Shen Yang, Jiang Fei, Feng Shuzhuang, Xia Zheng, Zheng Yanhua, Lyu Xiaopu, Zhang LingYu, Lou Chenxi
Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210023, China.
Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210023, China; Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, China; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, China.
Sci Total Environ. 2023 Feb 1;858(Pt 1):159767. doi: 10.1016/j.scitotenv.2022.159767. Epub 2022 Oct 27.
Nitrogen dioxide (NO) is a key tropospheric O precursor. Since 2013, efforts to decrease air pollution in China have driven substantial declines in annual NO concentrations, whereas ozone (O) concentrations have increased. Based on nationwide NO observations and a regional air quality model (WRF-CMAQ), we analyzed trends in the diurnal difference (DD, the difference between nighttime and daytime concentrations) of NO concentrations across eastern China and in five national urban agglomerations (UAs) from 2014 to 2021, and explored the factors underlying such changes and the potential impacts on O pollution. We found that the observed DD of NO has increased in most cities and UAs, and that this trend can be primarily attributed to changes in anthropogenic emissions, based on comparison with DDs simulated with fixed anthropogenic emissions, which generally showed much weaker trends and little interannual variation. A sensitivity analysis using the WRF-CMAQ model was conducted to investigate the impact of a modified diurnal cycle of nitrogen oxides (NO) emissions on O concentrations. The result revealed that enhancing the DD of NO would increase O concentrations in the morning and the daily maximum 8-h O concentrations in the cities with high NO concentrations, as well as downwind areas of cities, indicating that greater DDs in NO is one of the reasons that have led to the enhanced China's O pollution in recent years.
二氧化氮（NO）是对流层臭氧的关键前体物。自2013年以来，中国为减少空气污染所做的努力使得年度NO浓度大幅下降，而臭氧（O₃）浓度却有所上升。基于全国范围内的NO观测数据以及区域空气质量模型（WRF-CMAQ），我们分析了2014年至2021年中国东部以及五个国家级城市群（UAs）中NO浓度的日变化差异（DD，夜间与白天浓度之差）趋势，并探究了此类变化背后的因素以及对O₃污染的潜在影响。我们发现，在大多数城市和城市群中，观测到的NO的DD有所增加，并且基于与固定人为排放情况下模拟的DD进行比较，这种趋势主要可归因于人为排放的变化，固定人为排放情况下的趋势通常要弱得多且年际变化很小。利用WRF-CMAQ模型进行了敏感性分析，以研究氮氧化物（NO）排放的修正日循环对O₃浓度的影响。结果表明，增强NO的DD会增加高NO浓度城市以及城市下风区域早晨的O₃浓度和每日最大8小时O₃浓度，这表明NO中更大的DD是近年来导致中国O₃污染加剧的原因之一。
