Air quality expected to decrease over large parts of country early this week

A wide downturn in air quality is expected to affect most of China over the three days starting on Sunday, according to the Ministry of Ecology and Environment. This follows an elevation in air pollution nationally in January.

Northern provinces will be among the worst hit, with medium to heavy air pollution anticipated during the period, the ministry said on its Weibo account.

South China and southwestern areas will be less affected. Those regions were expected to see sporadic, light pollution on Sunday, and are forecast to have relatively clear skies until Tuesday, it said.

Light pollution also is forecast to affect East China starting Monday.

The China National Environmental Monitoring Center said the situation in the Beijing-Tianjin-Hebei region, which includes a number of steelmaking cities, will see short-lived progress on Wednesday, but another round of serious pollution will return and persist until the weekend.

In the Yangtze River Delta, which includes Shanghai, light or medium pollution is expected to affect the region's central and northern areas on Tuesday and Friday.

In the densely populated Pearl River Delta, which includes Guangzhou in Guangdong province, the air is expected to remain satisfactory thanks to rainfall and humidity.

The latest pollution comes after a bout of worsening air quality at the start of the year. Unpolluted days accounted for 67.6 percent of January in major Chinese cities, 3.5 percentage points lower than the same time period the previous year, according to the environmental ministry.

Beijing saw average PM2.5 levels of 52 micrograms per cubic meter, up 52.9 percent in January from a year earlier. Unpolluted days covered 77.4 percent of the month, down 6.5 percentage points year-on-year.

Cities in the Yangtze River Delta were no exception. The ministry said 41 cities in the region saw unpolluted days register at 56.4 percent in January, down by 1.1 percentage point from a year earlier. But the average concentration of PM2.5 was 72 micrograms per cubic meter, a 8.9 percent drop year-on-year.

Zhu Weiqun, a chemical engineering professor at Shandong University who studies fossil fuels and their impact on the air, said the January downturn is mainly due to a relaxation of pollution controls in production activities.

Industries like thermal power production, steelmaking and electrolytic aluminum, in which coal is widely used, contributed to the hike in air pollution, he said.

To tackle the problem in the short run, Zhu said more advanced pollution-fighting technologies are urgently needed.

"But in the long run, we need to develop new low-carbon emission industries to replace the outdated ones," he said.