Science and technology: Air pollution: Blown away
Retired jet engines（退役喷射发动机） could help clear the smog that smothered big cities.To land at Indira Gandhi Airport is to descend from clear skies to brown ones.Delhi’s air is toxic.According to the World Health Organisation, India’s capital has the most polluted atmosphere of all the world’s big cities.
The government is trying to introduce rules that will curb emissions—allowing private cars to be driven only on alternate days（私家车单双数出行）, for example, and enforcing better emissions standards for all vehicles. （可以为写作做积累）
But implementing these ideas, even if that can be done successfully, will change things only slowly.A quick fix would help.
And Moshe Alamaro, a researcher at the Massachusetts Institute of Technology, thinks he has one.
His idea is to take a jet engine, put it next to one of India’s dirty coal-fired power plants, point its exhaust nozzle（排气喷嘴） at the sky and then switch it on.His hope is that the jet’s exhaust will disrupt a meteorological phenomenon known as “inversion”, in which a layer of warm air settles over cooler air, trapping it, and that the rising stream of exhaust will carry off the tiny particles of matter that smog is composed of.Inversion exacerbates air pollution in Delhi and in many other cities, from Los Angeles to Tehran.（逆流，作为地理常识，了解起来哦）
A particularly intense example caused the Great Smog of London in 1952, when four days of air pollution contributed to 12,000 deaths.（历史的教训）
Dr Alamaro thinks a jet engine could punch through the inversion layer to create a “virtual chimney” which would carry the trapped pollution above it, so that it could be dispersed in the wider atmosphere.He calculates that all the emissions from a gigawatt coal-fired power plant could be lifted away using a single engine with a nozzle speed of 460 metres a second.However, he has not calculated whether a jet engine could disrupt the inversion layer and allow the pollution to escape the city—so he is now going to test that hypothesis.
Within eight months, Dr Alamaro plans to put one of his updrafters next to a coal-fired power plant and monitor what happens using a fleet of drones.He is in discussions with Tata Group, a conglomerate with an electricity-generating arm, to run it next to one of the firm’s power stations.