Issue 9, 2023

Effective mass accommodation for partitioning of organic compounds into surface films with different viscosities

Abstract

Indoor surfaces can act as reservoirs and reaction media influencing the concentrations and type of species that people are exposed to indoors. Mass accommodation and partitioning are impacted by the phase state and viscosity of indoor surface films. We developed the kinetic multi-layer model KM-FILM to simulate organic film formation and growth, but it is computationally expensive to couple such comprehensive models with indoor air box models. Recently, a novel effective mass accommodation coefficient (αeff) was introduced for efficient and effective treatments of gas–particle partitioning. In this study, we extended this approach to a film geometry with αeff as a function of penetration depth into the film, partitioning coefficient, bulk diffusivity, and condensed-phase reaction rate constant. Comparisons between KM-FILM and the αeff method show excellent agreement under most conditions, but with deviations before the establishment of quasi-equilibrium within the penetration depth. We found that the deposition velocity of species and overall film growth are impacted by bulk diffusivity in highly viscous films (Db ∼<10−15 cm2 s−1). Reactions that lead to non-volatile products can increase film thicknesses significantly, with the extent of film growth being dependent on the gas-phase concentration, rate coefficient, partitioning coefficient and diffusivity. Amorphous semisolid films with Db > ∼10−17–10−19 cm2 s−1 can be efficient SVOC reservoirs for compounds with higher partitioning coefficients as they can be released back to the gas phase over extended periods of time, while glassy solid films would not be able to act as reservoirs as gas-film partitioning is impeded.

Graphical abstract: Effective mass accommodation for partitioning of organic compounds into surface films with different viscosities

Supplementary files

Article information

Article type
Paper
Submitted
18 May 2023
Accepted
04 Aug 2023
First published
04 Aug 2023

Environ. Sci.: Processes Impacts, 2023,25, 1464-1478

Effective mass accommodation for partitioning of organic compounds into surface films with different viscosities

P. S. J. Lakey, B. E. Cummings, M. S. Waring, G. C. Morrison and M. Shiraiwa, Environ. Sci.: Processes Impacts, 2023, 25, 1464 DOI: 10.1039/D3EM00213F

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