Reactive Uptake of Isoprene Epoxydiols Increases the Viscosity of the Core of Phase-Separated Aerosol Particles
Reactive Uptake of Isoprene Epoxydiols Increases the Viscosity of the Core of Phase-Separated Aerosol Particles
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DOI：
10.1021/acsearthspacechem.9b00138
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发表时间：
2019-08-01
影响因子：
3.4
通讯作者：
Ault, Andrew P.
中科院分区：
文献类型：
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作者：
Olson, Nicole E.;Lei, Ziying;Ault, Andrew P.
大气氧化挥发性有机化合物，如异戊二烯，以及随后的缩合或非均相反应导致二次有机气溶胶（SOA）的形成，这是亚微米气溶胶的普遍成分。液相分离有机无机气溶胶颗粒已在实验室和现场观测到；然而，对于相分离的气溶胶颗粒，多相反应对气溶胶粘度的影响尚不清楚。在这项研究中，相分离的气溶胶颗粒与气态异戊二烯环氧二醇（IEPDX）反应，这是一种丰富的异戊二烯氧化产物。酸性硫酸盐颗粒(H2SO4 + (NH4)(2)SO4, pH = 1.4)被实验室生成的生物SOA （α -蒎烯+ O-3）和人为SOA（甲苯+ OH）包裹，形成核壳形态。与IEPDX反应后，相分离的气溶胶颗粒不再显示液核特征。相反，它们的形状变得不规则，在撞击基底后变得更高，并且两种SOA的扩散比都降低了，这意味着颗粒粘度的增加。由于a-蒎烯和甲苯的SOA已经是粘稠的，这表明堆芯的相态从液态转变为粘稠状态。可能促进这种相变的一个例子是IEPDX与无机硫酸盐反应生成有机硫酸盐，特别是在IEPDX扩散通过有机涂层后。气溶胶物理化学性质的改变表明，在含soa颗粒的大气寿命期间，相态是动态的，气溶胶颗粒和气态之间的多相化学反应导致气溶胶在吸收异戊二烯氧化产物（如IEPDX）后变得更粘稠。
Atmospheric oxidation of volatile organic compounds, such as isoprene, and subsequent condensation or heterogeneous reactions lead to the formation of secondary organic aerosol (SOA), a ubiquitous component of submicron aerosol. Liquid liquid phase-separated organic inorganic aerosol particles have been observed in the laboratory and field; however, the impacts of multiphase reactions on aerosol viscosity are not well understood for phase-separated aerosol particles. In this study, phase-separated aerosol particles were reacted with gaseous isoprene epoxydiol (IEPDX), an abundant isoprene oxidation product. Acidic sulfate particles (H2SO4 + (NH4)(2)SO4 at pH = 1.4) were coated with laboratory-generated biogenic SOA (alpha-pinene + O-3) and anthropogenic SOA (toluene + OH), resulting in a core shell morphology. After reaction with IEPDX, the phase-separated aerosol particles no longer displayed characteristics of a liquid core. Instead, they became irregularly shaped, taller after impaction onto substrates, and had decreased spreading ratios for both types of SOA, implying an increase in particle viscosity. As the SOA from a-pinene and toluene was already viscous, this is indicative of a change in phase state for the core from liquid to viscous state. An example reaction that may be facilitating this phase change is IEPDX reaction with inorganic sulfate to produce organosulfates, especially after IEPDX diffuses through the organic coating. The modification of the aerosol physicochemical properties suggests that phase state is dynamic over the atmospheric lifetime of SOA-containing particles, with multiphase chemistry between aerosol particles and gaseous species leading to more viscous aerosol after uptake of isoprene oxidation products (e.g., IEPDX).