More than three billion yuan (about $451 million) has been invested this year to tackle the air pollution in Urumqi. And in the next three to five years, another 16.8 billion yuan will pour in, Jierla Yishamuding, mayor of Urumqi, Xinjiang's capital city, said on Oct. 19.

Located in central Xinjiang, Urumqi has long been known for its wintertime air pollution. Jierla cited several reasons for pollution. The city is surrounded by mountains, and its low altitude and terrain hinder the air flow, which is a major cause of smog. Additionally, most of the city's heating boilers still burn coal, which release dirty fumes and dust.

Twenty key projects related to air-pollution control are being implemented in the city, and 156 boilers have been shut down this year while a centralized heating system will be pushed forward. Urumqi plans to switch heating facilities from coal to gas. It's also planning to move polluting industries to the city's outskirts.