Molecular size evolution of oligomers in organic aerosols collected in urban atmospheres and generated in a smog chamber.
Molecular size evolution of oligomers in organic aerosols collected in urban atmospheres and generated in a smog chamber.
复制标题
在城市大气中收集并在烟雾室中产生的有机气溶胶中低聚物的分子大小演变。
DOI：
10.1021/es0525760
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发表时间：
2006
影响因子：
11.4
通讯作者：
V. Samburova
中科院分区：
文献类型：
--
作者：
M. Kalberer;M. Sax;V. Samburova
只有一小部分的总有机气溶胶质量可以在分子水平上解决。有机气溶胶中的高分子量化合物最近得到了广泛的关注，因为这类化合物可能解释了无法解释的有机气溶胶质量的主要部分。这些化合物已被确定与不同的质谱方法，分子量高达1000 Da的化合物被发现在二次有机气溶胶（SOA）产生的芳香族和萜烯前体在烟雾室实验。在这里，我们应用基质辅助激光解吸/电离质谱（MALDI-MS）SOA颗粒从两个生物的前体，α-蒎烯和异戊二烯。在这两个SOA系统中发现了类似的低聚物模式，但也在三甲苯（一种人为SOA前体）的SOA中发现。然而，不同的最大分子尺寸测量这三个SOA系统。虽然α-蒎烯和异戊二烯中的低聚物具有大多低于600-700 Da的尺寸，但它们在三甲基苯-SOA中增长至约1000 Da。低聚物的最终分子尺寸在颗粒老化过程中较早达到，而与老化相关的其他颗粒性质，例如总酸浓度或低聚物浓度，在长得多的时间尺度上连续增加。低聚物分子尺寸增长的动力学行为可以用链增长动力学机制来解释。在环境气溶胶样品的水提取物中测量了类似的低聚物质量模式（用相同的技术测量）。观察到夏季和冬季之间的明显差异。在夏季的几个单一的质量峰的强度比冬季高得多，指出这些化合物在冬季和夏季的形成过程中可能存在差异。
Only a minor fraction of the total organic aerosol mass can be resolved on a molecular level. High molecular weight compounds in organic aerosols have recently gained much attention because this class of compound potentially explains a major fraction of the unexplained organic aerosol mass. These compounds have been identified with different mass spectrometric methods, and compounds with molecular masses up to 1000 Da are found in secondary organic aerosols (SOA) generated from aromatic and terpene precursors in smog chamber experiments. Here, we apply matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to SOA particles from two biogenic precursors, alpha-pinene and isoprene. Similar oligomer patterns are found in these two SOA systems, but also in SOA from trimethylbenzene, an anthropogenic SOA precursor. However, different maxima molecular sizes were measured for these three SOA systems. While oligomers in alpha-pinene and isoprene have sizes mostly below 600-700 Da, they grow up to about 1000 Da in trimethylbenzene-SOA. The final molecular size of the oligomers is reached early during the particle aging process, whereas other particle properties related to aging, such as the overall acid concentration or the oligomer concentration, increase continuously over a much longer time scale. This kinetic behavior of the oligomer molecular size growth can be explained by a chain growth kinetic regime. Similar oligomer mass patterns were measured in aqueous extracts of ambient aerosol samples (measured with the same technique). Distinct differences between summer and winter were observed. In summer a few single mass peaks were measured with much higher intensity than in winter, pointing to a possible difference in the formation processes of these compounds in winter and summer.