Photodegradation of Secondary Organic Aerosol Material Quantified with a Quartz Crystal Microbalance,Environmental Science & Technology Letters

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Photodegradation of Secondary Organic Aerosol Material Quantified with a Quartz Crystal Microbalance
Environmental Science & Technology Letters ( IF 8.9 ) Pub Date : 2018-05-21 , DOI: 10.1021/acs.estlett.8b00231
Kurtis T. Malecha ₁ , Zicheng Cai ₁ , Sergey A. Nizkorodov ₁

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We used a quartz crystal microbalance (QCM) to quantify the mass loss resulting from exposure of secondary organic aerosol (SOA) particles deposited on the QCM crystal to 254, 305, and 365 nm radiation. We coupled the QCM setup to a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) to chemically resolve the photoproduced volatile organic compounds (VOCs) responsible for the mass loss. The photoproduced VOCs detected by the PTR-ToF-MS accounted for ∼50% of the mass loss rates measured with the QCM. Weakly absorbing SOA produced by ozonolysis of α-pinene or d-limonene exhibited a much larger mass loss rate in both the QCM and the PTR-ToF-MS data compared to that of strongly absorbing SOA produced by photooxidation of guaiacol. We predict that the fractional mass loss rate of α-pinene ozonolysis SOA should be as high as ∼1%/h on the summer solstice in Los Angeles in the lower troposphere and ∼4%/h in the stratosphere. The mass loss rates for SOA particles crossing a typical 254 nm oxidation flow reactor, which is routinely used for rapid aging of organic aerosol particles, are expected to be negligible because of the short residence time inside the reactor.

中文翻译：

石英晶体微天平定量的二次有机气溶胶材料的光降解

我们使用石英晶体微量天平（QCM）来量化由于沉积在QCM晶体上的次要有机气溶胶（SOA）颗粒暴露于254、305和365 nm辐射而导致的质量损失。我们将QCM设置与质子转移反应飞行时间质谱仪（PTR-ToF-MS）结合使用，以化学方式解决造成质量损失的光生挥发性有机化合物（VOC）。通过PTR-ToF-MS检测到的照片产生的VOC约占QCM测得质量损失率的50％。与强吸收愈创木酚的光氧化产生的SOA相比，通过α-pine烯或d-柠檬烯的臭氧分解产生的弱吸收SOA在QCM和PTR-ToF-MS数据中均表现出更大的质量损失率。我们预测，对流层下部低层洛杉矶的夏至时，α-pine烯臭氧分解SOA的质量损失率应高达〜1％/ h，而在平流层中则为〜4％/ h。穿过常规254 nm氧化流反应器的SOA颗粒的质量损失率由于在反应器内部的停留时间短而被认为可以忽略不计，该质量损失率通常用于有机气溶胶颗粒的快速老化。

更新日期：2018-05-21

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