Photodegradation of Secondary Organic Aerosols by Long-Term Exposure to Solar Actinic Radiation
Photodegradation of Secondary Organic Aerosols by Long-Term Exposure to Solar Actinic Radiation
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DOI：
10.1021/acsearthspacechem.0c00088
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发表时间：
2020-07-16
影响因子：
3.4
通讯作者：
Nizkorodov, Sergey A.
中科院分区：
文献类型：
--
作者：
Baboomian, Vahe J.;Gu, Yiran;Nizkorodov, Sergey A.
阳光驱动的二次有机气溶胶(SOA)的化学转化对于理解大气颗粒物的气候和健康相关特性很重要，但这些光化学过程还没有被很好地理解。我们通过观察多天的紫外光照射下的凝聚相光化学过程来测量SOA光降解率。实验利用石英晶体微天平，定量测定了在高NOx和低NOx条件下，D-柠檬烯和α-品烯臭氧化和甲苯光氧化制备的SOA材料的质量损失率。我们观察到254 nm的辐照在24小时后几乎完全降解了SOA，甲苯衍生的SOA的质量损失率更高，在254 nm处有很强的吸收。305 nm的辐射对对流层的影响更大，即使甲苯+衍生的SOA有较高的吸收系数，但由α-蒎烯和D-柠檬烯生成的SOA的质量损失率较大。在所有的305 nm辐照实验中，初始质量损失率都很高(相当于每小时1-5%的质量损失分数)，但在照射24小时后，它的速度变慢，光阻部分的SOA光降解速度要慢得多(
Sunlight-driven chemical transformations of secondary organic aerosol (SOA) are important for understanding the climate- and health-relevant properties of atmospheric particulate matter, but these photochemical processes are not well understood. We measured the photodegradation rates of SOA by observing condensed-phase photochemical processes over many days of UV exposure. The experiments relied on a quartz crystal microbalance to quantify the mass loss rate from SOA materials prepared by ozonolysis of D-limonene and alpha-pinene and photo-oxidation of toluene under either high or low NOx conditions. We observed that 254 nm irradiation degraded SOA almost entirely after 24 h. The mass loss rates were higher for toluene-derived SOA, which absorbs strongly at 254 nm. Irradiation at 305 nm, which is more relevant for the troposphere, resulted in larger mass loss rates from SOA generated from alpha-pinene and D-limonene, even though toluene+derived SOA had a higher absorption coefficient. In all 305 nm irradiation experiments, the initial mass loss rate was high (corresponding to 1-5% fractional mass loss per hour), but it slowed down after 24 h of irradiation, with a photorecalcitrant fraction of SOA degrading much slower (