Scientists are studying the effects of pumping liquid nitrogen into Beijing’s atmosphere and whether it could help to reduce heavy air pollution in the capital, according to reports.
The government-backed research involves pumping the industrial coolant, nearly three times colder than dry ice, at least 10 meters above ground from large tanks.
According to SCMP:
Crystals form on the small particles of dust and other pollutants, which then fall to the ground. The belt of cooler air, less than 20 metres thick, also stops polluted air above reaching street level. The researchers said that during colder weather the belt, rich in vaporised liquid nitrogen, could remain hanging in the atmosphere for several hours.
He Hui, a researcher at the Beijing Weather Modification office, said that his team was given 250,000 yuan by the National Natural Science Foundation to carry out research on how various chemicals could affect the air. Other agencies, which he didn’t name, funded his liquid nitrogen experiments. He said that although it’s still in early stages of development, it could prove to be the most promising research.
“Our experiments showed that in an environment with temperatures below freezing point, liquid nitrogen outperformed all other agents, but in summer or autumn its effect was less obvious,” He said.
Previous methods of pollution-reduction used cloud seeding to create fake rain or snow to wash out air pollutants. China employed this practice before the opening of the Beijing Olympics in 2008 to ensure clear skies, and according to a document released by the China Meteorological Administration, authorities will permit the use of cloud seeding again in 2015.
He says that the deployment of chemicals is costly, however, and less effective in the wintertime when heavy smog is more prevalent.
Dr. Wang Xinfeng, a researcher out of Shandong University in Jinan, said in the SCMP report that while the use of liquid nitrogen to disperse smog is innovative, it can also be extremely dangerous.
“It is possible in theory to create a smog-free zone with liquid nitrogen and a shield against air pollutants with man-made cold, but even in laboratories we handle liquid nitrogen with care due to its extremely low temperature,” he said.