• Wed
  • Dec 24, 2014
  • Updated: 11:29pm

Beijing air pollution

The Chinese capital has for many years suffered from serious air pollution. Primary sources of pollutants include exhaust emission from Beijing's more than five million motor vehicles, coal burning in neighbouring regions, dust storms from the north and local construction dust. A particularly severe smog engulfed the city for weeks in early 2013, elevating public awareness to unprecedented levels and prompting the government to roll out emergency measures. 


Liquid nitrogen may help to clean up Beijing smog, Chinese scientists say

Scientists say pumping the super-cold gas into the atmosphere had the best results in tests

PUBLISHED : Wednesday, 18 December, 2013, 11:43pm
UPDATED : Thursday, 19 December, 2013, 11:34am

Scientists are researching whether pumping super-cold gas into Beijing's atmosphere can help reduce air pollution in the capital.

He Hui, a researcher at the government's Beijing Weather Modification Office, said liquid nitrogen, an industrial coolant nearly three times as cold as dry ice, was promising as an anti-smog agent though it was in the early stages of development.

The government-funded research involves pumping the gas from large tanks into the air as a fine mist at least 10 metres above ground.

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.

Video: A view of Beijing's smog from atop the Forbidden City

Beijing Vice-Mayor Lin Keqing said this week that the city was investigating the use of technology to combat the capital's smog, but did not elaborate.

Conventional methods include seeding clouds with chemicals to create rain or snow to wash out air pollutants.

Cloud seeding was used ahead of the Beijing Olympics in 2008. But using aircraft to deploy enormous amounts of chemicals over the capital could prove costly and its efficiency is reduced in winter, a season with a higher frequency of smog in the north.

He's team was given 250,000 yuan (HK$317,000) by the National Natural Science Foundation last year to carry out computer simulations of how various chemical agents might help clean the air. Other agencies, which He declined to name, funded the liquid nitrogen experiments. This had proved the most promising research, he said.

"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. Other scientists have questioned whether this can be done safely.

Dr Wang Xinfeng, a researcher in atmospheric chemistry at Shandong University in Jinan , said the use of liquid nitrogen was unprecedented, innovative and backed by basic science, but the technology must be handled with care.

"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.

The liquid vaporised quickly when exposed to air and even a tiny spill on exposed skin or thin cloth could cause serious cold burns, Wang said.

If the agent was released at a point more than five floors high and at a very low speed, it would not cause harm to people on the ground, Wang said.

Another potential problem in using liquid nitrogen is wind.

"Small winds in different directions can alter our data quite significantly,'' said researcher He.

Fu Zuntao, a professor at Peking University, said the government had spent a lot on weather manipulation research that was often not publicised.


Related topics

For unlimited access to:

SCMP.com SCMP Tablet Edition SCMP Mobile Edition 10-year news archive



This article is now closed to comments

this is a great great idea !!! I will be starting my own company soon that will manufacture "in home" liquid nitrogen (or LN2) dispensers. It will be the approximate size of a dehumidifier and I hope to be selling them in shenzen or the ladies market here in mong kok. It will also have a dual function whereby you can make your own ice cream through a nozzle and container on the side that can be served up in minutes. Kids will love the vapour coming out of the nozzles and can provide countless hours of fun. I haven't really carried out an scientific study or possible hazards of this product but i think it should be ok !!!! now we can have good air and no pollution in home and china !!! yeeeeaaaaaa !!!
science with Chinese characteristics
What kind of government official idiot authorizes public funds to be spent on these kind of hair-brained schemes, when other well tested strategies offer much more promise? (Well tested - FGD, SCR, improved combustion, fuel improvement etc.)This is truly frightening. What you see in this is research organizations manipulating gullible politicians to further the interests of these research organizations with little hope for benefit for the public. This isn't just an environmental issue, this is a governance issue. Truly shameful.
Just how ignorant these scientists are. They don't stick to the fundamentals, just want a quick fix of doing something ecologically unknown. So bad, all the Chinese will have to swallow the bitter pill created by these morons.
More kook solutions, while proven technologies are ignored. Proven technologies are well put to use in every OECD country: better transportation fuel, for thermal power stations FGD for sulfur removal, SCR for NOx removal, bag houses and electrostatic precipitators for particulates, improved combustion. All of these China does do, but they underfund all of these and results are poor. Rather than do the obvious, China prefers to pursue magic bullet new technologies. Results are similarly obvious, just look at the quality of ambient air throughout China.
How silly!
Create a toxic soup in the air by allowing too many vehicles on their gridlocked roads and then try to "wash" the mess away constantly by expensive whitewashing, instead of removing the vehicles and preventing the toxic air from forming.
oh you naysayers
this is the same group of scientist that recently brought you their recent faked space walk conducted underwater
if they can do that , they can do this
I think they will have better luck with the invisibility cloak. Perhaps it can work on pollution. If people cannot see it, then they might not notice....ya think? I just wonder what disaster this idea is going to lead to?
This sounds like an accident waiting to happen. Liquid nitrogen is one of the more tricky substances to handle and these people are thinking about casually spraying it over the city?

First, SOMEONE is going to get burned. It doesn’t matter how high up they spray it. There’s just way too many variables and too many ways for something to go wrong.

Second, as liquid nitrogen is vaporized, it displaces the air around it and reduces the percentage of oxygen that is in the air. So rather than choking to death from the smog, people would be suffocating to death due to insufficient oxygen concentration in the air.
How about just pumping in lead and saving us the trouble down the road.



SCMP.com Account