Intensive photochemical oxidation in the marine atmosphere: evidence from direct radical measurements

作者：Guoxian Zhang, Renzhi Hu, Pinhua Xie, Changjin Hu, Xiaoyan Liu, Liujun Zhong, Haotian Cai, Bo Zhu, Shi-Yong Xia, Xiaofeng Huang, Xin Li, Wenqing Liu · 发表于：Atmospheric chemistry and physics · 年份：2024 · DOI：10.5194/acp-24-1825-2024 · 被引用次数：15 · 研究领域：Atmospheric chemistry and aerosols、Atmospheric Ozone and Climate、Air Quality Monitoring and Forecasting

Abstract. Comprehensive observations of hydroxyl (OH) and hydroperoxy (HO2) radicals were conducted in October 2019 at a coastal continental site in the Pearl River Delta (YMK site, 22.55∘ N, 114.60∘ E). The daily maximum OH and HO2 concentrations were (4.7–9.5) × 106 and (4.2–8.1) × 108 cm−3, respectively. The synchronized air mass transport from the northern cities and the South China Sea exerted a time-varying influence on atmospheric oxidation. Under a typical ocean-atmosphere (OCM), reasonable measurement model agreement was achieved for both OH and HO2 using a 0-D chemical box model incorporating the regional atmospheric chemistry mechanism version 2-Leuven isoprene mechanism (RACM2-LIM1), with daily averages of 4.5 × 106 and 4.9 × 108 cm−3, respectively. Land mass (LAM) influence promoted more active photochemical processes, with daily averages of 7.1 × 106 and 5.2 × 108 cm−3 for OH and HO2, respectively. Heterogeneous uptake had certain effects on HOx chemistry, but the influence of the halogen mechanism was limited by NOx level. Intensive photochemistry occurred after precursor accumulation, allowing local net ozone production comparable with surrounding suburban environments (5.52 ppb h−1 during the LAM period). The rapid oxidation process was accompanied by a higher diurnal nitrous acid (HONO) concentration (> 400 ppt). After a sensitivity test, HONO-related chemistry elevated the ozone production rate by 33 % and 39 % during the LAM and OCM periods, respectivel...