Chemical Structure Regulates the Formation of Secondary Organic Aerosol and Brown Carbon in Nitrate Radical Oxidation of Pyrroles and Methylpyrroles
Chemical Structure Regulates the Formation of Secondary Organic Aerosol and Brown Carbon in Nitrate Radical Oxidation of Pyrroles and Methylpyrroles
复制标题
化学结构调节吡咯和甲基吡咯硝酸盐自由基氧化中二次有机气溶胶和棕碳的形成
DOI：
10.1021/acs.est.2c02345
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发表时间：
2022
影响因子：
11.4
通讯作者：
Zhang, Haofei
中科院分区：
文献类型：
--
作者：
Mayorga, Raphael;Chen, Kunpeng;Raeofy, Nilofar;Woods, Megan;Lum, Michael;Zhao, Zixu;Zhang, Wen;Bahreini, Roya;Lin, Ying-Hsuan;Zhang, Haofei
含氮杂环挥发性有机化合物（VOCs）是野火排放物的重要组成部分，在夜间容易与硝酸根（NO3）发生反应，但其氧化机制以及二次有机气溶胶（SOA）和棕色碳（BrC）的潜在形成尚不清楚。在这里，NO3氧化的三个含氮杂环VOCs，吡咯，1-甲基吡咯（1-MP），2-甲基吡咯（2-MP），在室内实验中进行了研究，以确定SOA和BrC形成的前体结构的影响。使用一套在线和离线仪器分析SOA的化学组成和光学性质。二硝基和三硝基产物被认为是占主导地位的SOA成分吡咯和2-MP，但没有观察到从1-MP。此外，2-MP和吡咯的SOA表现出较强的光吸收，而1-MP的SOA主要是散射。从这些结果中，我们建议，NO3-引发的氢从吡咯和2-MP的1-位的自由基移位和NO2加成后，导致光吸收的硝基芳香族产品的提取。在没有1位氢的情况下，NO3加成可能主导1-MP化学。我们还估计，总的SOA质量和光吸收吡咯和2-MP是可比的酚类挥发性有机化合物和甲苯在生物质燃烧，强调夜间氧化的吡咯和甲基吡咯在空气质量和气候模型的重要性。
Nitrogen-containing heterocyclic volatile organic compounds (VOCs) are important components of wildfire emissions that are readily reactive toward nitrate radicals (NO3) during nighttime, but the oxidation mechanism and the potential formation of secondary organic aerosol (SOA) and brown carbon (BrC) are unclear. Here, NO3oxidation of three nitrogen-containing heterocyclic VOCs, pyrrole, 1-methylyrrole (1-MP), and 2-methylpyrrole (2-MP), was investigated in chamber experiments to determine the effect of precursor structures on SOA and BrC formation. The SOA chemical compositions and the optical properties were analyzed using a suite of online and offline instrumentation. Dinitro- and trinitro-products were found to be the dominant SOA constituents from pyrrole and 2-MP, but not observed from 1-MP. Furthermore, the SOA from 2-MP and pyrrole showed strong light absorption, while that from 1-MP were mostly scattering. From these results, we propose that NO3-initiated hydrogen abstraction from the 1-position in pyrrole and 2-MP followed by radical shift and NO2addition leads to light-absorbing nitroaromatic products. In the absence of a 1-position hydrogen, NO3addition likely dominates the 1-MP chemistry. We also estimate that the total SOA mass and light absorption from pyrrole and 2-MP are comparable to those from phenolic VOCs and toluene in biomass burning, underscoring the importance of considering nighttime oxidation of pyrrole and methylpyrroles in air quality and climate models.