A government department in Xi'an, Shaanxi Province, has invested nearly one million yuan ($160,000) in a removable mist cannon designed to fight the city's dirty air, yet experts say the giant sprayer does little to reduce the density of PM2.5, the major contributor to the city's smog, the Beijing News reported on Monday.
The photo taken on May 9, 2014 shows a removable mist cannon which can reduce dust in air working on a street in Xi'an, Shaanxi province. [Photo/cnwest.com]
The Parks and Woods Bureau of the city's Xincheng district bought the machine from an environmental equipment manufacturer in Guangzhou with government financing of 900,000 yuan.
The 10-ton machine can spray water a distance of up to 600 meters and 70 meters high. The water goes up as a fine mist and sticks to dust to form larger particles, which fall to the surface under force of gravity.
Experts say that as a small-scale effort to dampen dust in Xi'an, the machine can help a little.
Pan Xiaochuan, an environmental expert at Peking University, said on Sunday that the machine's role in cleaning air pollution is temporary. Although the machine can reduce its surrounding pollutants within a short period of time after water is sprayed, its effects don't last long.
The machine is effective in controlling dust from construction sites, but it is useless in combating fine particles like PM2.5, according to a professor of atmospheric governance from Beijing.
"Fine particles like PM2.5 can form pollution layers which are over 200 meters above the ground," said the professor.
The major pollution sources in Xi'an are coal combustion, vehicle emissions and industrial releases, not dust, he added.