Emerging investigator series: chemical and physical properties of organic mixtures on indoor surfaces during HOMEChem

Rachel E. O'Brien; Ying Li; Kristian J. Kiland; Erin F. Katz; Victor W. Or; Emily Legaard; Emma Q. Walhout; Corey Thrasher; Vicki H. Grassian; Peter F. DeCarlo; Allan K. Bertram; Manabu Shiraiwa

doi:10.1039/D1EM00060H

Emerging investigator series: chemical and physical properties of organic mixtures on indoor surfaces during HOMEChem†

Rachel E. O'Brien,

*^a Ying Li,

^b Kristian J. Kiland,

^c Erin F. Katz,‡^d Victor W. Or,

^e Emily Legaard,^a Emma Q. Walhout,^a Corey Thrasher,^a Vicki H. Grassian,

^ef Peter F. DeCarlo,

^g Allan K. Bertram^c and Manabu Shiraiwa

^b

Author affiliations

* Corresponding authors

^a Department of Chemistry, William & Mary, Williamsburg, VA, USA
E-mail: reobrien@wm.edu

^b Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA

^c Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada

^d Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA

^e Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, USA

^f Scripps Institution of Oceanography and Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, USA

^g Department of Environmental Health and Engineering, Johns Hopkins University, Baltimore, MD, USA

Abstract

Organic films on indoor surfaces serve as a medium for reactions and for partitioning of semi-volatile organic compounds and thus play an important role in indoor chemistry. However, the chemical and physical properties of these films are poorly characterized. Here, we investigate the chemical composition of an organic film collected during the HOMEChem campaign, over three cumulative weeks in the kitchen, using both Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) and offline Aerosol Mass Spectrometry (AMS). We also characterize the viscosity of this film using a model based on molecular formulas as well as poke-flow measurements. We find that the film contains organic material similar to cooking organic aerosol (COA) measured during the campaign using on-line AMS. However, the average molecular formula observed using FT-ICR MS is ∼C₅₀H₉₀O₁₁, which is larger and more oxidized than fresh COA. Solvent extracted film material is a low viscous semisolid, with a measured viscosity <10⁴ Pa s. This is much lower than the viscosity model predicts, which is parametrized with atmospherically relevant organic molecules, but sensitivity tests demonstrate that including unsaturation can explain the differences. The presence of unsaturation is supported by reactions of film material with ozone. In contrast to the solvent extract, manually removed material appears to be highly viscous, highlighting the need for continued work understanding both viscosity measurements as well as parameterizations for modeled viscosity of indoor organic films.

This article is part of the themed collections: Recent Open Access Articles and Emerging Investigator Series

Environmental Science: Processes & Impacts

Emerging investigator series: chemical and physical properties of organic mixtures on indoor surfaces during HOMEChem†

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Emerging investigator series: chemical and physical properties of organic mixtures on indoor surfaces during HOMEChem

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