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Journal Article

Physical properties of secondary photochemical aerosol from OH oxidation of a cyclic siloxane


Janechek,  Nathan J.
External Organizations;

Marek,  Rachel F.
External Organizations;

Bryngelson,  Nathan
External Organizations;


Singh,  Ashish
IASS Institute for Advanced Sustainability Studies Potsdam;

Bullard,  Robert L.
External Organizations;

Brune,  William H.
External Organizations;

Stanier,  Charles O.
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Janechek, N. J., Marek, R. F., Bryngelson, N., Singh, A., Bullard, R. L., Brune, W. H., Stanier, C. O. (2019): Physical properties of secondary photochemical aerosol from OH oxidation of a cyclic siloxane. - Atmospheric Chemistry and Physics, 19, 3, 1649-1664.

Cite as: https://publications.iass-potsdam.de/pubman/item/item_4024902
Cyclic volatile methyl siloxanes (cVMS) are high-production chemicals present in many personal care products. They are volatile, hydrophobic, and relatively long-lived due to slow oxidation kinetics. Evidence from chamber and ambient studies indicates that oxidation products may be found in the condensed aerosol phase. In this work, we use an oxidation flow reactor to produce ∼100 µg m−3 of organosilicon aerosol from OH oxidation of decamethylcyclopentasiloxane (D5) with aerosol mass fractions (i.e., yields) of 0.2–0.5. The aerosols were assessed for concentration, size distribution, morphology, sensitivity to seed aerosol, hygroscopicity, volatility and chemical composition through a combination of aerosol size distribution measurement, tandem differential mobility analysis, and electron microscopy. Similar aerosols were produced when vapor from solid antiperspirant was used as the reaction precursor. Aerosol yield was sensitive to chamber OH and to seed aerosol, suggesting sensitivity of lower-volatility species and recovered yields to oxidation conditions and chamber operation. The D5 oxidation aerosol products were relatively non-hygroscopic, with an average hygroscopicity kappa of ∼0.01, and nearly non-volatile up to 190 ∘C temperature. Parameters for exploratory treatment as a semi-volatile organic aerosol in atmospheric models are provided.