Searching for the sources of particulate matter

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Award winner Alexander Vogel carries out research for better air quality

Particulate matter is a form of pollution whose sources are not all understood to this day. The very complex mixture is formed in the atmosphere from various gaseous precursor molecules. Identifying their sources and improving air quality is the goal of Alexander Vogel, Professor for Atmospheric Environmental Analytics at Goethe University. For his research projects, he received the Adolf Messer Foundation Award at a ceremony on 26th November. In honour of its 25th anniversary, the award amounts to € 50,000 this year.

According to estimates by the World Health Organisation, about 6.5 million people worldwide die prematurely due to air pollution, most of which can be attributed to particulate air pollu-tion. Contrary to popular opinion, most particulate matter doesn’t enter the atmosphere straight from tailpipes or power plants, but is formed in the atmosphere itself out of gaseous precursor molecules. This secondary particulate matter consists of the tiniest particles with an average diameter in the nanometre-range. These can penetrate deep into the lung and even enter the blood via the alveoles. An example for the formation of secondary particulate matter is the oxidation of nitrogen oxides from diesel engines: the resulting nitric acid mole-cules react with ammonia in the atmosphere to create ammonium nitrate.

The inorganic precursor molecules and their development to secondary particulate matter have been well investigated: nitrogen oxides from traffic and industry, sulphur dioxide from coal-burning power plants and ammonia from agriculture. But there are numerous organic molecules on top of this that also occur in nature, such as the terpenes emitted by spruce forests. Organic precursor molecules emitted by human activity in relation to the formation of secondary particulate matter is a highly topical research area. These precursor molecules and their interaction with inorganic trace gases have only been rudimentarily investigated to date. The clear identification of the products of these chemical reactions is made difficult by the fact that the molecules often have the same mass, although their structures are different.

While he was a postdoctoral fellow at the Paul Scherrer Institute in Switzerland, Alexander Vogel developed a method for creating a molecular fingerprint from atmospheric particular matter samples. By analysing them, he can determine the secondary formation mechanism. The molecular fingerprint of particulate matter samples from Los Angeles, for example, ex-hibits a high percentage of nitrogen-containing organic molecules. “This allows the assump-tion that a reduction in nitrogen oxide emissions would also lead to a reduction of organic particulate air pollution in urban areas,” Vogel explains.

However, to elucidate the formation mechanisms of individual substances, further analyses of atmospheric samples and specific laboratory experiments in which the formation of partic-ulate matter is simulated are necessary. By comparing field measurements with experiments, Alexander Vogel can already assign a portion of the signals in the real samples to certain processes and precursor molecules. Of the remaining unknowns, at least the molecular for-mula can be determined, so that potential sources and formation mechanisms can be investi-gated in further laboratory tests.

Alexander Vogel will now set up the experimental method he developed at the Paul Scherrer Institute at Goethe University. Among other things, he requires a machine for high perfor-mance liquid chromatography, which thanks to the Adolf Messer Foundation can now be acquired. His research approach has been met with great interest among environmental sci-ence master degree students. The measurements are due to begin at the start of 2019. Appli-cations for master’s and doctoral theses are already coming in.

The great relevance of this topic will also be emphasized in a symposium accompanying the award. With the title “Understanding particulate matter: A grand challenge of the 21st cen-tury?”, particulate matter measurement at the Frankfurt International Airport, smog in Chi-nese cities, and the health effects of particulate matter will be discussed.

Alexander Vogel, born in 1984, studied chemistry at Johannes Gutenberg-Universität Mainz. After receiving his Ph.D. (2014), research on the CLOUD experiment took him to the Euro-pean Organization for Nuclear Research CERN by Geneva and the Paul Scherrer Institute in Villigen, Switzerland. He has been a tenure-track professor for atmospheric environmental analysis at Goethe University since January 2018.

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Further information: Professor Alexander Vogel, Institute for Atmosphere and Environ-ment, Faculty of Geosciences, Riedberg Campus, Tel.: +49 69 798-40225, [email protected]

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Goethe University is a research-oriented university in the European financial centre Frankfurt The university was found-ed in 1914 through private funding, primarily from Jewish sponsors, and has since produced pioneering achievements in the areas of social sciences, sociology and economics, medicine, quantum physics, brain research, and labour law. It gained a unique level of autonomy on 1 January 2008 by returning to its historic roots as a “foundation university”. Today, it is among the top ten in external funding and among the top three largest universities in Germany, with three clusters of excellence in medicine, life sciences and the humanities. Together with the Technical University of Darmstadt and the University of Mainz, it acts as a partner of the inter-state strategic Rhine-Main University Alliance. Internet: http://www.uni-frankfurt.de

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