Nitrogen-containing organic carbon (NOC) in atmospheric particles is an important class of brown carbon (BrC). Redox active NOC like aminophenols received little attention in their ability to form BrC. Here we show that iron can catalyze dark oxidative oligomerization of o- and p-aminophenols under simulated aerosol and cloud conditions (pH 1–7, and ionic strength 0.01–1 M). Homogeneous aqueous phase reactions were conducted using soluble Fe(III), where particle growth/agglomeration were monitored using dynamic light scattering. Mass yield experiments of insoluble soot-like dark brown to black particles were as high as 40%. Hygroscopicity growth factors (κ) of these insoluble products under sub- and super-saturated conditions ranged from 0.4–0.6, higher than that of levoglucosan, a prominent proxy for biomass burning organic aerosol (BBOA). Soluble products analyzed using chromatography and mass spectrometry revealed the formation of ring coupling products of o- and p-aminophenols and their primary oxidation products. Heterogeneous reactions of aminophenol were also conducted using Arizona Test Dust (AZTD) under simulated aging conditions, and showed clear changes to optical properties, morphology, mixing state, and chemical composition. These results highlight the important role of iron redox chemistry in BrC formation under atmospherically relevant conditions.
|State||Published - Dec 2022|
Bibliographical noteFunding Information:
The authors acknowledge funding from the Natural Science and Engineering Council of Canada (NSERC) and to the U.S.A. National Science Foundation under award 1903744 to M.I.G. For technical assistance, the authors would like to thank Dr. Kitaev at Laurier for DLS, Drs. Smith and Goodfellow from the MS facility at the University of Waterloo for MALDI-TOF-MS, Dr. Castel from the Department of Chemical Engineering at the University of Waterloo for TGA, Dr. Andrei and Victoria Jarvis from the Canadian Centre for Electron Microscopy and MAX Diffraction Facility at McMaster University.
© 2022, The Author(s).
ASJC Scopus subject areas
- Chemistry (all)
- Environmental Chemistry
- Materials Chemistry