The smog enveloping parts of the mainland, the severest so far this winter, will persist in eastern China until today, according to the National Meteorological Centre.
A cold front was expected to sweep across central and east parts of China starting last night, which would gradually clear the smog that has lingered in parts of the country for more than a week, the centre said yesterday.
Smog in Beijing and elsewhere in the north started to disperse yesterday. Revising the smog alert from "orange" down to "yellow" in the afternoon, the centre said haze would remain severe in parts of Zhejiang , Jiangsu , Anhui , Shandong , Henan and Hebei provinces until this afternoon.
The air quality indexes in nearly 80 cities yesterday were above 200, meaning the air was "heavily" or "severely" polluted.
Video: Eastern areas of China cloaked in smog
The country's three city clusters around Beijing, Shanghai and Guangzhou have traditionally been the major victims of episodes of persistent smog. But the pattern has changed, with other inland cities being affected in provinces including Anhui, Hubei , Hunan and Jiangxi , according to Professor Chai Fahe, vice-president of the Chinese Research Academy of Environmental Sciences.
"Locally generated emissions remain the prime cause of the severe smog, but it is exacerbated by the static atmospheric condition that traps the pollutants," Chai said.
The smog in Jiangsu and Zhejiang combined with thick fog yesterday morning. Visibility was reduced to less than 50 metres in the provincial capital of Nanjing and the city maintained its red alert for pollution for the fifth consecutive day.
About 250 flights from Hangzhou , Nanjing and Zhengzhou were delayed or cancelled, according to local media reports. Highways were also forced to shut down.
In Beijing, strong northern winds began to blow away some pollutants. Also, Shanghai's meteorological centre lifted its pollution alert, as the smog "has considerably lessened", although the air quality was still rated as "medium polluted".
The city has been among the hardest hit in the recent week by pollution, with the concentration of PM2.5 particulate matter, or tiny particles in the air that are the most hazardous to health, going beyond the index. The Ministry of Environmental Protection said the smog was the result of unfavourable weather conditions, motor vehicle exhausts and coal consumption for heating.
But most cities are hoping to devise a detailed break down of their local pollution sources, which may still take months to produce, if not years, Chai said.
"The breakdown is different from region to region and from time to time. Though we do know the general pollution sources, a more detailed breakdown will make pollution treatment measures more efficient."
For instance, the burning of corn stalks in the Yangtze River Delta was blamed by some as a major cause of this round of smog, but there is no detailed data available yet of how much the practice has contributed.
"We must face up to the realities," said Yan Naiqiang, a professor of environmental science at Shanghai Jiao Tong University. "The treatment of smog will be a long battle."