaluated against the large experimental data set of this study acquired in the UC Riverside/CE-CERT environmental chamber. The predicted particle densities agree with experimental measurements within 12% as stated by Kuwata et al. (2012) except for C6 compounds (benzene, phenol, and catechol). Therefore, the range of application has been further extended to include anthropogenic (aromatic) systems. The effects of nitrogen and sulfur on the density prediction remain unclear.