Role of stabilized Criegee Intermediate in secondary organic aerosol formation from the ozonolysis of a-cedrene
Role of stabilized Criegee Intermediate in secondary organic aerosol formation from the ozonolysis of a-cedrene
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稳定 Criegee 中间体在α-雪松臭氧分解形成二次有机气溶胶中的作用
DOI：
10.1016/j.atmosenv.2014.05.063
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发表时间：
2014
影响因子：
5
通讯作者：
Fenping Cui
中科院分区：
文献类型：
--
作者：
Lei Yao;Yan Ma;Lin Wang;Jun Zheng;Alexei Khalizov;Mindong Chen;Yaoyao Zhou;Lu Qi;Fenping Cui
大气臭氧分解倍半萜是二次有机气溶胶（SOA）的重要来源。然而，Criegee中间体（CIs）反应形成SOA前体的机制以及环境条件的影响仍然不清楚。在环境室实验的基础上，结合气相和颗粒相产物的详细表征，我们提出证据表明，臭氧分解α-雪松烯产生的相当一部分CIs是稳定的，这些稳定的CIs （SCIs）的双分子反应在SOA前体的形成中起着关键作用。在一个4.5 m3的可折叠含氟聚合物室中，在OH自由基和SCI清除剂存在的各种条件下进行臭氧分解实验。直接测量臭氧分解过程中产生的SOA颗粒的大小和质量，并用于计算颗粒有效密度和质量产率。气体和颗粒产品通过几种质谱分析方法进行了分析。共鉴定出14个气相化合物和17个颗粒相化合物。主要气相产物是SCIs分子内反应产生的二次臭氧（SOZ）。多功能有机酸是主要的颗粒相产物。测定的气溶胶颗粒密度为1.04±0.03 ~ 1.38±0.03 g/cm3，根据反应条件的不同，气溶胶质量产率为（23.7±0.4）% ~(46.4±6.5)%。醋酸（一种脊髓损伤清除剂）的存在抑制了新颗粒的形成，但导致气溶胶质量产量的增加。相反，so2的加入显著地促进了新粒子的形成和总气溶胶产量。加入SCI清除剂CH3COOH和SO2后，计算的OH生成率从（62.4±4.9）%下降到（9.0±1.6）%，表明大部分激发的CIs被碰撞稳定，双分子反应可以抑制过氧化氢通道中scisvia的单分子分解。SCIs与so2反应生成重要的成核前体硫酸。从作为SCI清除剂添加的so2的消耗量来看，α-雪松臭氧分解中SCI的下限产率估计为~ 88%。我们的工作强调了SCIs在SOA形成中的关键作用，并观察了α-雪松臭氧分解的气相和颗粒相产物的组成。在评估倍半萜臭氧分解的大气相关性时，需要考虑倍半萜CIs与大气相关物种（例如SO2， H2O）的双分子反应。
Atmospheric ozonolysis of sesquiterpenes is an important source of secondary organic aerosols (SOA). The mechanisms by which Criegee Intermediates (CIs) react to form SOA precursors and the influence of environmental conditions, however, remain unclear. On the basis of environmental chamber experiments coupled with detailed characterization of gas-phase and particle-phase products, we present evidence that a significant fraction of CIs from ozonolysis of α-cedrene are stabilized and bimolecular reactions of these stabilized CIs (SCIs) play a key role in the formation of SOA precursors. Ozonolysis experiments were conducted in a 4.5 m3collapsible fluoropolymer chamber under various conditions in the presence of the OH radical and SCI scavengers. The size and mass of SOA particles produced during ozonolysis were measured directly and used for calculation of particle effective density and mass yield. Gaseous and particulate products were analyzed by several mass spectrometry methods. A total of 14 compounds in gas phase and 17 compounds in particle phase were tentatively identified. The major gas-phase products are secondary ozonides (SOZ) from intramolecular reactions of SCIs. Multifunctional organic acids are dominant particle-phase products. The measured density of aerosol particles is 1.04 ± 0.03 to 1.38 ± 0.03 g/cm3, and the aerosol mass yield is (23.7 ± 0.4)% to (46.4 ± 6.5)%, depending on reaction conditions. The presence of acetic acid, an SCI scavenger, inhibits new particle formation, but leads to increased aerosol mass yield. In contrast, the addition of SO2dramatically enhances new particle formation and total aerosol yield. The calculated OH formation yield decreases from (62.4 ± 4.9)% to (9.0 ± 1.6)% upon addition of SCI scavengers CH3COOH and SO2, indicating that a large fraction of excited CIs are collisionally stabilized and unimolecular decomposition of SCIsviathe hydroperoxide channel can be suppressed by bimolecular reactions. The reaction of SCIs with SO2leads to the formation of sulfuric acid, an important nucleation precursor. From the consumption of SO2added as SCI scavenger, a lower-limit yield of SCIs from α-cedrene ozonolysis is estimated at ∼88%. Our work underscores the key role of SCIs in SOA formation and observed composition of gas- and particle-phase products from α-cedrene ozonolysis. Bimolecular reactions of sesquiterpene CIs with atmospherically relevant species (e.g. SO2, H2O) need to be considered when assessing the atmospheric relevance of ozonolysis of sesquiterpenes.