Spatiotemporal dynamics of nitrogen dioxide pollution and urban development: Satellite observations over China, 2005–2016

Abstract

China experienced rapid urbanization and industrialization in recent years, which resulted in large increases of nitrogen dioxide (NO2), particularly in urban areas. We analyze the spatiotemporal variations of the vertical column densities (VCDs) of tropospheric NO2 with the level of urban development across China during the period 2005–2016. Nighttime light (NTL) data are applied as a proxy for urban development to investigate the relationship between NO2 pollution and urban development. Both NO2 column data and NTL data are observed by satellite measurements. The annual mean of NO2 VCDs is presented on a grid basis. The average annual variations of NO2 VCDs and NTL value are detected for all 341 prefectural cities. Two-thirds of the cities reached their peak NO2 pollution level around 2010–2012, and decreased afterward. About 10% of the western cities kept on increasing their NO2 levels until 2016. All cities are classified into four categories with respect to the average annual variations of NO2 /NTL in 2005–2010, and 2011–2016. Approximately 62% of the cities turned the average annual variations of NO2 /NTL from positive to negative. 19% of the cities are in the positive-positive category and 11% of the cities are in the negative-negative category. The remaining 8% of the cities changed their ratios from negative to positive. We summarize the national air pollution regulations, and our results show the effectiveness of the regulations for most eastern China cities. This work can help to design more efficient regional emission reduction policies with sustainable development.