A Missing Link in Haze Formation


Researchers have uncovered a key reaction that influences the growth of potentially harmful particles in the atmosphere.

Air-quality alerts often include the levels of particulate matter, small clumps of molecules in the lower atmosphere that can range in size from microscopic to visible. These particles can contribute to haze, clouds, and fog and also can pose a health risk, especially those at the smaller end of the spectrum. Particles known as PM10 and PM2.5, referring to clumps that are 2.5 to 10 micrometers in size, can be inhaled, potentially harming the heart and lungs.

This week, a group led by University of Pennsylvania scientists in collaboration with an international team report a new factor that affects particle formation in the atmosphere. Their analysis, published in the Proceedings of the National Academy of Sciences, found that alcohols such as methanol can reduce particle formation by consuming one of the process’s key ingredients, sulfur trioxide (SO3).

“Right now, we’re all concerned about PM2.5 and PM10 because these have some real air-quality and health consequences,” says Joseph S. Francisco, a corresponding author on the paper and an atmospheric chemist in Penn’s School of Arts and Sciences. “The question has been, How do you suppress the formation of these kinds of particles? This work actually gives some very important insight, for the first time, into how you can suppress particle growth.”

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Image via University of Pennsylvania