Characteristics of Major Air Pollutants in China.

Following the rapid development of China's economy, air pollution has become more and more serious. Air pollution in China presents complex pollution characterized by high PM and O concentration. This study presents an overview of the status of air quality and emission in China and discusses the temporal and spatial distribution of major pollutants (PM, PM, SO, NO, and O). The results show that the reduced emissions have improved the air quality in China. However, the Chinese National Ambient Air Quality Standard (CNAAQS) for PM and PM still be exceeded in many cities of China in 2015. A total of 77.5% (for PM) and 65.4% (for PM) of the monitoring cities were found to be exceeded CNAAQS. The average annual O concentration was increasing during 2013-2015, and 16% of the total cities in 2015 did not meet the CNAAQS, indicating that O pollution should be paid more attention. For NO and SO, the exceedances of CNAAQS are rare. PM, PM, and SO concentrations are higher in northern than in southern regions. High NO occurred in Beijing-Tianjin-Hebei and Yangtze River delta region. Secondary particles formation and motor vehicle exhaust were the main sources of PM in megacities. Dust was the main source for PM. The formation of O is VOC-limited in urban areas of China and NO-limited in nonurban areas.