BEIJING, Dec. 4 (Xinhua) -- Some areas in northern China are likely to see another day of smog as the national observatory issued an orange alert for air pollution earlier Sunday.
Heavy smog will stay in some parts of Beijing, Tianjin, Hebei, Shandong, Henan and Shanxi from Sunday morning to Monday morning, according to the National Meteorological Center (NMC).
Central and southern Hebei will see PM2.5 density higher than 500 micrograms per cubic meter in air with visibility reduced to less than 200 meters, said the NMC.
The NMC said a cold front will help disperse the smog later Monday.
China has a four-tier color-coded system for severe weather, with red being the most serious, followed by orange, yellow and blue.
An orange alert means heavy pollution -- PM2.5 density of higher than 150 micrograms per cubic meter of air -- for three consecutive days.
When the alert is in force, outdoor activities in schools will be canceled and construction projects suspended.
In Beijing, kindergartens, primary and middle schools have been advised to reduce outdoor activities, and large vehicles such as garbage trucks have been forced to lay by since Friday.
Hebei also closed several highway sections to reduce traffic.
After experiencing frequent bouts of smog, the Chinese public has become increasingly sensitive to the health hazard. To address public concerns, the government aims to cut the density of inhalable particulate matter by at least 10 percent in major cities by 2017.
The NMC also issued an alert for heavy fog in parts of Beijing, Tianjin, Hebei, Sichuan, Chongqing and Guizhou with visibility possibly reaching less than 200 meters.