Effects of Precursor Structure on First-Generation Photo-Oxidation Organic Aerosol Formation
Effects of Precursor Structure on First-Generation Photo-Oxidation Organic Aerosol Formation
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DOI：
10.3389/fenvs.2022.892389
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
D. Sofio;D. Long;T. Kohls;J. Kunz;M. Wentzel;D. Hanson
中科院分区：
文献类型：
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作者：
D. Sofio;D. Long;T. Kohls;J. Kunz;M. Wentzel;D. Hanson
研究了前体分子结构特征对二次有机气溶胶（SOA）生长的影响。测定了直链烷烃的SOA产率，一些含氧化合物，直至高度官能化的烃，最大的是β-carbellene。有机SOA产率通过与光解流动反应器中SO2的标准粒度变化进行比较来确定。SOA的形成开始与OH自由基从HONO光解，并继续与NO和NO2存在于个位数nmol/mol水平。通过SOA材料的冷凝生长直径为10 nm的种子颗粒，并且用纳米颗粒尺寸测量系统监测生长。环状化合物占主导地位的最高SOA产生的结构特征，其次是C-10物种的双键，直链烷烃和异戊二烯最无效。羰基导致显着增加的增长相比，烷烃，而醇，三键化合物，芳香族化合物和环氧化物仅略高于烷烃在生产SOA。当存在多于一个双键时，或者如在1，2-环氧癸-9-烯中所见，双键与另一官能团一起存在时，SOA产率显著增加。双键的位置也很重要，β-蒎烯的SOA产率大约是α-蒎烯的5倍。在我们的光解流动反应器中，第一代氧化产物被认为是SOA的主要贡献物种，因此前体的分子结构是决定性的。我们还进行了α-蒎烯光氧化的质子转移质谱测量，并观察到多功能硝酸盐和可能的过氧自由基的质量的显着信号。质谱仪测量也被用来估计HONO光解速率。
The effect of precursor molecular structural features on secondary organic aerosol (SOA) growth was investigated for a number of precursor functional groups. SOA yields were determined for straight chain alkanes, some oxygenated, up to highly functionalized hydrocarbons, the largest being β-caryophyllene. Organic SOA yield was determined by comparing to standard particle size changes with SO2 in a photolytic flow reactor. SOA formation was initiated with OH radicals from HONO photolysis and continued with NO and NO2 present at single-digit nmol/mol levels. Seed particles of ∼10 nm diameter grew by condensation of SOA material and growth was monitored with a nanoparticle sizing system. Cyclic compounds dominate as the highest SOA yielding structural feature, followed by C-10 species with double bonds, with linear alkanes and isoprene most ineffective. Carbonyls led to significant increases in growth compared to the alkanes while alcohols, triple-bond compounds, aromatics, and epoxides were only slightly more effective than alkanes at producing SOA. When more than one double bond is present, or a double bond is present with another functional group as seen with 1, 2-epoxydec-9-ene, SOA yield is notably increased. Placement of the double bond is important as well with β-pinene having an SOA yield approximately 5 times that of α-pinene. In our photolytic flow reactor, first-generation oxidation products are presumed to be the primary species contributing to SOA thus the molecular structure of the precursor is determinant. We also conducted proton-transfer mass spectrometry measurements of α-pinene photooxidation and significant signals were observed at masses for multifunctional nitrates and possibly peroxy radicals. The mass spectrometer measurements were also used to estimate a HONO photolysis rate.