According to the Ministry of Environmental Protection, since Dec. 5, due to the large quantity of pollutants discharged and the unfavorable climate conditions, Beijing and its neighboring regions have seen severe smog.

To better understand the cause, developing trend of the heavy pollution and the effect of the red alert measures in Beijing, a research team constituted by experts from Chinese Academy of Sciences, Tsinghua University, Peking University, China National Environmental Monitoring Center and other top research institutions has conducted a study on the smog this week. 

Experts believe that the heavy air pollution this week is the result of the joint action of unfavorable climate condition and multiple sources of pollution.

Analysis on monitoring data shows that the sources of the pollutants of this week's smog are, in order of quantity, coal combustion, vehicle emission, industrial sources, fugitive dust and other sources. Pollutants from coal combustion mainly came from scattered burning of raw coal and emissions from small and medium-sized boilers. The vehicle emission includes gasoline car emission and diesel engine emission. The industrial sources include the steel manufacturing, petrochemical engineering, building material production and other industrial productions in the region. In terms of the city of Beijing, the main sources of pollutants are scattered burning of raw coal and vehicle emission. 

"Data show that after Beijing implemented the air pollution red alert measures, the emission reduction averaged about 30 percent. If we didn't take such measures, the PM2.5 density would be 10 percent higher," said Cheng Shuiyuan, professor of Environment and Energy Engineering School of Beijing University of Technology. Monitoring data show that the emergency measures have obvious effect on preventing the smog from going worse.