Photodegradation of methyl thioglycolate particles as a proxy for organosulphur containing droplets

Abstract

Understanding the formation and transformation of sulphur-rich particles is of prime importance since they contribute to the global atmospheric sulphur budget. In this work, we performed a series of experiments on a photoactive organosulphur compound namely, methyl thioglycolate, as a model of an organosulphur species of marine origin. By investigating the photoproducts within levitated droplets, we showed that elemental sulphur (α-S8) and sulphate (SO42-) can be photochemically generated at the gas-liquid interface by heterogeneous interaction with gaseous O2 and H2O. These results demonstrate that the surface of levitated droplets facilitate the oxidation of methyl thioglycolate in the dark, while illumination is necessary to produce the oxidation in bulk experiments.

Photochemical Aging of Levitated Aqueous Brown Carbon Droplets

“…These results suggest that the red shift in absorbance observed in millimeter-sized BrC droplets could occur over a much faster time scale in smaller droplets. These studies ,, and the present results further emphasize the importance of single-droplet measurements and consideration of the role of the aerosol surface, to more accurately represent atmospheric aerosol chemistry in the laboratory.…”

“…Previous studies have used Raman microspectrometry to study the photochemistry of single acoustically levitated droplets of sodium nitrate and methyl thioglycolate. , A dark oxidation reaction was observed in acoustically levitated single methyl thioglycolate droplets that was not seen in the bulk phase, and the droplet surface was determined to play an important role in the dark oxidation reaction. Similarly, a difference between the droplet and bulk behavior was also observed in the present study, where Figure shows that the red shift in the absorbance maxima of illuminated aqueous BrC droplets is not observed in an illuminated cuvette.…”

Impact of the particle mixing state on the hygroscopicity of internally mixed sodium chloride–ammonium sulfate single droplets: a theoretical and experimental study

“…The deliquescence experiments, for all solutions containing a specific NaCl mole fraction, were conducted by generating a spray of fine droplets out of a medical nebulizer (Omrom MicroAIR U22, Japan) and trapping a droplet into the acoustic field as described in previous works. 39,40 In the present study, aqueous droplets ranging from 60 to 160 µm were trapped at room temperature (23°C) and at RH around 80%. After stabilization inside the acoustic field, droplets were dried by means of a N2 flow until reaching a RH of 10% where particles were completely solidified and free water Raman signals were absent from the spectra.…”