Radical chemistry in the Pearl River Delta: observations and modeling of OH and HO 2 radicals in Shenzhen in 2018

作者：Xinping Yang, Keding Lu, Xuefei Ma, Yue Gao, Zhaofeng Tan, Haichao Wang, Xiaorui Chen, Xin Li, Xiaofeng Huang, Ling‐Yan He, Meng‐Xue Tang, Bo Zhu, Shiyi Chen, Huabin Dong, Limin Zeng, Yuanhang Zhang · 发表于：Atmospheric chemistry and physics · 年份：2022 · DOI：10.5194/acp-22-12525-2022 · 被引用次数：54 · 研究领域：Atmospheric chemistry and aerosols、Atmospheric Ozone and Climate、Air Quality Monitoring and Forecasting

Abstract. The ambient radical concentrations were measured continuously by laser-induced fluorescence during the STORM (STudy of the Ozone foRmation Mechanism) campaign at the Shenzhen site, located in the Pearl River Delta in China, in the autumn of 2018. The diurnal maxima were 4.5×106 cm−3 for OH radicals and 4.2×108 cm−3 for HO2 radicals (including an estimated interference of 23 %–28 % from RO2 radicals during the daytime), respectively. The state-of-the-art chemical mechanism underestimated the observed OH concentration, similar to the other warm-season campaigns in China. The OH underestimation was attributable to the missing OH sources, which can be explained by the X mechanism. Good agreement between the observed and modeled OH concentrations was achieved when an additional numerical X equivalent to 0.1 ppb NO concentrations was added into the base model. The isomerization mechanism of RO2 derived from isoprene contributed approximately 7 % to the missing OH production rate, and the oxidation of isoprene oxidation products (MACR and MVK) had no significant impact on the missing OH sources, demonstrating further exploration of unknown OH sources is necessary. A significant HO2 heterogeneous uptake was found in this study, with an effective uptake coefficient of 0.3. The model with the HO2 heterogeneous uptake can simultaneously reproduce the OH and HO2 concentrations when the amount of X changed from 0.1 to 0.25 ppb. The ROx primary production rate was dominated by ph...