国产人人色I色婷婷综合久久中文字幕雪峰I奇米色777欧美一区二区I久热久热aV爽青青在线I国产av喷水I国产伦精品一区二区三区免.费I高潮av在线Iww欧美一级I91天天看I黄a在线91I九一无码中文字幕久久无码色…I丰满国产精品视频二区

   

Beijing car ban cut air pollutant by 40% - study

(Reuters)
Updated: 2007-05-01 09:45

WASHINGTON - When officials in Beijing kept about 800,000 cars off the road for three days last year, it cut the amount of nitrogen oxide air pollution almost instantly by about 40 percent, scientists reported on Monday.

The difference was apparent from space, observed by a NASA satellite, said Michael McElroy, a Harvard University professor of environmental studies and co-author of the report in Geophysical Research Letters.

Nitrogen oxides are key ingredients in ozone, which can exacerbate lung ailments such as asthma and emphysema.

Limiting the number of motor vehicles on the streets of the Chinese capital reduced nitrogen oxide levels dramatically during a Beijing summit in November, the scientists found.

Measured using satellite-based equipment, the change occurred almost as soon as the number of cars operating in Beijing dropped from the usual 2.8 million to about 2 million, he said, and nitrogen oxides rose back to normal levels shortly after the restrictions were lifted.

"I was frankly surprised that we were able to see it and that it was such a clean-cut experiment," McElroy said by telephone. "I thought it would be much fuzzier."

The experiment took place during a meeting between Chinese and African officials. Such vehicle bans are expected to be repeated this summer and then again next year in preparation for the Beijing Olympic Games, McElroy said.

"One of the big issues in the Olympics, a very serious problem, is the possibility that ozone levels during the Olympics will be very high," he said.

McElroy said Chinese officials would probably work hard to make sure Olympic visitors to Beijing will find a clean, modern city: "They don't want people arriving and coughing."

This might happen by banning all private cars from the city during the games, using buses and other means to ferry people about, he said. It is also possible that much of the Beijing-based industry, including chemical plants, will be shut down for the duration, according to McElroy.

There was some skepticism about whether the vehicle ban was responsible for the decline in ozone-forming oxides, since it coincided with a period of northwest winds that cleared the Beijing air, McElroy said.

Data collected by the NASA Aura spacecraft confirmed the correlation between the ban and the drop in nitrogen oxide.

Because ozone pollution is often regional, rather than local, McElroy said, emissions controls may be needed in the surrounding areas, as much as 620 miles (1,000 km) from Beijing.



Top China News  
Today's Top News  
Most Commented/Read Stories in 48 Hours