Beijing reaches annual "blue sky days" target

BEIJING, Dec. 17 (Xinhua) -- As of Sunday, Beijing has enjoyed 274 days of "blue sky" in 2011, fulfilling its annual target ahead of schedule, an official with Beijing's Municipal Environmental Protection Bureau said Sudnay.

Beijing has seen an overall decline in the concentration of various pollutants in 2011, said Zhuang Zhidong, deputy director of the bureau.

The PM10, or particular matter under 10 micrometers, decreased to 114 microgrammes per cubic meter this year, the lowest in four years, according to the bureau.

The overall air quality of Beijing was better than last year, with 22 more days of grade I air quality than were recorded in 2010, Zhuang said.

Beijing uses a five-grade classification of air quality on the basis of pollution indices, with grade I being the best and grade V the worst. Days with grade I or II air quality are considered "blue sky days."

However, Beijing also experienced several days of poor air quality as a result of bad weather conditions. Factors such as weaker winds and a rise in humidity are unsuitable for the dispersal of atmospheric pollutants, according to the bureau.