Javed Zeeshan, Bilal Muhammad, Qiu Zhongfeng, Li Guanlin, Sandhu Osama, Mehmood Khalid, Wang Yu, Ali Md Arfan, Liu Cheng, Wang Yuhang, Xue Ruibin, Du Daolin, Zheng Xiaojun
Institute of Environment and Ecology, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013 China.
School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing, 210044 China.
Environ Sci Eur. 2022;34(1):86. doi: 10.1186/s12302-022-00668-2. Epub 2022 Sep 8.
The spatiotemporal variation of observed trace gases (NO, SO, O) and particulate matter (PM, PM) were investigated over cities of Yangtze River Delta (YRD) region including Nanjing, Hefei, Shanghai and Hangzhou. Furthermore, the characteristics of different pollution episodes, i.e., haze events (visibility < 7 km, relative humidity < 80%, and PM > 40 µg/m) and complex pollution episodes (PM > 35 µg/m and O > 160 µg/m) were studied over the cities of the YRD region. The impact of China clean air action plan on concentration of aerosols and trace gases is examined. The impacts of trans-boundary pollution and different meteorological conditions were also examined.
The highest annual mean concentrations of PM, PM, NO and O were found for 2019 over all the cities. The annual mean concentrations of PM, PM, and NO showed continuous declines from 2019 to 2021 due to emission control measures and implementation of the Clean Air Action plan over all the cities of the YRD region. The annual mean O levels showed a decline in 2020 over all the cities of YRD region, which is unprecedented since the beginning of the China's National environmental monitoring program since 2013. However, a slight increase in annual O was observed in 2021. The highest overall means of PM, PM, SO, and NO were observed over Hefei, whereas the highest O levels were found in Nanjing. Despite the strict control measures, PM and PM concentrations exceeded the Grade-1 National Ambient Air Quality Standards (NAAQS) and WHO (World Health Organization) guidelines over all the cities of the YRD region. The number of haze days was higher in Hefei and Nanjing, whereas the complex pollution episodes or concurrent occurrence of O and PM pollution days were higher in Hangzhou and Shanghai.The in situ data for SO and NO showed strong correlation with Tropospheric Monitoring Instrument (TROPOMI) satellite data.
Despite the observed reductions in primary pollutants concentrations, the secondary pollutants formation is still a concern for major metropolises. The increase in temperature and lower relative humidity favors the accumulation of O, while low temperature, low wind speeds and lower relative humidity favor the accumulation of primary pollutants. This study depicts different air pollution problems for different cities inside a region. Therefore, there is a dire need to continuous monitoring and analysis of air quality parameters and design city-specific policies and action plans to effectively deal with the metropolitan pollution.
The online version contains supplementary material available at 10.1186/s12302-022-00668-2.
对长江三角洲（YRD）地区包括南京、合肥、上海和杭州等城市的观测痕量气体（NO、SO、O）和颗粒物（PM、PM）的时空变化进行了研究。此外，还研究了长江三角洲地区不同城市的不同污染事件特征，即霾事件（能见度<7公里、相对湿度<80%且PM>40μg/m）和复合污染事件（PM>35μg/m且O>160μg/m）。研究了中国清洁空气行动计划对气溶胶和痕量气体浓度的影响。还研究了跨界污染和不同气象条件的影响。
2019年所有城市的PM、PM、NO和O的年平均浓度最高。由于长江三角洲地区所有城市实施了排放控制措施和清洁空气行动计划，PM、PM和NO的年平均浓度从2019年到2021年持续下降。长江三角洲地区所有城市的年平均O水平在2020年有所下降，这是自2013年中国国家环境监测计划开始以来前所未有的。然而，2021年观测到年平均O略有增加。合肥的PM、PM、SO和NO的总体平均值最高，而南京O水平最高。尽管采取了严格的控制措施，但长江三角洲地区所有城市的PM和PM浓度均超过了国家环境空气质量一级标准（NAAQS）和世界卫生组织（WHO）的指导方针。合肥和南京的霾天数较多，而杭州和上海的复合污染事件或O和PM污染天数同时出现的情况较多。SO和NO的现场数据与对流层监测仪器（TROPOMI）卫星数据显示出很强的相关性。
尽管观测到一次污染物浓度有所降低，但二次污染物的形成仍然是主要大都市关注的问题。温度升高和相对湿度降低有利于O的积累，而低温、低风速和相对湿度降低有利于一次污染物的积累。本研究描述了一个地区内不同城市的不同空气污染问题。因此，迫切需要持续监测和分析空气质量参数，并制定针对特定城市的政策和行动计划，以有效应对大都市污染。
在线版本包含可在10.1186/s12302-022-00668-2获取的补充材料。
