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Research Highlights

December 2011

Cutting Air Pollution Got Boost from Weather

Scientists compared emission controls versus weather during Beijing 2008 Olympic Games

Results: Pollution controls in Beijing and the adjacent provinces were only part of the air quality improvement story during the 2008 Summer Olympic Games. Scientists from Pacific Northwest National Laboratory and the Chinese Academy of Sciences found that rain at the beginning and wind during the games were at least as important as emission controls in reducing pollution particles. Their research suggests that to improve the air quality over major cities in China, emission control planning should focus on the regional scale instead of the local scale.

Why It Matters: With a population of more than 16 million, Beijing is one of the largest cities in the world, with an air quality problem to match. The 2008 Summer Olympic Games in Beijing presented a prime opportunity to study the effect of air pollution controls. In preparation for the Olympics, Beijing officials took strict measures in the city and surrounding regions to control air pollutants including particles with diameters less than 2.5 microns. Particles 2.5 microns and smaller are known to have serious health effects. By comparison, a human hair is typically 100 microns wide. This study improves the understanding of the effectiveness of pollution controls and how local and regional weather can affect air quality. This new information indicates ways decision-makers can plan effective strategies to improve air quality.

Methods: Scientists used WRF-Chem, a coupled meteorological-chemistry model, combined with observations for their research on emissions reduction from July 1-August 30, covering before and during the 16-day Olympic Games. Based on the budget analysis of aerosol pollutants, the team found that emission sources dropped by half in the week just before and during the Olympics. And while some pollution got washed out by rain or fell out of the sky, most of it got blown away by wind. Scientists considered pollution particles of 2.5 microns.

Pollution particles form smog that envelops construction of Beijing’s National Stadium, also known as the "Bird’s Nest." The stadium was home to many Olympic events. Photo courtesy of Ry Tweedie-Cullen.

Results of this study were published in the journal Atmospheric Chemistry and Physics. See PNNL news release, "Weather deserves medal for clean air during 2008 Olympics."

What's Next? The researchers will next examine the effect of pollution on other weather events and climate change in China. Aerosol pollutants are very small particles, and some researchers suspect they might be causing fog to form rather than rain because of the quantity of pollution particles in China.

Acknowledgments: This research was supported by the Department of Energy's Office of Science Scientific Discovery through Advanced Computing (SciDAC), the National Natural Science Foundation of China, and the Ministry of Environmental Protection of China. The work was performed by Ms. Yi Gao, formerly a visiting student of PNNL; Drs. Xiaohong Liu and Chun Zhao of PNNL; and Dr. M. Zhang of the Chinese Academy of Sciences in Beijing.

Reference: Gao Y, X Liu, C Zhao, and M Zhang. 2011. "Emission Controls Versus Meteorological Conditions in Determining Aerosol Concentrations in Beijing during the 2008 Olympic Games." Atmospheric Chemistry and Physics 11(23):12437-12451. DOI:0.5194/acp-11-12437-2011.

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