Preprints
https://doi.org/10.5194/acp-2021-353
https://doi.org/10.5194/acp-2021-353

  03 May 2021

03 May 2021

Review status: this preprint is currently under review for the journal ACP.

Secondary Organic Aerosol Formation from the Oxidation of Decamethylcyclopentasiloxane at Atmospherically Relevant OH Concentrations

Sophia M. Charan1, Yuanlong Huang1, Reina S. Buenconsejo1, Qi Li2, David R. Cocker III2, and John H. Seinfeld1 Sophia M. Charan et al.
  • 1California Institute of Technology, Pasadena, California 91125, United States
  • 2University of California – Riverside, Riverside, California 92521, United States

Abstract. Decamethylcyclopentasiloxane (D5, C10H30O5Si5) is measured at ppt levels outdoors and ppb levels indoors. Primarily used in personal care products, its outdoor concentration is correlated to population density. Since understanding the aerosol formation potential of volatile chemical products is critical to understanding particulate matter in urban areas, the secondary organic aerosol yield of D5 was studied under a range of OH concentrations, OH exposures, NOx concentrations, and temperatures. The secondary organic aerosol (SOA) yield from the oxidation of D5 is extremely dependent on the OH concentration, and differing measurements of the SOA yield from the literature are resolved in this study. Here, we compare experimental results from environmental chambers and flow tube reactors. Generally, there are high SOA yields (> 68 %) at OH mixing ratios of 5 × 109 molec cm−3. At atmospherically relevant OH concentrations, the SOA yield is largely < 5 % and usually ~1 %. This is significantly lower than SOA yields used in emission and particulate matter inventories and demonstrates the necessity of OH concentrations similar to the ambient environment when extrapolating SOA yield data to the outdoor atmosphere.

Sophia M. Charan et al.

Status: open (until 28 Jun 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Sophia M. Charan et al.

Sophia M. Charan et al.

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Short summary
In this study, we investigate the secondary organic aerosol formation potential of decamethylcyclopentasiloxane (D5), which is used as a tracer for volatile chemical products and measured in high concentrations both outdoors and indoors. By performing experiments in different types of reactors, we find that that D5’s aerosol formation is highly dependent on the OH concentration and, at atmospherically relevant OH levels, D5 forms little aerosol. We also reconcile results from other studies.
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