Decadal Transition of Summertime PM 2.5 -O 3 Coupling and Secondary Organic Aerosol Dominance in Northwest China

作者：Wei Zhou, Yang Liu, Siqi Zeng, Yunping Kan, Lirong Yang, Weihong Zhang, Weijie Wang, Zijun Zhang, Yan Li, Weiqi Xu, Yu‐Cheng Gu, Yaozong Wang, Zhengyan Zuo, Jie Li, Zifa Wang, Yele Sun · 年份：2025 · DOI：10.5194/egusphere-2025-5901 · 被引用次数：1 · 研究领域：Atmospheric chemistry and aerosols、Air Quality and Health Impacts、Atmospheric aerosols and clouds

Abstract. The Yinchuan metropolitan area in northwest China, situated between the Tengger and Ulan Buh Deserts, is influenced by both natural dust and anthropogenic emissions. However, the evolution of fine particulate matter (PM2.5) and its interaction with ozone (O3) under the region’s arid climate remain poorly understood. This study integrates decadal observations (2015–2025) with in-situ measurements using an Aerosol Chemical Speciation Monitor and a Vocus Proton Transfer Reaction Mass Spectrometry during summer 2025 to elucidate the changing PM2.5-O3 relationship and sources of organic aerosols. A pronounced shift was identified: Phase I (2015–2018) featured a rapid decline in PM2.5 accompanied by a sharp O3 increase, while Phase II (2019–2025) exhibited stabilized PM2.5 and plateaued O3, indicating reduced O3 sensitivity to particulate controls. The average non-refractory PM2.5 concentration (16.8 µg m-3) was significantly lower than in eastern Chinese megacities, with organics accounting for ~60 %. Positive matrix factorization resolved three organic aerosol factors, revealing dominant secondary organic aerosols (SOA, ~74 %) derived from prolonged photochemical aging. Volatile organic compound analysis showed that anthropogenic and biogenic precursors, including urban terpenes and aromatic oxidation products jointly contributed to SOA formation. Back-trajectory and potential source analyses indicated that Yinchuan’s summer air masses were mainly locally recirculated, ...