In Situ Monitoring of the Aging of Mineral Particles by Methylglyoxal Using Infrared Spectroscopy. Part I: Unraveling Uptake under Dry Conditions

This study examines the aging process of atmospheric mineral particles through their interaction with methylglyoxal (MGL) under dry conditions, employing diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The mineral samples used are natural dusts from the Sahara (M’Bour) and Gobi deserts, along with their principal constituents, quartz (SiO2) and calcite (CaCO3). DRIFTS spectra indicate that MGL uptake on SiO2, CaCO3, M’Bour, and Gobi dust surfaces is influenced by both reactive and nonreactive pathways. Reactive uptake results in the formation of carboxylic acids, enols, or oligomers, contributing to secondary organic aerosol formation. MGL is preferentially taken up by OH sites. Although uptake on CaCO3 and Gobi dust is irreversible, M’Bour dust exhibits partial reversibility (∼25%). These findings highlight the significant role of mineral dust in atmospheric chemical processes, necessitating further investigations to evaluate the influence of humidity on uptake mechanisms and secondary organic aerosol formation.