[A-AS04] Formation of Air Pollution and Its Interactions with Weather/Climate

[AAS04-P04] Spatiotemporal variations of recent NO₂ concentrations and anthropogenic and meteorological drivers over typical urban agglomerations in China

*Yang Shen¹, Fei Jiang¹ (1.Nanjing University)

Keywords:NO2, urban agglomeration, spatiotemporal pattern, WRF−CMAQ, quantitative impact

Nitrogen dioxide (NO₂) is an important pollution gas that can affect air quality and human health. In this study, spatiotemporal distribution of NO₂ concentrations throughout China, and specifically in twelve typical urban agglomerations, were statistically analyzed with ground−based NO₂ observations from June 2014 to May 2019. The WRF−CMAQ model were also applied to separate and quantify the emission−related and meteorology−related NO₂ variations. NO₂ concentration in Beijing−Tianjin−Hebei (BTH) urban agglomeration showed an upward trend in 2014−2015, and a downward trend after 2016, while NO₂ in Yangtze River Delta (YRD), Yangtze River Middle−Reach (YRMR) and Cheng−Yu (CY) urban agglomerations continued to decline until 2017. High NO₂ values were predominantly concentrated in urban agglomerations with high NOx emissions like BTH, Shandong Peninsula (SP), Central Plain (CP), Central Shaanxi (CS) and YRD urban agglomeration. The number of sites with NO₂ decreasing in 2018 accounts for 67.37% compared to 2015, especially in BTH and CP, with the decrease of more than 20 μg·m⁻³. High−high concentration centers of NO₂ pollution were observed in high NO₂ areas, while low−low aggregations were observed in the South and southwest of China. In general, anthropogenic emissions contributed dominantly to NO₂ variations, and the contribution in winter was greater than in summer. The reduction of emissions in the winter of 2018 led to emission−related NO₂ variations in YRD, YRMR, CY, and Pearl River Delta (PRD) urban agglomeration reaching −7.41, −9.15, −9.57, and −15.09 μg·m⁻³, respectively. While in the winter of BTH, meteorological influence on NO₂ was more obvious than that of other regions, leading variations of 4.42, 4.09, −9.77, and 5.99 μg·m⁻³, respectively between 2014 and 2018 in adjacent years. This study makes it possible to look into the differences in NO₂ concentrations among typical urban agglomerations and provide a more complete understanding of NO₂ exposures in China.