LANZHOU, Feb. 11-- Lanzhou, capital of northwest China's Gansu Province reported 252 days of excellent or good air quality last year, 59 days more than in 2013, according to the city's environmental protection bureau.

Lanzhou is situated in the Yellow River valley and surrounded by mountains, which hinders dispersion of pollutants and dustfall. Pollution in the city is especially worse in winter as a result of burning wood and coal.

Once listed as one of China's top 10 most polluted cities, Lanzhou even disappeared from satellite photos.

But things have changed for the better as measures aim to curb air pollution took effect.

Since the end of 2011, local government started to upgrade all the 150,000 coal-fired boilers in the city, and has removed 1,286 of them, cutting 4.79 million tonnes of carbon emission. Residents now use anthracite with government subsidies.

The three thermal power plants in urban area have cut their emissions by using less, good quality coal and checkpoints have been set up around the city to prevent inferior coal from entering.

Annual coal consumption in the city has been reduced to 6.2 million tonnes, nearly 4 million tonnes less than three years ago.

Sprinklers have been used to control smog and dust, which local residents say made day looks as dark as night.

According the Chinese Academy of Sciences, water spraying can reduce PM10 from 200 micrograms per cubic meter to 120 micrograms per cubic meter.

"In the past, I could rarely see the surrounding mountains clearly due to the heavy pollution, but now people can see the mountains clearly from the city proper and, standing on top of the mountain, they can clearly see the streetscape in downtown area," said 62-year-old Zhang Yucun, a native of Lanzhou.

Lanzhou was awarded "Reform Progress Prize" at the United Nations Climate Change Conference in Paris in 2015.