NOx in Chinese Megacities

In the past 30 years, China has undergone great economic improvements, the urbanization rate is increasing, megacities and city clusters are expanding, leading to the development of China's economy and society. However, the city expansion has resulted in a series of environmental problems, such as increasing energy consumption and consequently emission of pollutants, as well as deterioration in urban air quality. In spite of many measures taken by the Chinese government, air pollution from nitrogen oxides (NOx = NO + NO2) is still serious and the NOx concentration is increasing. This article analyses NOx pollution and its trends in Chinese megacities from three aspects, authoritative routine reports, campaign based research observations, and satellite observations. The article also discusses the main sources of NOx in Chinese Megacities. The discussion is based on a review of research papers on the China NOx emission inventory.