Average chemical properties and potential formation pathways of highly oxidized organic aerosol
Average chemical properties and potential formation pathways of highly oxidized organic aerosol
复制标题
DOI：
10.1039/c3fd00045a
复制
发表时间：
2013-01-01
影响因子：
3.4
通讯作者：
Kroll, Jesse H.
中科院分区：
文献类型：
--
作者：
Daumit, Kelly E.;Kessler, Sean H.;Kroll, Jesse H.
环境有机气溶胶的测量表明，相当大的一部分是高度氧化和低挥发性，但这部分一般不再现无论是在实验室研究或模型。在这里，我们描述了一种新的方法来约束可行的前体和高度氧化的有机气溶胶的形成途径，从氧化产物开始，并考虑可能的逆反应，使用一组简单的化学规则。这项工作的重点是低挥发性氧化有机气溶胶（LV-OOA），气溶胶质谱仪数据的因子分析确定。气溶胶的元素组成和挥发性使得能够确定其在三维化学空间（由H/C、O/C和碳数定义）中的位置，从而确定其平均化学式。考虑可能的反反应，然后定义通过这个化学空间，限制潜在的反应途径和前体采取的运动。该方法适用于两种高度氧化的气溶胶类型，一种是来自十次现场活动的LV-OOA因子的平均值（平均公式C10.5H13.4O7.3），另一种是极端氧化的LV-OOA（来自墨西哥城，平均公式C10H12.1O8.4）。结果表明，潜在的形成途径包括功能化反应，每个氧化步骤添加多个官能团，高度氧化的前体的低聚反应，以及在某些情况下，碎片化反应，涉及小的，减少片段的损失。
Measurements of ambient organic aerosol indicate that a substantial fraction is highly oxidized and low in volatility, but this fraction is generally not reproduced well in either laboratory studies or models. Here we describe a new approach for constraining the viable precursors and formation pathways of highly oxidized organic aerosol, by starting with the oxidized product and considering the possible reverse reactions, using a set of simple chemical rules. The focus of this work is low-volatility oxidized organic aerosol (LV-OOA), determined from factor analysis of aerosol mass spectrometer data. The elemental composition and volatility of the aerosol enable the determination of its position in a three-dimensional chemical space (defined by H/C, O/C, and carbon number) and thus its average chemical formula. Consideration of possible back-reactions then defines the movement taken through this chemical space, constraining potential reaction pathways and precursors. This approach is taken for two highly oxidized aerosol types, an average of LV-OOA factors from ten field campaigns (average formula C10.5H13.4O7.3), and extremely oxidized LV-OOA (from Mexico City, average formula C10H12.1O8.4). Results suggest that potential formation pathways include functionalization reactions that add multiple functional groups per oxidation step, oligomerization of highly oxidized precursors, and, in some cases, fragmentation reactions that involve the loss of small, reduced fragments.