Elucidating an Atmospheric Brown Carbon Species-Toward Supplanting Chemical Intuition with Exhaustive Enumeration and Machine Learning

Author(s)
Enrico Tapavicza, Guido Falk von Rudorff, David O. De Haan, Mario Contin, Christian George, Matthieu Riva, O. Anatole von Lilienfeld
Abstract

Brown carbon (BrC) is involved in atmospheric light absorption and climate forcing and can cause adverse health effects. Understanding the formation mechanisms and molecular structure of BrC is of key importance in developing strategies to control its environment and health impact. Structure determination of BrC is challenging, due to the lack of experiments providing molecular fingerprints and the sheer number of molecular candidates with identical mass. Suggestions based on chemical intuition are prone to errors due to the inherent bias. We present an unbiased algorithm, using graph-based molecule generation and machine learning, which can identify all molecular structures of compounds involved in biomass burning and the composition of BrC. We apply this algorithm to C12H12O7, a light-absorbing "test case" molecule identified in chamber experiments on the aqueous photooxidation of syringol, a prevalent marker in wood smoke. Of the 260 million molecular graphs, the algorithm leaves only 36,518 (0.01%) as viable candidates matching the spectrum. Although no unique molecular structure is obtained from only a chemical formula and a UV/vis absorption spectrum, we discuss further reduction strategies and their efficacy. With additional data, the method can potentially more rapidly identify isomers extracted from lab and field aerosol particles without introducing human bias.

Organisation(s)
Computational Materials Physics
External organisation(s)
Universität Basel, San Diego State University, Universidad de Buenos Aires, Université Claude-Bernard-Lyon-I, California State University, Long Beach
Journal
Environmental Science & Technology
Volume
55
Pages
8447-8457
No. of pages
11
ISSN
0013-936X
DOI
https://doi.org/10.1021/acs.est.1c00885
Publication date
06-2021
Peer reviewed
Yes
Austrian Fields of Science 2012
104010 Macromolecular chemistry, 102019 Machine learning
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/elucidating-an-atmospheric-brown-carbon-speciestoward-supplanting-chemical-intuition-with-exhaustive-enumeration-and-machine-learning(95283d2f-f87e-4959-9e6a-6e310193364b).html