Most of major cities in China reported slightly improved air quality this week, according to the weekly air-quality report issued by the China Environmental Monitoring Center.

From November 12 to 18, windy condition and rainfall brought on by cold fronts moving southward, and weak, wet and hot air currents helped the diffusion and purification of pollutants over most of China, thus reducing air pollution in some cities.

But several cities in northwest and north China reported increased discharges of pollutants due to the increased use of coal for heating.

During this period, the air quality in six cities, namely, Haikou, Xiamen, Beihai, Nantong, Shantou and Fuzhou in southern China was fine, while 28 other cities, including Tianjin, Zhengzhou, Hangzhou, Wuhan, Xi'an, Shenyang, Chengdu, Nanjing, Qinhuangdao and Suzhou, reported good air quality.

Nevertheless, Beijing, Urumqi, Shijiazhuang, Shanghai, Taiyuan, Chongqing, Guiyang, Hohhot and Guangzhou were slightly polluted.

The air quality in Xining and Lanzhou in the northwest was polluted last week.

Moreover, Lanzhou, Hohhot, Xining and 12 other cities named suspended particles as the major pollutant.

Nitrogen oxide was the major pollutant in Beijing, Shanghai, Guangzhou, Wuhan, Jinan, Shenzhen and Zhuhai, whereas Chongqing, Changsha and Guiyang claimed sulfur dioxide as the major problem.