10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Evaluation of the Molecular Composition of Particle- and Gas-Phase Material in an Indoor Residential Environment using Positive Matrix Factorization
CLAIRE FORTENBERRY, Michael Walker, Audrey Dang, Arun Loka, Gauri Date, Karolina Cysneiros de Carvalho, Glenn Morrison, Brent Williams, Washington University in St. Louis
Abstract Number: 1570 Working Group: Indoor Aerosols
Abstract Natural ventilation (e.g., window opening and closing to regulate indoor temperature) promotes infiltration of outdoor pollutants and oxidants into the indoor environment, and infiltrating oxidants like ozone (O3) can drive formation of new pollutants through oxidative chemistry [1]. Changes in air exchange rates with window opening can also drive volatilization and resuspension of deposited material. Many common indoor air pollutants are semi- or intermediately volatile and therefore actively partition between the gas and particle phases. Because respiratory deposition depends on chemical and physical properties like diffusivity and particle mobility diameter [2,3], greater understanding of pollutant phase partitioning is needed to improve exposure estimates and inform residential building standards.
The Air Composition and Reactivity from Outdoor aNd Indoor Mixing (ACRONIM) field campaign was conducted in the summer of 2016 at a single-family residence in St. Louis, Missouri. A Thermal desorption Aerosol Gas chromatograph (TAG), which pairs automated aerosol collection with thermal desorption and online analysis by gas chromatography-mass spectrometry (GC-MS) [4], was used for chemical measurements of indoor particles and gases. Samples were collected alternately indoors and outdoors with two-hour time resolution throughout the study under three major natural ventilation conditions (all windows closed, one window open, two windows open). A denuder difference method, wherein the TAG sampled alternately through a diffusion denuder and a bypass line, was used to determine the relative contributions of gases and particles to compound abundances.
Using mass spectral databases, we identified approximately 200 compounds in indoor and outdoor ambient TAG samples. A subset of these compounds spanning a range of volatilities and chemical functionalities were integrated, and positive matrix factorization (PMF) analysis was used to identify co-varying compounds across the measurement period. A three-factor PMF solution resolved one indoor factor, one outdoor factor, and one factor corresponding to indoor compounds enhanced with window opening. Compounds loading into the enhanced factor include indoor-originating phthalates and esters common in personal care products, indicating increased volatilization of deposited material with changes in air exchange rate. Loading of acids and aldehydes into the enhanced factor indicate formation of compounds through oxidative chemistry. Higher-factor PMF solutions provide improved resolution of outdoor-originating compounds, including polycyclic aromatic hydrocarbons (PAHs) associated with combustion. Finally, by assessing differences between denuded and undenuded compound abundances, we found that many compounds measured by the TAG in the indoor environment exist significantly in the gas phase, with less than 40% of the inte-grated compounds exhibiting a particle-phase fraction greater than 0.5.
[1] Morrison, G. C., Current Sustainable Renewable Energy Reports, 2(2), 33-40, 2015. [2] Patton, J. S., Byron, P. R., Nature Reviews Drug Discovery, 6(1), 67-74, 2007. [3] Watson, A. Y., Bates, R. R., Kennedy, D., editors: Air Pollution, the Automobile, and Public Health. Washington (DC): National Academies Press (US), 1988. [4] Williams, B. J., Goldstein, A. H., Kreisberg, N. M., Hering, S. V. Aerosol Science and Technology, 40(8), 627-638, 2006.