From San Francisco, at a meeting of the American Geophysical Union
Traffic-control measures can significantly reduce urban air pollution, a field study done in Beijing this summer indicates.
Beijing, a city of 15 million people and 3 million cars, has notoriously bad air, and it’s getting worse, says Tong Zhu, an atmospheric chemist at Peking University in Beijing. To assess how traffic-control measures might help curb pollution during this summer’s Olympics, researchers reduced the number of vehicles on the city’s roads from Aug. 17 through Aug. 20, a 4-day period that included two work days and one weekend. Pollution was measured by sensors on satellites, low-flying aircraft, and balloons, and at ground stations around the city.
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During the test, half of the region’s non-commercial, nongovernment vehicles—around 1.3 million—were kept off the roads from 6 a.m. to midnight each day. In general, reductions in pollution were larger on weekdays than on the weekend. Overall, daily reductions in nitrogen oxides in city air during the experiment ranged from 17 to 50 percent, and decreases in the concentrations of volatile organic chemicals, major contributors to the formation of ground-level ozone, ranged from 20 to 33 percent. Atmospheric concentrations of carbon dioxide consistently measured about 22 percent lower than they do on normal traffic days, Zhu adds.
Such reductions won’t meet the goals for air quality set by the government for the upcoming Olympics, Zhu and his colleagues note. Additional traffic control, as well as restrictions on construction, industries, and power plants in the region, will be necessary to reduce pollution the requisite amount.