Understanding the efficiency and variability of photochemical ozone (O₃) production from western wildfire plumes is important to accurately estimate their influence on North American air quality. A set of photochemical measurements were made from the NOAA Twin Otter research aircraft as a part of the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) experiment. We use a zero-dimensional (0-D) box model to investigate the chemistry driving O₃ production in modeled plumes. Modeled afternoon plumes reached a maximum O₃ mixing ratio of 140 ± 50 ppbv (average ± standard deviation) within 20 ± 10 min of emission compared to 76 ± 12 ppbv in 60 ± 30 min in evening plumes. Afternoon and evening maximum O₃ isopleths indicate that plumes were near their peak in NO_x efficiency. A radical budget describes the NO_x volatile - organic compound (VOC) sensitivities of these plumes. Afternoon plumes displayed a rapid transition from VOC-sensitive to NO_x-sensitive chemistry, driven by HO_x (=OH + HO₂) production from photolysis of nitrous acid (HONO) (48 ± 20% of primary HO_x) and formaldehyde (HCHO) (26 ± 9%) emitted directly from the fire. Evening plumes exhibit a slower transition from peak NO_x efficiency to VOC-sensitive O₃ production caused by a reduction in photolysis rates and fire emissions. HO_x production in evening plumes is controlled by HONO photolysis (53 ± 7%), HCHO photolysis (18 ± 9%), and alkene ozonolysis (17 ± 9%).

中文翻译：

---

西部野火羽流中臭氧光化学的变异性和时间依赖性

了解西部野火羽流产生的光化学臭氧 (O ₃ )的效率和可变性对于准确估计它们对北美空气质量的影响非常重要。作为火灾对区域到全球环境和空气质量的影响 (FIREX-AQ) 实验的一部分，从 NOAA 双水獭研究飞机上进行了一组光化学测量。我们使用零维 (0-D) 盒模型来研究驱动模拟羽流中O ₃产生的化学反应。模拟的下午羽流在排放的 20 ± 10 分钟内达到140 ± 50 ppbv（平均 ± 标准偏差）的最大 O ₃混合比，而傍晚羽流中的 76 ± 12 ppbv 在 60 ± 30 分钟内。下午和晚上最大 O ₃等值线表明羽流接近其 NO _x效率的峰值。激进预算描述了这些羽流的 NO _x挥发性有机化合物 (VOC) 敏感性。下午羽状显示从到NO VOC敏感的快速转变_X敏感的化学，由HO驱动_X（= OH + HO ₂）从亚硝酸的光解（HONO）生产（48±初级HO的20％_X）和甲醛（ HCHO) (26 ± 9%) 直接从火中排放。由于光解速率和火灾排放的降低，晚间羽流表现出从峰值 NO _x效率到 VOC 敏感的 O ₃生成的较慢过渡。过氧化_氢 晚羽的产生由 HONO 光解 (53 ± 7%)、HCHO 光解 (18 ± 9%) 和烯烃臭氧分解 (17 ± 9%) 控制。