10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Seasonal Variation in the Composition of Submicron Indoor Aerosols of Outdoor Origin
Anita Avery, Michael Waring, PETER DECARLO, Drexel University
Abstract Number: 1447 Working Group: Indoor Aerosols
Abstract Outdoor-originated aerosols play a key role in indoor air quality, especially in indoor spaces without strong sources. Since outdoor aerosol varies both spatially and temporally over short (diurnal) and long (seasonal) time scales. We examined the effect of these changes in aerosol loading and chemical composition on indoor aerosol, by examining both indoor and outdoor aerosols in real time in an urban classroom in winter and summer seasons, using an aerosol mass spectrometer (AMS) and a suite of gas phase instruments. Factor analysis of the organic aerosol components identified 3 factors in common between seasons, including hydrocarbon-like, cooking, and oxidized organic aerosol (HOA, COA, and OOA). We report a sulfate-normalized indoor-outdoor ratio (I/O)i/SO4 to account for seasonal differences and variation in ventilation (HVAC operation) to elucidate emissions and chemically-based loss processes between environments. Outdoor aerosols transported indoors in wintertime experience an increased environmental temperature which can drive off water and volatile components, while in summertime aerosols experience a decrease in temperature upon transport indoors and the reverse can happen. However, the degree to which any effect is observed is dependent on the starting (outdoor) aerosol population and the magnitude of change (in temperature, RH, etc.). The median (I/O)i/SO4 values for nitrate, black carbon (BC), total organics, and HOA were smaller in wintertime when temperature gradients between environments favored losses of volatile components; (I/O)i/SO4 values greater than one indicated indoor sources (or less loss) of HOA, BC, and COA. Calculated aerosol liquid water (ALW), as a function of the environmental conditions (temperature and humidity) and the relative contribution of hygroscopic components, varied significantly by season with higher levels in the summertime providing the possibility of aqueous or otherwise liquid processing. This work describes the linkages between chemically-specific variations in exposure between seasons.