Production of Formate via Oxidation of Glyoxal Promoted by Particulate Nitrate Photolysis
Production of Formate via Oxidation of Glyoxal Promoted by Particulate Nitrate Photolysis
复制标题
颗粒硝酸盐光解促进乙二醛氧化生产甲酸盐
DOI：
10.1021/acs.est.0c08199
复制
发表时间：
2021
影响因子：
11.4
通讯作者：
Chan Chak K.
中科院分区：
文献类型：
--
作者：
Zhang Ruifeng;Gen Masao;Fu Tzung-May;Chan Chak K.
颗粒硝酸盐光解作用可在水滴中产生氧化剂（即 OH、NO2 和 NO2-/HNO2），并可能在增加大气氧化能力方面发挥潜在作用。我们早期的工作报道了硝酸盐光解促进二氧化硫氧化产生硫酸盐。在这里，我们使用乙二醛作为模型前体来研究颗粒硝酸盐光解在乙二醛被 OH 自由基颗粒相氧化形成二次有机气溶胶 (SOA) 中的作用。在 300 nm 处照射含有硝酸钠和乙二醛的颗粒。有趣的是，在乙二醛颗粒相硝酸盐光解过程中的光氧化过程中，并未发现文献报道的典型氧化产物草酸、乙醛酸以及较高分子量的产物。相反，甲酸/甲酸盐的产生被发现是主要的氧化产物。当乙二醛浓度高于 3 M 时，我们发现随着乙二醛浓度的增加，甲酸/甲酸盐的生产率显着增加。这些结果表明，由于甲酸是一种挥发性物质，水性颗粒中硝酸盐光解产生的 OH 自由基对高浓度乙二醛的氧化可能不会对 SOA 的形成产生显着贡献。此外，最近根据最先进的化学模型对甲酸/甲酸盐浓度的预测低于地面和高海拔的环境观测值。本研究揭示了对甲酸/甲酸盐的产生以及大气中乙二醛汇的新见解，这可能部分缩小这两个物种的模型预测和现场测量之间的差距。
Particulate nitrate photolysis can produce oxidants (i.e., OH, NO2, and NO2–/HNO2) in aqueous droplets and may play a potential role in increased atmospheric oxidative capacity. Our earlier works have reported on the SO2oxidation promoted by nitrate photolysis to produce sulfate. Here, we used glyoxal as a model precursor to examine the role of particulate nitrate photolysis in the formation of secondary organic aerosol (SOA) from particle-phase oxidation of glyoxal by OH radicals. Particles containing sodium nitrate and glyoxal were irradiated at 300 nm. Interestingly, typical oxidation products of oxalic acid, glyoxylic acid, and higher-molecular-weight products reported in the literature were not found in the photooxidation process of glyoxal during nitrate photolysis in the particle phase. Instead, formic acid/formate production was found as the main oxidation product. At glyoxal concentration higher than 3 M, we found that the formic acid/formate production rate increases significantly with increasing glyoxal concentration. Such results suggest that oxidation of glyoxal at high concentrations by OH radicals produced from nitrate photolysis in aqueous particles may not contribute significantly to SOA formation since formic acid is a volatile species. Furthermore, recent predictions of formic acid/formate concentration from the most advanced chemical models are lower than ambient observations at both the ground level and high altitude. The present study reveals a new insight into the production of formic acid/formate as well as a sink of glyoxal in the atmosphere, which may partially narrow the gap between model predictions and field measurements in both species.