Atmospheric secondary organic aerosols (SOAs), formed from condensable oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs), are important constituents of the atmosphere accounting for a significant fraction of ambient tropospheric aerosol. In this study, the formation of SOAs from the gas-phase ozonolysis of γ-terpinene (1-isopropyl-4-methyl-1,4-cyclohexadiene), a monoterpene emitted by many different trees (elm, cypress, water hickory, maple trees …) has been studied in an indoor atmospheric simulation chamber (CHARME), at 294 ± 2 K, atmospheric pressure, under dry conditions (relative humidity, RH < 2%) and in absence of seed particles. The concentration of γ-terpinene was measured by a proton Transfer Reaction - Time of Flight - Mass Spectrometer (PTR-ToF-MS), that of ozone by an UV photometric analyzer and the aerosol mass concentration was monitored using a scanning mobility particle sizer (SMPS). Scanning electronic microscopy (SEM) observations were performed to characterize the physical state and morphology of the formed SOAs. They show the formation of spherical particles in a viscous state.

The overall organic aerosol yield (Y) was determined as the ratio of the suspended aerosol mass concentration corrected for wall losses (M_o) to the total reacted γ-terpinene concentration, assuming a particle density of 1 g cm⁻³. The aerosol formation yield increases as the initial γ-terpinene concentration raises. The presence of an OH radical scavenger (cyclohexane) leads to a decrease in the SOA yields (they varied from 0.11 to 0.54 and from 0.16 to 0.49, without and with, an OH radical scavenger, respectively). Y is a strong function of M_o and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model.

大气二次有机气溶胶 (SOA) 由人为和生物挥发性有机化合物 (VOC) 的可冷凝氧化产物形成，是大气的重要成分，占环境对流层气溶胶的很大一部分。在这项研究中，γ-萜品烯（1-异丙基-4-甲基-1,4-环己二烯）的气相臭氧分解形成 SOA，这是一种由许多不同树木（榆树、柏树、水胡桃木、枫树）排放的单萜树木……) 在室内大气模拟室 (CHARME) 中进行了研究，在 294 ± 2 K、大气压、干燥条件（相对湿度，RH < 2%）和没有种子颗粒的情况下。γ-萜品烯的浓度通过质子转移反应-飞行时间-质谱仪（PTR-ToF-MS）测量，通过紫外光度分析仪检测臭氧，并使用扫描迁移率粒度仪 (SMPS) 监测气溶胶质量浓度。进行扫描电子显微镜 (SEM) 观察以表征形成的 SOA 的物理状态和形态。它们显示了粘性状态下球形颗粒的形成。

假设颗粒密度为 1 g cm ^-3，总有机气溶胶产率 (Y) 被确定为针对壁损失 (M _o )校正的悬浮气溶胶质量浓度与总反应的 γ-萜品烯浓度的比率。随着初始 γ-萜品烯浓度升高，气溶胶形成产率增加。OH 自由基清除剂（环己烷）的存在导致 SOA 产率降低（它们分别在 0.11 到 0.54 和 0.16 到 0.49 之间变化，没有和有 OH 自由基清除剂）。Y 是 M _o的强函数，有机气溶胶的形成可以用单产物气体/颗粒分配吸收模型表示。