Inside a chimney that releases filtered air, part of a pilot project to reduce smog in Xi'an, China (IMAGE FROM DAVID CYRANOSKI/NATURE)

A 60-metre-high chimney stands in a sea of high-rise buildings in one of China’s most polluted cities. But instead of adding to Xi'an’s smog, this chimney is helping to clear the air. The outdoor air-purifying system, powered by the sun, filters out noxious particles and billows clean air into the skies. Chinese scientists who designed the prototype say that the system could significantly cut pollution in urban areas in China and elsewhere.

The technology has excited and intrigued researchers - especially in China, where air pollution is a daily challenge. Early results, which are yet to be published, are promising, says the project's leader Cao Junji, a chemist at the Chinese Academy of Sciences’ Key Laboratory of Aerosol Chemistry and Physics in Xi'an, central China. Other investigators include David Pui at the University of Minnesota in the United States and Tao Wenquan at Xi’an Jiaotong University, China.

"This is certainly a very interesting idea," says Donald Wuebbles, an atmospheric scientist at the University of Illinois at Urbana-Champaign, who has heard about the system but not seen it in action. "I am not aware of anyone else doing a project like this one."

The prototype, built with $2 million in funding from the provincial government, has also caught the attention of the president of the Chinese Academy of Sciences, Bai Chunli, who visited the site in February. Cao says Chinese leaders are eager for innovative solutions to air pollution because it creates such a widespread public-health problem. The Global Burden of Disease Study for 2015, a comprehensive effort to map the world's diseases, found that pollution contributed to 1.1 million premature deaths in China in that year alone.

Cao has submitted a proposal for another 300-metre tower in Xi'an. He is also negotiating proposals with Beijing and cities in Hebei and Henan.

Source：Nature