San Antonio, the second-most populous city in Texas and the seventh-most populous city in the United States (US), has been designated a marginal non-attainment area by the US Environmental Protection Agency with respect to the 2015 ozone (O₃) National Ambient Air Quality Standard. While stationary air quality monitoring sites are operated in the region by the Texas Commission on Environmental Quality (TCEQ), there are limited in situ field measurements for O₃ and its precursors in the urban core. To better understand O₃ dynamics in San Antonio, a suite of meteorological and gas instruments was deployed during May 2017. We incorporate field measurements from two campaign sites and one TCEQ stationary monitoring site into a zero-dimensional O₃ model to characterize the local formation and destruction rates of O₃, hydroxyl radical (OH) reactivity of volatile organic compounds (VOCs), O₃ production efficiency, and O₃ formation regime in the urban core and directly downwind of San Antonio. Upwind/downwind differences indicate the importance of photochemical processing of VOCs with carbon-carbon double bonds. San Antonio was mostly in a nitrogen oxide (NO_X)-sensitive regime throughout the daytime during the campaign period, with O₃ formation peaking at noon in the city center and early afternoon at the downwind region. Formaldehyde (HCHO), isoprene, and alkenes dominated VOC reactivity, with alkenes and isoprene from San Antonio's core (upwind) likely contributing to the downwind formation of HCHO and enhancing its OH reactivity. However, their direct impact on downwind O₃ production was not observed. Model results suggest further strengthening NO_X emission controls to decrease O₃ formation in San Antonio.

圣安东尼奥是德克萨斯州第二大人口城市和美国 (US) 第七大人口城市，已被美国环境保护署指定为关于 2015 年臭氧 (O ₃ ) 国家环境空气质量标准。虽然德克萨斯州环境质量委员会 (TCEQ) 在该地区运营了固定式空气质量监测站点，但对城市核心中O ₃及其前体的现场测量有限。为了更好地了解圣安东尼奥的O ₃动力学，2017 年 5 月部署了一套气象和气体仪器。我们将来自两个活动站点和一个 TCEQ 固定监测站点的现场测量合并到零维 O ₃模型来表征 O ₃的局部形成和破坏速率、挥发性有机化合物 (VOC) 的羟基自由基 (OH) 反应性、O ₃生产效率以及城市核心和圣安东尼奥正下风处的O ₃形成机制。上风/下风的差异表明光化学处理具有碳-碳双键的 VOC 的重要性。在竞选期间的整个白天，圣安东尼奥市大部分时间都处于氮氧化物 (NO _X ) 敏感状态，O ₃形成在中午在市中心和下午早些时候在下风区达到顶峰。甲醛 (HCHO)、异戊二烯和烯烃主导 VOC 反应性，来自圣安东尼奥核心（逆风）的烯烃和异戊二烯可能有助于 HCHO 的顺风形成并增强其 OH 反应性。然而，没有观察到它们对顺风O ₃生产的直接影响。模型结果表明进一步加强 NO _X排放控制以减少圣安东尼奥的O ₃形成。