NOx emissions in China: Temporal variations, spatial patterns and reduction potentials

The Chinese government has already been aware of NOx emissions because they are mainly responsible for a complex air pollution situation in China. The main aim of this research is to disclose the temporal variations and the spatial patterns of NOx emissions of Chinese provinces, and then analyze reduction potentials. The main findings are as follows. (1) From 2006, the total NOx emissions in China continued to increase and then reached the summit in 2011, and began to decline until 2017. The two largest sources of NOx emission in China are industry and vehicle. (2) Most provinces with high NOx emissions are mainly concentrated on the North China Plain, but they have substantially reduced NOx emissions recently. However, from 2011 the share of NOx emissions from vehicles of all provinces sharply increased because of the ever-growing private vehicle consumption, indicating that the problem of vehicle emissions had become increasingly prominent (3) Per capita NOx emissions presented an inverted U-shaped curve, similar to the total NOx emissions. From the coefficients of variation and the kernel density estimates, we conclude that the differences in cross-province per capita NOx emissions narrowed notably after 2015. In other words, provinces with higher per capita NOx emissions have greater reduction potentials, and will catch up with provinces with lower per capita NOx emissions.