Beijing air sets Olympic gold standard

CORNELL (US)—Aggressive efforts by the Chinese government to curtail traffic, increase emission standards, and halt construction led to cleaner air in Beijing during the 2008 Olympics, a new study finds.

“We hope our study can help or advise local regulators and policymakers to adopt long-term sustainable emission controls to improve air quality,” says Max Zhang, assistant professor of mechanical and aerospace engineering at Cornell University. “That’s our mission.”


Published online July 11 in the journal Atmospheric Environment, the study was based on air quality readings before, during, and after the Olympics and indicates that regulating traffic density and encouraging public transportation can have a significant impact on local air quality.

Leading up to the Olympics, the Chinese government put into place several regulations aimed at improving air quality, including barring more than 300,000 heavy-emission vehicles—mostly trucks—from the roads. They also allowed people to drive only on certain days based on license plate numbers, halted construction, and decreased the use of coal in favor of natural gas.

In 2007 and 2008, the researchers collected air quality data from equipment installed at two elevations in the heart of Beijing. They also tracked emissions from vehicles in different areas of the city by following randomly selected cars and trucks in a minivan equipped with instruments for detecting carbon particles, including carbon monoxide, carbon dioxide, and black carbon or soot.

Researchers found that diesel trucks are a major source of black carbon pollution, which is significantly greater at ground level than at higher elevations. Black carbon is not only harmful to the lungs, but is also known to be a global warming compound, Zhang says.

Analysis of the data showed car emissions of black carbon were down 33 percent in 2008 compared with their 2007 readings, carbon dioxide decreased 47 percent, and ultrafine carbon-based particles—those that measure less than 100 nanometers—decreased 78 percent.

Zhang and his team believe the sharp drops were most likely due to a new emission standard implemented in Beijing in 2008, in which all new registered vehicles as well as gasoline and diesel fuel engines were required to achieve emissions standards equivalent to European Union regulations.

A similar standard was mandated starting in June 2008 for 20,000 buses and 66,000 taxies. The improved fuel quality probably enhanced the performance of engines and catalytic converters, the researchers report.

“We are showing what the city can do if they are determined to improve air quality,” Zhang says.

The study was funded by the U.S. Environmental Protection Agency and Cornell’s Jeffrey Sean Lehman Fund for Scholarly Exchange with China.

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