Organic aerosol formation from the reactive uptake of isoprene epoxydiols (IEPOX) onto non-acidified inorganic seeds
Organic aerosol formation from the reactive uptake of isoprene epoxydiols (IEPOX) onto non-acidified inorganic seeds
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DOI：
10.5194/acp-14-3497-2014
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发表时间：
2013-10
影响因子：
6.3
通讯作者：
Tran B. Nguyen;M. Coggon;K. Bates;Xuan Zhang;R. Schwantes;K. Schilling;C. L. Loza;R. Flagan;P. Wennberg;J. Seinfeld
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文献类型：
--
作者：
Tran B. Nguyen;M. Coggon;K. Bates;Xuan Zhang;R. Schwantes;K. Schilling;C. L. Loza;R. Flagan;P. Wennberg;J. Seinfeld
在不添加酸的情况下，研究了顺式和反式β- ipox在水合无机种子颗粒上的反应分配。干燥的硫酸铵（AS）未观察到有机气溶胶（OA）的形成；然而，当液水含量为总颗粒质量的40-75%时，顺式和反式β-IEPOX在AS种子上迅速有效地生长。从ipox中形成OA是一个动力学受限的过程，因此，如果存在气相ipox储层，OA将继续增长。在误差范围内，由于顺/反异构体结构，OA的生长或组成似乎没有差异。添加碱（NaOH）的水合AS种子对ipox的反应性吸收也产生了高OA负荷，这表明ipox对AS颗粒形成OA的pH依赖性较弱。在以Na^+取代NH^(+)_(4)的种子颗粒干燥后，未观察到OA的形成。在NaCl颗粒（离子强度~9 M）上测得ipox的亨利定律分配为3 × 10^7 M atm^−1（−50 / +100%）。当NH4+存在时，颗粒中产生少量的OA，但氯离子（Cl-）阴离子取代了硫酸盐(SO^(2-)_(4))，这可能表明阴离子亲核强度的差异。在线飞行时间气溶胶质谱和离线过滤分析提供了颗粒有机成分中含氧碳氢化合物，有机硫酸盐和胺的证据。结果与实地研究中观察到的iepox衍生的OA与颗粒酸度或液态水之间的弱相关性一致，因为化学体系受亲核限制，而不受水或催化剂活性的限制。
The reactive partitioning of cis and trans β-IEPOX was investigated on hydrated inorganic seed particles, without the addition of acids. No organic aerosol (OA) formation was observed on dry ammonium sulfate (AS); however, prompt and efficient OA growth was observed for the cis and trans β-IEPOX on AS seeds at liquid water contents of 40–75% of the total particle mass. OA formation from IEPOX is a kinetically limited process, thus the OA growth continues if there is a reservoir of gas-phase IEPOX. There appears to be no differences, within error, in the OA growth or composition attributable to the cis / trans isomeric structures. Reactive uptake of IEPOX onto hydrated AS seeds with added base (NaOH) also produced high OA loadings, suggesting the pH dependence for OA formation from IEPOX is weak for AS particles. No OA formation, after particle drying, was observed on seed particles where Na^+ was substituted for NH^(+)_(4). The Henry's Law partitioning of IEPOX was measured on NaCl particles (ionic strength ~9 M) to be 3 × 10^7 M atm^−1 (−50 / +100%). A small quantity of OA was produced when NH4+ was present in the particles, but the chloride (Cl-) anion was substituted for sulfate (SO^(2-)_(4)), possibly suggesting differences in nucleophilic strength of the anions. Online time-of-flight aerosol mass spectrometry and offline filter analysis provide evidence of oxygenated hydrocarbons, organosulfates, and amines in the particle organic composition. The results are consistent with weak correlations between IEPOX-derived OA and particle acidity or liquid water observed in field studies, as the chemical system is nucleophile-limited and not limited in water or catalyst activity.