Using Ionic Liquids To Study the Migration of Semivolatile Organic Vapors in Smog Chamber Experiments
Using Ionic Liquids To Study the Migration of Semivolatile Organic Vapors in Smog Chamber Experiments
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利用离子液体研究烟雾室实验中半挥发性有机蒸气的迁移
DOI：
10.1021/acs.jpca.9b02847
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Donahue, Neil M.
中科院分区：
文献类型：
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作者：
Ye, Qing;Sullivan, Ryan C.;Donahue, Neil M.
大气有机气溶胶由多种化合物组成的复杂混合物，具有多种结构和挥发性。为了了解大气有机气溶胶的去向及其对颗粒物污染的贡献，我们需要研究半挥发性有机化合物（SVOC）和低挥发性有机化合物（LVOC）之间的相对比例。 SVOC 可以有效地在气溶胶群体之间迁移和交换，因此更容易进行进一步的反应和去除过程，而 LVOC 基本上会停留在颗粒相。在这里，我们介绍在烟雾室实验中使用离子液体液滴作为有机蒸气的新型吸附剂，以研究气溶胶群体之间的成分转移，并从室产生的二次有机气溶胶（SOA）中分离SVOC和LVOC。 SOA 形成并凝结在硫酸铵晶种上，随后将离子液体液滴引入腔室中。我们表明，α-蒎烯臭氧分解产生的 LVOC 和 SVOC 都有相当大的产率，并且随着反应的 α-蒎烯量的增加，离子液体对 SVOC 的吸收也增加。我们还表明，与最初凝结在硫酸铵晶种上的 SOA 相比，吸收到离子液体中的 SVOC 更容易再蒸发。因此，我们能够将分配到极极性离子液体气溶胶中的半挥发性成分与也凝结在硫酸铵晶种上的明显不易挥发的成分区分开来。结合之前使用其他有机气溶胶作为溶剂来探测气溶胶群体之间 SVOC 转移的研究，我们提供了一系列广泛的测量来探测和约束室产生的 SOA 复合物的物理和热力学特性。
Atmospheric organic aerosols comprise complex mixtures of a myriad of compounds with a wide range of structures and volatilities. To understand the fate of atmospheric organic aerosols and their contribution to particulate matter pollution, we need to study the relative portion divided between semivolatile organic compounds (SVOCs) and low-volatility organic compounds (LVOCs). SVOCs can effectively migrate and exchange between aerosol populations and thus are more accessible for further reactions and removal processes, while LVOCs will essentially stay in the particle phase. Here, we introduce using ionic liquid droplets as novel sorbents for organic vapors in smog chamber experiments to study the transfer of constituents between aerosol populations and to separate SVOCs and LVOCs from chamber-produced secondary organic aerosols (SOAs). SOA was formed and condensed on the ammonium-sulfate seeds, and later ionic liquid droplets were introduced into the chamber. We show that there are considerable yields of both LVOCs and SVOCs produced from α-pinene ozonolysis, and the uptake of SVOCs into the ionic liquid increases as the amount of reacted α-pinene increases. We also show that the SVOCs absorbed into the ionic liquid re-evaporate more readily compared to SOA originally condensed on the ammonium-sulfate seeds. We are thus able to differentiate the semivolatile components that partition into the extremely polar ionic liquid aerosols from the demonstrably less volatile components also condensed on the ammonium-sulfate seeds. Combined with previous studies using other organic aerosols as solvents to probe SVOC transfer between aerosol populations, we provide a wide set of measurements to probe and constrain the physical and thermodynamic properties of chamber-produced SOA complex.