Indoor secondary organic aerosols: Towards an improved representation of their formation and composition in models

The formation of secondary organic aerosol (SOA) indoors is one of the many consequences of the rich and complex chemistry that occurs therein. Given particulate matter has well documented health effects, we need to understand the mechanism for SOA formation indoors and its resulting composition. Th...

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Bibliographic Details
Published in:Atmospheric Environment: X Vol. 240; p. 117784
Main Authors: Kruza, M., McFiggans, G., Waring, M.S., Wells, J.R., Carslaw, N.
Format: Journal Article
Language:English
Published: England Elsevier Ltd 01.11.2020
Subjects:
aerosols
alcohols
autoxidation
environment
Highly oxygenated organic molecules
Indoor air chemistry
model validation
nitrates
particulates
Secondary organic aerosol
vapor pressure
vapors
Vapour pressure
Volatile organic compound
Vapour pressure
Indoor air chemistry
Secondary organic aerosol
Volatile organic compound
Highly oxygenated organic molecules
ISSN:1352-2310, 2590-1621, 1873-2844, 2590-1621
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Summary:The formation of secondary organic aerosol (SOA) indoors is one of the many consequences of the rich and complex chemistry that occurs therein. Given particulate matter has well documented health effects, we need to understand the mechanism for SOA formation indoors and its resulting composition. This study evaluates some uncertainties that exist in quantifying gas-to-particle partitioning of SOA-forming compounds using an indoor detailed chemical model. In particular, we investigate the impacts of using different methods to estimate compound vapour pressures as well as simulating the formation of highly oxygenated organic molecules (HOM) via auto-oxidation on SOA formation indoors. Estimation of vapour pressures for 136 α-pinene oxidation species by six investigated methods led to standard deviations of 28–216%. Inclusion of HOM formation improved model performance across three of the six assessed vapour pressure estimation methods when comparing against experimental data, particularly when the NO2 concentration was relatively high. We also explored the predicted SOA composition using two product classification methods, the first assuming the molecule is dominated by one functionality according to its name, and the second accounting for the fractional weighting of each functional group within a molecule. The SOA composition was dominated by the HOM species when the NO2-to-α-terpineol ratio was high for both product classification methods, as these conditions promoted formation of the nitrate radical and hence formation of HOM monomers. As the NO2-to-α-terpineol ratio decreased, peroxides and acids dominated the simple classification, whereas for the fractional classification, carbonyl and alcohol groups became more important. •SOA concentration predictions are highly dependent on selected vapour pressure method used.•Highly oxygenated organic molecules form an important component of indoor SOA.•Composition of indoor SOA is highly complex and depends on indoor conditions.
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content type line 23
M. Kruza: Methodology, Software, Formal analysis, Investigation, Writing - original draft. G. McFiggans: Conceptualization, Methodology, Writing - original draft. M.S. Waring: Methodology. J.R. Wells: Methodology, Writing - original draft. N. Carslaw: Conceptualization, Methodology, Software, Investigation, Writing - original draft, Funding acquisition.
CRediT authorship contribution statement
ISSN:1352-2310
2590-1621
1873-2844
2590-1621
DOI:10.1016/j.atmosenv.2020.117784