Collection efficiency of α -pinene secondary organic aerosol particles explored via light-scattering single-particle aerosol mass spectrometry
Collection efficiency of α -pinene secondary organic aerosol particles explored via light-scattering single-particle aerosol mass spectrometry
复制标题
通过光散射单颗粒气溶胶质谱法探索α-蒎烯二次有机气溶胶颗粒的收集效率
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发表时间：
2016
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通讯作者：
N. Donahue
中科院分区：
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作者：
E. Robinson;T. Onasch;D. Worsnop;N. Donahue
抽象的。我们利用气溶胶质谱仪 (AMS) 的单颗粒能力研究了由 α-蒎烯 + O3 制成的二次有机气溶胶 (SOA) 颗粒的收集效率和有效电离效率。这些实验中 SOA 的平均基于计数的收集效率 (CEp) 为 0.30 (±0.04 SD)，范围从 0.25 到 0.40。基于质量的平均收集效率 (CEm) 为 0.49 (±0.07 SD)。这种子单元收集效率和延迟汽化可归因于汽化区域中的粒子弹跳。通过对 AMS 的光散射单粒子 (LSSP) 模块进行光学和化学耦合检测，我们提供了明确的证据，证明延迟蒸发对于这些粒子来说有些用词不当：作为 AMS 质量分布一部分测量的 SOA 粒子不会以缓慢的速率蒸发；相反，它们会闪蒸，尽管通常不是在与汽化器的初始撞击时而是在随后与汽化区域中的热表面撞击时发生。我们还发现有效电离效率（定义为每个粒子的离子数，IPP）随着到达时间的延迟而降低。 CEp 不是颗粒尺寸的函数（对于所研究的迁移直径范围为 170-460 nm），但我们确实看到 CEp 随着热解器温度的升高而降低，这意味着氧化态和/或挥发性会影响 SOA 的 CEp。通过测量单分散颗粒产生的每个颗粒的平均离子数作为信号延迟时间的函数，我们可以分别确定 CEp 和 CEm，从而更准确地测量不同颗粒类型的相对电离效率（与硝酸铵相比）。
Abstract. We investigated the collection efficiency and effective ionization efficiency for secondary organic aerosol (SOA) particles made from α-pinene + O3 using the single-particle capabilities of the aerosol mass spectrometer (AMS). The mean count-based collection efficiency (CEp) for SOA across these experiments is 0.30 (±0.04 SD), ranging from 0.25 to 0.40. The mean mass-based collection efficiency (CEm) is 0.49 (±0.07 SD). This sub-unit collection efficiency and delayed vaporization is attributable to particle bounce in the vaporization region. Using the coupled optical and chemical detection of the light-scattering single-particle (LSSP) module of the AMS, we provide clear evidence that delayed vaporization is somewhat of a misnomer for these particles: SOA particles measured as a part of the AMS mass distribution do not vaporize at a slow rate; rather, they flash-vaporize, albeit often not on the initial impact with the vaporizer but instead upon a subsequent impact with a hot surface in the vaporization region. We also find that the effective ionization efficiency (defined as ions per particle, IPP) decreases with delayed arrival time. CEp is not a function of particle size (for the mobility diameter range investigated, 170–460 nm), but we did see a decrease in CEp with thermodenuder temperature, implying that oxidation state and/or volatility can affect CEp for SOA. By measuring the mean ions per particle produced for monodisperse particles as a function of signal delay time, we can separately determine CEp and CEm and thus more accurately measure the relative ionization efficiency (compared to ammonium nitrate) of different particle types.