A mass spectrometric study of secondary organic aerosols formed from the photooxidation of anthropogenic and biogenic precursors in a reaction chamber
A mass spectrometric study of secondary organic aerosols formed from the photooxidation of anthropogenic and biogenic precursors in a reaction chamber
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DOI：
10.5194/acp-6-5279-2006
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发表时间：
2006-11-20
影响因子：
6.3
通讯作者：
Coe, H.
中科院分区：
文献类型：
--
作者：
Alfarra, M. R.;Paulsen, D.;Coe, H.
Aerodyne 气溶胶质谱仪 (AMS) 用于在线测量在反应室中存在氮氧化物、二氧化氮和丙烯的情况下分别照射 1,3,5-三甲苯 (1,3,5-TMB) 和 α-蒎烯所产生的氧化产物的质谱特征和质量尺寸分布。质谱结果表明，两种前体产生的 SOA 具有高度氧化性质的大致相似的化学功能。然而，两个反应体系中 SOA 的微小质谱片段出现显着差异，表明它们具有不同的分子组成。在两种前体的光氧化产物中都观察到了含氮有机化合物，并且它们的形成似乎受到氮氧化物的时间变化的控制。尽管两个系统中光氧化产物的整体碎片模式在每个实验期间没有显着变化，但一些单独的质量碎片对总质量的贡献似乎受到辐照时间的影响。利用迁移率和真空空气动力学直径之间的关系，确定了不同粒径的 1,3,5-TMB 和 α-蒎烯 SOA 颗粒的有效密度。 1,3,5-TMB SOA 的有效密度范围为 1.35-1.40 g/cm(3)，而 α-蒎烯 SOA 的有效密度范围为 1.29-1.32 g/cm(3)。确定的有效密度不显示对照射时间的依赖性。结果表明，SOA 的进一步化学处理发生在真实大气中，因为 α-蒎烯和 1,3,5-TMB 实验结果都无法重现在受老化大陆有机气溶胶影响的环境位置测量的含羰基和多功能羧酸物质之间正确的相对产物分布。
An Aerodyne Aerosol Mass Spectrometer (AMS) has been utilised to provide on-line measurements of the mass spectral signatures and mass size distributions of the oxidation products resulting from irradiating 1,3,5-trimethylbenzene (1,3,5-TMB) and alpha-pinene, separately, in the presence of nitrogen oxide, nitrogen dioxide and propene in a reaction chamber. Mass spectral results indicate that both precursors produce SOA with broadly similar chemical functionality of a highly oxidised nature. However, significant differences occur in the minor mass spectral fragments for the SOA in the two reaction systems, indicating that they have different molecular composition. Nitrogen-containing organic compounds have been observed in the photooxidation products of both precursors, and their formation appeared to be controlled by the temporal variability of NOx. Although the overall fragmentation patterns of the photooxidation products in both systems did not change substantially over the duration of each experiment, the contribution of some individual mass fragments to total mass appeared to be influenced by the irradiation time. The effective densities of the 1,3,5-TMB and alpha-pinene SOA particles were determined for various particle sizes using the relationship between mobility and vacuum aerodynamic diameters. The effective density for the 1,3,5-TMB SOA ranged from 1.35-1.40 g/cm(3), while that for alpha-pinene SOA ranged from 1.29-1.32 g/cm(3). The determined effective densities did not show dependence on irradiation time. Results suggest that further chemical processing of SOA takes place in the real atmosphere, as neither the alpha-pinene nor the 1,3,5-TMB experimental results reproduce the right relative product distribution between carbonyl-containing and multifunctional carboxylic acid species measured at ambient locations influenced by aged continental organic aerosols.