Spatiotemporal variations of tropospheric column nitrogen dioxide over Jing-Jin-Ji during the past decade

Of all anthropogenic pollutants, nitrogen dioxide (NO2) has the most negative effect on atmospheric chemistry. In this study, measurements of tropospheric column NO2 obtained from the ozone monitoring instrument (OMI) are used to investigate temporal and spatial dynamics of NO2. Temporal and spatial distributions of tropospheric NO2 concentrations obtained from OMI over the Beijing-Tianjin-Hebei (Jing-Jin-Ji) region from 2007 to 2016 are presented, and annual changes and trends in the seasonal cycle are shown. Annual amounts of NO2 are found to firstly increase then decrease, where after reaching a maximum in 2012 they begin a progressive yearly decline. NO2 shows significant cyclical seasonal characteristics over Jing-Jin-Ji, with maximum values in winter and minimum in summer. In addition, the spatial distribution is unbalanced, and Beijing-Tianjin-Tangshan and Shijiazhuang-Xingtai-Handan are found to be highly polluted areas. The many complex factors affecting variations in NO2 are analysed in this article, and the impact of meteorological factors and human activities are emphasized. It is considered that temperature and precipitation are natural factors influencing NO2 concentration but there is a stronger negative relationship between tropospheric column NO2 and temperature. Optimization of the energy structure is thus considered to be important and a reduction in energy consumption is required to control the concentration of pollutants. Coal combustion is a major anthropogenic factor in increasing NO2 concentrations, and there is a strong correlation between higher amounts of NO2 and coal consumption in the Jing-Jin-Ji region.