AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Impact of Air Exchange Rates on Aerosol Mass Fractions Describing Indoor-Generated Secondary Organic Aerosol
Somayeh Youssefi, MICHAEL WARING, Drexel University
Abstract Number: 242 Working Group: Indoor Aerosols
Abstract Secondary organic aerosol (SOA) formation due to the oxidation of reactive organic gases (ROG) is often parameterized with the aerosol mass fraction (AMF), which is the mass ratio of SOA produced to parent ROG reacted. The AMF is not constant and depends on the organic aerosol mass concentration. Most often, AMF curves are determined in batch systems. However, indoor settings undergo unintentional and intentional ventilation air exchange processes that lead to indoor air residence times of ~0.25 to 5 h and hence are better approximated as a continuous flow mixed reactor (CFMR) system. Little work has been done to evaluate ‘dynamic AMFs’ in CMFR systems over the range of typical indoor residence times for transient injections of reactant compounds. These dynamic AMFs may differ in magnitude from traditional ‘batch AMFs’ because of the shorter time for precursors to react, the flushing of gas- and SOA-phase products from the system with the exhaust air, and differences in deposition rates. In this work, dynamic AMFs for d-limonene ozonolysis were measured in a CFMR chamber system at three different air exchange rates and at different initial ozone:d-limonene ratios. Higher air exchange rates led to decreases in the observed AMFs and size-distributions with smaller median diameters and geometric standard deviations. Also, the AMF increased as the ozone:d-limonene ratio increased, potentially due to heterogeneous reactions. This study provides a framework to predict SOA formation indoors due to d-limonene ozonolysis over the range of typical air exchange rates and ozone:d-limonene ratios common to indoor environments.