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WALL-E/Vocus AIM data: Online particle phase chemical composition

Angelaki, Maria1; Donaldson, D. James2; Perrier, Sébastien1; Riva, Matthieu1, 3; George, Christian1

Published May 22, 2025 on Dryad. https://doi.org/10.5061/dryad.6q573n68z

Data files

May 22, 2025 version files 1.08 MB

Abstract

The spontaneous formation of OH radicals at the air-water interfaces of organic droplets was invstigated. In our study, we performed on line particle phase size resolved measurements, aiming to understand whether or not the oxidation process depends on the size of the particles. The on line measurements were performed using the WALL-E (wall free particle evaporator) particle phase inlet coupled with a Vocus AIM (adduct ionization mechanism) high resolution mass spectrometer. For the experiments of this study, iodide (I – ) was selected as the reagent ion, as it is suitable for the detection of carboxylic acids. We monitored the signal of the studied organic compounds (reactants) i.e., citric, maleic and aconitic acid as a function of particle size, as well as the signals of the generated products.As final oxidation products we identified a) Citric acid + OH: malonic, malic, hydroxy maleic and oxyglutaric acids, and C5H6O6, b) Maleic acid + OH: malic and acrylic acids and c) Aconitic acid + OH: malonic, malic, hydroxy maleic and oxyglutaric acids, and C4H4O6. The product yield was determined by dividing the product signal by the reactant signal. These results are only qualitative. Our size resolved online measurements revealed that the product yield formation is increasing as a function of the surface-to-volume ratio, meaning that the oxidation is promoted at smaller particles. This observation is in excellent agreement with the offline measurements described in the main text of the manuscript. 

The data given here contain all the raw signals of the above mentioned compounds as a function of sampling time (in minutes), i.e., time series. We also give the signals of water and iodine (reagent ion), with which we normalised the signals of the organics. Finally, we demonstrate some control experiments that we performed regarding the potential fragments of the parent compounds in the Wall-E source.