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_2.5 and O₃ 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 (PM₁₀, PM_2.5, SO₂, NO_X, and O₃). The results show that the reduced emissions have improved the air quality in China. However, the Chinese National Ambient Air Quality Standard (CNAAQS) for PM₁₀ and PM_2.5 still be exceeded in many cities of China in 2015. A total of 77.5% (for PM_2.5) and 65.4% (for PM₁₀) of the monitoring cities were found to be exceeded CNAAQS. The average annual O₃ concentration was increasing during 2013-2015, and 16% of the total cities in 2015 did not meet the CNAAQS, indicating that O₃ pollution should be paid more attention. For NO₂ and SO₂, the exceedances of CNAAQS are rare. PM_2.5, PM₁₀, and SO₂ concentrations are higher in northern than in southern regions. High NO₂ occurred in Beijing-Tianjin-Hebei and Yangtze River delta region. Secondary particles formation and motor vehicle exhaust were the main sources of PM_2.5 in megacities. Dust was the main source for PM₁₀. The formation of O₃ is VOC-limited in urban areas of China and NO_X-limited in nonurban areas.