AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Shifts in the Gas-Particle Partitioning of Ambient Organics with Transport into the Indoor Environment
NATASHA HODAS, Barbara Turpin, Rutgers University
Abstract Number: 62 Working Group: Aerosol Exposure
Abstract PM$_(2.5) concentrations measured at central-site monitors are commonly used to estimate exposure to ambient PM$_(2.5) in epidemiologic analyses; however, people spend the majority of time indoors. Estimating indoor exposures to ambient organic aerosols (OA) is complicated by the fact that shifts in the gas-particle partitioning of ambient organics can occur with indoor transport due to indoor-outdoor differences in temperature and in the availability of organic particulate matter for sorption. The change in the gas-particle partitioning of ambient organics with indoor transport was calculated for 170 homes sampled during the Relationships, of Indoor, Outdoor, and Personal Air Study using measured indoor and outdoor temperatures, measured particulate organic carbon concentrations, and published ambient OA volatility basis sets. To evaluate the sensitivity of these calculations to uncertainty in the physiochemical properties of ambient OA, partitioning shifts were calculated assuming enthalpies of vaporization of 100 and 50 kJ/mol. Multiple linear regression (MLR) was used to determine the extent to which shifts in partitioning could be attributed to indoor-outdoor temperature differences and to differences in the availability of organic matter for sorption. Partitioning shifts were highly sensitive to enthalpy-of-vaporization assumptions. On average, the change in the fraction of organic matter in the particle phase was 39% and 17% for enthalpies of vaporization of 100 and 50 kJ/mol, respectively. The MLR models explained the majority of the variability in shifts in partitioning (R$^2 = 0.64 - 0.90); however, whether partitioning shifts were driven by changes in temperature or OA concentrations varied with home location, season, and enthalpy-of-vaporization assumption. The MLR models developed in this work have the potential to provide simple parameterizations of shifts in the gas-particle partitioning of ambient organics with indoor transport. However, further work is needed to address uncertainty regarding the physiochemical properties and volatilities of ambient OA.