CGRER researchers improve predictability of extreme winter haze events


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Fine particulate pollution creates a winter haze over Hong Kong during December of 2009. (Jason Thien/flickr)
Jenna Ladd | December 27, 2016

Meng Gao and Gregory R. Carmichael have published research in Science Advances, an open-access peer-reviewed multidisciplinary scientific journal, that further explains extreme winter haze events in China.

Carmichael is a Karl Kammermeyer Professor of Chemical and Biochemical Engineering and co-director of the University of Iowa Center for Global and Regional Environmental Research (CGRER). Gao is a former University of Iowa postdoctoral research scholar that is currently a postdoctoral fellow at the John A. Paulson School of Engineering and Applied Sciences of Harvard University.

While working with Carmichael at the University of Iowa, Gao researched how well extreme winter haze pollution events in China could be predicted using state-of-the-art scientific models.

Sulfates are formed by reactions in the atmosphere or on aerosol surfaces. Prior to their recently published research, predicting rapid and heavily concentrated sulfate particulate formation was difficult. The report explains that previous models relied on photochemical oxidants, but because there is limited photochemistry activity during heavy haze events, they are not able to predict those events with the highest sulfate concentrations very well. Carmichael and Gao were only able to predict the correct number of sulfate particulates if they created an additional reaction pathway to create sulfate on particles.

The researchers note that winter haze poses health risks for more than 400 million people in the North China Plain. Sulfate is a major element in fine haze particles. This research follows record sulfate concentrations which led to the extreme winter haze event of 2013 in Beijing.

Carmichael explained, “By incorporating this new reaction pathway into our air quality model, our ability to predict winter time haze events has improved dramatically. Furthermore this more detailed understanding of how fine particles are formed will help guide more effective control measures.”

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