Exploring the fate and impact of atmospheric radicals and reactive intermediates
Atmospheric radical control the removal of many natural and man-made compounds. This process results in formation of secondary pollutants, such as ozone and particulate matter, which have large impacts on climate and human health. Despite the key importance of radical species in the atmosphere, their detection and quantification are very challenging specifically due to their high reactivity. Our goal is to study the fate of atmospheric radicals under controlled conditions in laboratory and chamber experiments.
Current and recent research on atmospheric radicals
(1) We conducted a series of chamber experiments studying photooxidation of aromatic compounds in close collaboration with the Kroll group at MIT and Aerodyne Research. We studied the fate of bicyclic peroxy radicals (BPRs) under urban-relevant high-NOx conditions. We showed that even under those conditions BPRs can undergo unimolecular reactions (so called autooxidation pathway) that lead to formation of highly oxygenated molecules (HOMs) and can effectively contribute to secondary aerosol formation and therefore adversely affect public health and climate (Zaytsev et al., 2019).
Oxidation pathways of bicyclic peroxy radicals (BPR, shown in yellow) in the OH-initiated oxidation of 1,2,4-trimethylbenzene.
(2) Inspired by the wide usage of spin trapping and chemical derivatization (CD) to measure radicals in biological systems, we are currently exploring how these agents could be used to detect atmospheric radicals and reactive intermediates. We show that spin traps and CD agents are highly reactive towards atmospheric radicals and form stable adducts with them that can be detected using chemical ionization mass spectrometry. This method allows to suppress radical secondary reactions and cycling, which ensures that measurements are not biased by chemical interferences.
This schematic demonstrates the principles of radical detection using spin trapping combined with chemical ionization mass spectrometry (CIMS).
For more information please contact Alex Zaytsev at zaytsev (at) g.harvard.edu