Beijing's first smog red alert has helped to prevent air pollution from worsening, environmental experts said on Wednesday.

The capital has been on red alert since Tuesday morning, and the warning is due to be lifted at noon on Thursday.

The alert helped to cut concentrations of PM2.5 by 10 percent on Tuesday, said Cheng Shuiyuan, head of the College of Environmental and Energy Engineering at Beijing University of Technology.

His team has been carrying out a simulation experiment to assess the effects of the emergency measures taken by the government in response to the red alert.

The China Research Academy of Environmental Sciences, under the Ministry of Environmental Protection, also conducted real-time analysis on sources of air pollutants for the first time.

Chai Fahe, deputy head of the academy, said the amount of nitrates - a main pollutant from vehicle exhaust - was halved on Tuesday thanks to the red alert.

He said this showed that restrictions on the number of vehicles allowed on the roads had worked, adding that other efforts such as reducing coal consumption have also helped to reduce emissions. Under the red alert, vehicles are allowed on the roads on alternate days based on odd and even license plate numbers.

Other measures taken include shutting down industrial operations and closing schools and kindergartens.

At 5 pm on Wednesday, the reading for PM2.5 in Beijing was 233, still four times more than the safety level, the municipal environmental watchdog said. The smog is expected to persist until noon on Thursday when wind is forecast to disperse it.

Wang Zifa, a researcher at the Institute of Atmospheric Physics at the Chinese Academy of Sciences, said the emergency measures had cut pollution.

During the smog alert, 70 percent of pollutants had been generated from Beijing and surrounding areas, he said.

The capital has suspended or stopped production at about 2,100 polluting companies and outdoor work has been halted at 3,500 construction sites.

In inspections at 528 polluting companies and construction sites on Wednesday, the Beijing environmental watchdog found 37 violating the restrictions.

On Tuesday, the smog blanketed at least six provinces and municipalities, covering more than 840,000 square kilometers, the Ministry of Environmental Protection said.

In addition to Beijing, Tianjin and 29 cities in Hebei, Shandong and Shanxi provinces have issued different levels of alert aimed at curbing the smog.

This has reduced coal consumption and vehicle use in many cities.

zhengjinran@chinadaily.com.cn

(China Daily USA 12/10/2015 page1)