Abstract:
Because people spend the majority of their time indoors, exposure to ambient (outdoor-generated) PM2.5 mostly occurs in the indoor environment. Organics are a major component of ambient PM2.5; however, predicting indoor exposures to ambient organic aerosol (OA) is complicated by shifts in the gas-particle partitioning of ambient organics with outdoor-to-indoor transport due to changes in temperature, surface area, and the availability of organic particulate matter for sorption. The change in the gas-particle partitioning of ambient organics with outdoor-to-indoor transport was calculated for 167 homes sampled during the Relationships, of Indoor, Outdoor, and Personal Air Study using measured temperatures, measured particulate organic matter concentrations, and published OA volatility basis sets (VBS). To evaluate the sensitivity of these calculations to uncertainties in the thermodynamic properties of ambient OA, partitioning shifts were calculated assuming enthalpies of vaporization (ΔHvap) of 100 and 50 kJ/mol. Partitioning shifts were highly sensitive to ΔHvap assumptions and resulted in changes in indoor concentrations of ambient OA of 13 - 27%, on average, depending on the assumed ΔHvap. The lack of a clear understanding of the thermodynamic properties of ambient OA contributes to uncertainty in the magnitude and direction of partitioning shifts with outdoor-to-indoor transport and, thus, contributes to uncertainty in ambient OA exposures and the associated health effects. In the proposed research, aerosol composition and meteorological data measured in the Po Valley, Italy during the Pan-European Gas- Aerosols-climate interaction Study (PEGASOS) will be used to explore atmospheric processes and aerosol formation mechanisms that influence the volatility of organic aerosols. By elucidating the thermodynamic properties of organic aerosol, this research will contribute to a more thorough understanding of the behavior of organic aerosol in the indoor environment, while also contributing to the broader scientific effort to improve the representation of secondary organic aerosol formation and behavior in climate and air quality models.
Because people spend the majority of their time indoors, exposure to ambient (outdoor-generated) PM2.5 mostly occurs in the indoor environment. Organics are a major component of ambient PM2.5; however, predicting indoor exposures to ambient organic aerosol (OA) is complicated by shifts in the gas-particle partitioning of ambient organics with outdoor-to-indoor transport due to changes in temperature, surface area, and the availability of organic particulate matter for sorption. The change in the gas-particle partitioning of ambient organics with outdoor-to-indoor transport was calculated for 167 homes sampled during the Relationships, of Indoor, Outdoor, and Personal Air Study using measured temperatures, measured particulate organic matter concentrations, and published OA volatility basis sets (VBS). To evaluate the sensitivity of these calculations to uncertainties in the thermodynamic properties of ambient OA, partitioning shifts were calculated assuming enthalpies of vaporization (ΔHvap) of 100 and 50 kJ/mol. Partitioning shifts were highly sensitive to ΔHvap assumptions and resulted in changes in indoor concentrations of ambient OA of 13 - 27%, on average, depending on the assumed ΔHvap. The lack of a clear understanding of the thermodynamic properties of ambient OA contributes to uncertainty in the magnitude and direction of partitioning shifts with outdoor-to-indoor transport and, thus, contributes to uncertainty in ambient OA exposures and the associated health effects. In the proposed research, aerosol composition and meteorological data measured in the Po Valley, Italy during the Pan-European Gas- Aerosols-climate interaction Study (PEGASOS) will be used to explore atmospheric processes and aerosol formation mechanisms that influence the volatility of organic aerosols. By elucidating the thermodynamic properties of organic aerosol, this research will contribute to a more thorough understanding of the behavior of organic aerosol in the indoor environment, while also contributing to the broader scientific effort to improve the representation of secondary organic aerosol formation and behavior in climate and air quality models.