Seminar: “How can particles with a mass fraction of a few parts per billion have such huge health and climate effects?” by Neil Donahue

Particles concentrate molecules and allow them to have outsized effects once they are large enough to scatter light, activate clouds, and deliver toxicants to the lung. The story of their size and composition is however nuanced and complex. In many cases this size is 100 nm, where particles consist of more than 1 million molecules, most of which are formed via chemistry in the atmosphere. Often more than half of the molecules are organic, and their composition is incredibly rich. The story of how organic oxidation chemistry contributes to atmospheric particles is rich. Organic oxidation can lead to particle formation, and we measure particle formation and growth in the CLOUD experiment at CERN. We have studied organics arising from trees (terpenes) as well as those arising from human activity (aromatics), and found interactions among different organics through the free radicals that get formed during their oxidation.


photo of chimstry professor Neil DonahueNeil Donahue is the Thomas Lord University Professor of Chemistry in the Departments of Chemistry, Chemical Engineering, and Engineering and Public Policy at Carnegie Mellon University. He is a Pittsburgh native and has been at CMU since 2000. He was the founding director of the Center for Atmospheric Particle Studies (CAPS) and he now directs the Steinbrenner Institute for Environmental Education and Research, which represents all environmental research and education at CMU. CAPS is ranked among the world leaders in research addressing fundamental behavior of atmospheric aerosols as related to both air quality and climate. He has an undergraduate degree in Physics (Brown) and a doctorate in Meteorology (MIT). Before coming to CMU, he spent a decade in the laboratory of Jim Anderson at Harvard, where he honed his skills as a chemical physicist. He is a Fellow of the American Geophysical Union, editor of Atmospheric Chemistry and Physics, and associate editor of the Journal of Geophysical Research, Atmospheres. He has published more than 230 peer-reviewed journal articles, with more than 19,000 total citations and an “h-index” of 72. He has been recognized as a “highly-cited researcher,” in 2014 – 2019.

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