Acid-catalyzed reactions between gas- and particle-phase constituents are critical to atmospheric secondary organic aerosol (SOA) formation. The aerosol-phase state is thought to influence the reactive uptake of gas-phase precursors to aerosol particles by altering diffusion rates within particles. However, few experimental studies have explored the precise role of the aerosol-phase state on reactive uptake processes. This laboratory study systematically examines the reactive uptake coefficient (γ) of trans-β-isoprene epoxydiol (trans-β-IEPOX), the predominant IEPOX isomer, on acidic sulfate particles coated with SOA derived from α-pinene ozonolysis. γ_IEPOX is obtained for core-shell particles, the morphology of which was confirmed by microscopy, as a function of SOA coating thickness and relative humidity. γ_IEPOX is reduced, in some cases by half of the original value, when SOA coatings are present prior to uptake, especially when coating thicknesses are >15 nm. The diurnal trend of IEPOX lost to acid-catalyzed reactive uptake yielding SOA compared with other known atmospheric sinks (gas-phase oxidation or deposition) is derived by modeling the experimental coating effect with field data from the southeastern United States. IEPOX-derived SOA is estimated to be reduced by 16–27% due to preexisting organic coatings during the afternoon (12:00 to 7:00 p.m., local time), corresponding to the period with the highest level of production.

中文翻译：

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异戊二烯衍生的环氧二醇（IEPOX）的反应性吸收对气溶胶相态对次生有机气溶胶形成的影响

气相和颗粒成分之间的酸催化反应对于大气中次级有机气溶胶（SOA）的形成至关重要。认为气溶胶相状态通过改变颗粒内的扩散速率来影响气相前体对气溶胶颗粒的反应性吸收。但是，很少有实验研究探索气溶胶相态对反应性摄取过程的精确作用。这项实验室研究系统地检查了主要的IEPOX异构体反式-β-异戊二烯环氧二醇（反式-β-IEPOX）在由α-pine烯臭氧分解得到的SOA包覆的酸性硫酸盐颗粒上的反应吸收系数（γ）。γ _IEPOX对于芯-壳颗粒，获得了SO 2，其形态通过显微镜确认，其为SOA涂层厚度和相对湿度的函数。γ _IEPOX是由原始值的一半减少，在一些情况下，当SOA涂层是本之前摄取，特别是当涂层厚度> 15nm以下。与其他已知的大气汇（气相氧化或沉积）相比，IEPOX在酸催化的反应性吸收中所产生的SOA的日变化趋势（气相氧化或沉积）与美国东南部的田间数据进行了模拟。估计IEPOX衍生的SOA减少了16–27％，这是由于下午（当地时间12:00至7:00 pm）预先存在有机涂层所致，这与生产水平最高的时期相对应。