AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Effects of Environmental Factors on Chemically-Specific Indoor-Outdoor Ratios
ANITA JOHNSON, Michael Waring, Peter DeCarlo, Drexel University
Abstract Number: 349 Working Group: Indoor Aerosols
Abstract Aerosols transported to the indoor environment from outdoors undergo changes to physical and chemical properties, dependent on the original aerosol composition and conditions in each environment. Volatilization or condensation of aerosol components, including water, can have a significant impact on the concentration and composition of indoor aerosol of outdoor-origin. Differences in temperature and relative humidity (RH) are a result of occupant activity or operation of an HVAC system for comfort. This study measured real-time aerosol composition and size distribution of both indoor and outdoor air using an Aerodyne aerosol mass spectrometer (AMS), Magee Scientific aethalometer (AE-33), and a Brechtel scanning electrical mobility system (SEMS). Measurements were made in Philadelphia, PA in April 2013 and August 2014. Differing seasons for the studies allowed the investigation of aerosol composition with different gradients in temperature and RH. Distinct changes in indoor-outdoor (I/O) ratio were observed for the chemical species measured and factors determined by positive matrix factorization (PMF). PMF components included hydrocarbon-like organic aerosol (OA), oxygenated OA, and cooking OA. The water content of aerosols was estimated using Koehler Theory and the measured RH in each environment. The resulting differences in I/O ratio were then quantified as a function of temperature and RH gradients between indoors and outdoors. After accounting for mechanical losses using non-volatile aerosol sulfate, volatilization or condensation of aerosol of semi-volatile aerosol components were quantified as a function of the temperature gradient. During conditions when temperature was higher indoors and RH was higher outdoors, the losses of several aerosol species was observed. When the temperature indoors was lower and RH similar or lower, increases in several aerosol species (e.g. nitrate) was observed. These and other results will be presented.