Originally published on December 21, 2013
Chinese scientists are researching whether releasing a thick layer of cold gas formed by liquid nitrogen into Beijing's smoggy skies could help ameliorate the city's pollution problems, according to a report in the South China Morning Post.
Government researchers have proposed pumping liquid nitrogen into the air as a fine mist at least 10 metres above ground. The nitrogen would form a belt of cooler air roughly 20 metres thick that would act as a shield against air pollutants above. Dust and other pollutants in smog would be frozen, crystallized and fall to the ground. A smog-free zone would be created that and would last for several hours.
He Hui, a researcher at the government's Beijing Weather Modification Office, told the South China Morning Post that researchers used computer modeling to study how a number of chemical agents can could best help clean the air and found that the liquid nitrogen experiments proved be the most promising.
Wang Xinfeng, a researcher in atmospheric chemistry at Shandong University, told the South China Morning Post there were safety issues with using liquid nitrogen.
"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," Wang said.
"The liquid vaporised quickly when exposed to air and even a tiny spill on exposed skin or thin cloth could cause serious cold burns," he added.
Wang said that the cooling agent should be released no lower than five floors high and at a very low speed to avoid harming anyone on the ground.
He Hui also noted that small shifts in wind patterns could have unknown effects on the results of the computer simulations.
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