School of Ecology and Environment, Anhui Normal University, Wuhu, 241000, China; Center of Cooperative Innovation for Recovery and Reconstruction of Degraded Ecosystem in Wanjiang City Belt, Wuhu, 241000, China.
School of Ecology and Environment, Anhui Normal University, Wuhu, 241000, China.
Environ Pollut. 2024 Apr 15;347:123769. doi: 10.1016/j.envpol.2024.123769. Epub 2024 Mar 16.
In response to regional ozone (O) pollution, Chinese government has implemented air pollution control measures in recent years. Here, a case study was performed at an O-polluted city, Wuhu, in Yangtze River Delta region of China to investigate O variation trend and the relationship to its precursors after implementation of Clean Air Action Plan Phase II, which aims to reduce O pollution. The results showed that peak O concentration was effectively reduced since Clean Air Action Plan Phase II. Due to significant NOx reduction, O formation tended to shift from volatile organic compound (VOC)-limited regimes to NOx-limited regimes during 2018-2022. VOC/NOx ratios measured in 2022 revealed that peak O concentration tended to respond positively to NOx. Apart from high-O period, Wuhu was still in a VOC-limited regime. The relationship of maximum daily 8-h ozone average and NO followed a lognormal distribution with an inflection point at 20 μg m of NO, suggesting that Wuhu should conduct joint control of VOC and NOx with a focus on VOC reduction before the inflection point. Alkenes and aromatics were suggested to be preferentially controlled due to their higher ozone formation potentials. Using random forest meteorological normalization method, meteorology had a positive effect on O concentration in 2018, 2019 and 2022, but a negative effect in 2020 and 2021. The meteorology could explain 44.0 ± 19.1% of the O variation during 2018-2022. High temperature favors O production and O pollution occurred more easily when temperature was over 25 °C, while high relative humidity inhibits O generation and no O pollution was found at relative humidity above 70%. This study unveils some new insights into the trend of urban O pollution in Yangtze River Delta region since Clean Air Action Plan Phase II and the findings provide important references for formulating control strategies against O pollution.
针对区域性臭氧（O）污染问题，中国政府近年来实施了大气污染控制措施。在这里，我们选择长三角地区的臭氧污染城市芜湖进行了一项案例研究，以调查《清洁空气行动计划》（二期）实施后臭氧变化趋势及其前体物之间的关系，该计划旨在减少臭氧污染。结果表明，自《清洁空气行动计划》（二期）实施以来，臭氧峰值浓度得到了有效降低。由于氮氧化物（NOx）显著减少，2018-2022 年间，臭氧的形成倾向于从挥发性有机化合物（VOC）限制型向氮氧化物限制型转变。2022 年测量的 VOC/NOx 比值表明，臭氧峰值浓度与氮氧化物呈正相关。除了高臭氧期外，芜湖仍处于 VOC 限制型阶段。最大日 8 小时臭氧平均值与 NO 的关系呈对数正态分布，拐点在 20μg/m 的 NO 处，这表明芜湖应在拐点前对 VOC 和 NOx 进行联合控制，重点减少 VOC。由于较高的臭氧生成潜势，烯烃和芳烃被建议优先控制。使用随机森林气象标准化方法，气象对 2018 年、2019 年和 2022 年的臭氧浓度有积极影响，但对 2020 年和 2021 年的臭氧浓度有消极影响。气象条件可解释 2018-2022 年期间臭氧变化的 44.0±19.1%。高温有利于臭氧的生成，当温度超过 25℃时，臭氧污染更容易发生，而高相对湿度会抑制臭氧的生成，当相对湿度高于 70%时，不会发生臭氧污染。本研究揭示了《清洁空气行动计划》（二期）实施以来长三角地区城市臭氧污染的变化趋势，并为制定臭氧污染控制策略提供了重要参考。
