Spatial and seasonal characteristics of particulate matter and gaseous pollution in China: Implications for control policy.

By employing the air pollution data including particular matter (PM) and gaseous pollutants (SO2, NO2, CO, and O3) measured over 130 cities in China from April 2014 to March 2015, the spatial and seasonal variations of air pollution are analyzed. The 9 representative regions including Beijing, Tianjin, and Hebei (BTH), Yangze River Delta (YRD), central China (CC), Sichuan Basin (SB), northeast China (NEC), northwest China (NWC), Pearl River Delta (PRD), Yungui Plateau (YP), and Tibet, are chose to quantify the conditions of PM and gaseous pollution. According to the magnitudes of PM2.5 from high to low, the regions are listed in sequence as BTH, CC, SB, YRD, NEC, NWC, PRD, YP, and Tibet. The spatial patters of gaseous pollutants except O3 are generally consistent with PM's. The CO maximum is found in BTH and NWC while the O3 maximum in YRD, PRD, and Tibet. The seasonal cycles of SO2 and NO2 are quite similar to that of PM, but the SO2 is overall higher than NO2 in winter over the northern China while the opposite is true over the southern China. The O3 concentrations are generally low in winter, but high in spring and summer due to active photochemical reaction when temperature is high. The percentage of haze days (daily PM2.5 exceeds NAAQS Grade II, i.e. 75  μg m-3) to the entire year is 45, 32 and 29%, respectively over BTH, CC, and SB, three most PM pollution regions during the study period. Although the most severe haze region occurs in BTH (139 days) from annual mean, the most severe winter in SB (54 days) owing to its basin landform and high air pollutant emissions. In contrary to PM pollution, gaseous pollution in China are overall quite trivial.