Regional source contributions to summertime ozone in the Yangtze River Delta

• Published in: Atmospheric environment (1994) Vol. 338; p. 120822
• Main Authors: Wang, Minghao, Ma, Jinlong, Tao, Chenliang, Gao, Yueqi, Zhang, Ruhan, Wang, Peng, Zhang, Hongliang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2024
• Subjects: CMAQ model; Ozone pollution; Regional transport; CMAQ model; Regional transport; Ozone pollution
• ISSN: 1352-2310
• DOI: 10.1016/j.atmosenv.2024.120822

Ozone (O3) pollution is increasing in the Yangtze River Delta (YRD), with significant influences from regional transport during pollution events. However, the specific contributions of different regions remain imprecisely quantified. This study estimated the regional contributions of eight regions to summer O3 in the YRD using the Community Multiscale Air Quality (CMAQ) model with a source-tagged photochemical mechanism. Non-background O3 is attributed to nitrogen oxides (NOX) and volatile organic compounds (VOCs) from different regions. Background O3 is the predominant contributor with average ratios of 75.0%, 65.3%, 64.8% and 63.0% for Shanghai, Nanjing, Hangzhou and the entire YRD, respectively. Locally formed O3 are 39.9, 42.0, 39.6, and 36.9 parts per billion (ppb) by volume in the above areas. North Zhejiang and south Jiangsu are the primary sources of heavy pollution episodes as the maximum daily 8-h average (MDA8) O3 concentrations in these regions increase the most. NOX is the predominant contributor to heavy pollution episodes with the maximum increment attributed to NOX (O3N) of 14.3 ppb, while VOCs only contribute to 2.1 ppb (O3V) in Jiangsu. Relative humidity is crucial in heavy pollution episodes while high temperature, low planetary boundary layer (PBL) height and the wind field are associated with regional transport. Diurnal variation underscores the importance of understanding O3 formation in the afternoon (12:00–16:00), which is essential for devising effective mitigation policies. •The regional source contributions of O3 in the YRD are determined for the Phase 2 of the CAA from 2018 to 2020.•Background O3 represents the predominant contributor to total O3.•Primary regional contributors to heavy O3 pollution in YRD are Jiangsu and Zhejiang provinces.•NOX serve as the predominant precursors in Zhejiang and Anhui while VOCs remain non-negligible in Jiangsu.•Relative humidity leads to heavy pollution episodes while wind field are associated with regional transport.