Seasonal and long-term trends of sulfate, nitrate, and ammonium in PM 2.5 in Beijing: implication for air pollution control

Particulate matter pollution in Beijing is a serious environmental problem. In response to this, the Beijing government has implemented comprehensive emission reduction measures in recent years. To assess the effectiveness of these measures, the seasonal and long-term trends in chemical compositions of PM 2.5 in Beijing have been studied based on daily samples collected from July 2015 to April 2016 and literature investigation (2000–2014). Results show that the concentrations of sulfate, nitrate, and ammonium in PM 2.5 have significant seasonal variations, which are related to the changes in meteorological conditions and emission intensities. In addition, the long-term data display that the concentrations of sulfate, nitrate, and ammonium have significantly decreased between 2013 and 2016, which are consistent with the reduction in PM 2.5 levels (~ 11.2 μg/m 3 per year). The declines could not be interpreted by the meteorological factors. It suggests that the air pollution control measures in Beijing (2013–2016), especially the decreasing consumption of coal, can effectively decrease the mass concentration of fine particles. To further improve the air quality, similar measures should be adopted in the areas around Beijing. These air pollution control measures taken in Beijing can provide invaluable guidance for mega-cities in China and other developing countries to decrease their PM 2.5 concentration and reduce health risk from particulate pollution.