Only 8 days of good air in city last month

Shanghai recorded only eight days last month when air quality was judged to be good or perfect, the city monitoring center said Sunday.

In each of the previous four Decembers, air quality reached these levels on around 20 days, reported the Shanghai Environmental Monitoring Center.

Meanwhile, a city academic has said that smog in southern regions of China is more hazardous than the haze found in the north of the country.

Zhuang Guozhun, a professor from Fudan University, said smog in Beijing mostly consists of natural dust particles.

In around 30 percent the main component is aluminosilicate — crystals that are poor at absorbing water.

But smog in areas in the Yangtze River Delta region is mainly composed of man-made pollutants — including ammonium salt, sulfate and nitrate — which can easily absorb water and expand rapidly.

For example, pollutant ammonium bisulfate can grow eight times in size, said Zhuang.

He concluded that with the same polluted conditions, it is easier for smog to form in southern regions than in northern ones.

And compared with natural dust particles, man-made pollutants are more dangerous as a large part of their components are heavy metal elements and toxic organics, said Zhaung

He highlighted vehicle emissions as a major source of pollution and urged authorities to limit the number of vehicles on the roads.