Water-Soluble Species in Residential Air, Air-Surface Dynamics and the Influence of Surface Films and Water

Buildings are humid and limitedly vented spaces with large surface area-to-volume ratios. As a result, air-surface dynamics of water-soluble gases play a substantial role in indoor chemistry. Water-soluble gases can be an average of 15x times more concentrated indoors than outdoors and are associated with adverse health effects and poor indoor air quality. Building materials and their associated surface films (i.e., nanoscale grime of surface-bound chemicals) provide reservoirs for water-soluble gases to partition and undergo heterogeneous reactions, altering human exposure and building chemistry. Multiphase chemistry of water-soluble gases with atmospheric waters (i.e., fog, clouds, rainwater, and aqueous aerosols) is recognized to be key processes in atmospheric chemistry that impacts outdoor air quality and human health. Despite most inhalation exposures occurring indoors and the high potential for aqueous-mediated surface chemistry in buildings, multiphase interactions of water-soluble pollutants in the indoor environment are understudied compared to the outdoor environment.This dissertation research combines field measurements, predictive modeling, and laboratory experiments to improve our understanding of indoor air-surface interactions of common water-soluble pollutants and assess the influence of humidity. Time-resolved field measurements demonstrated that airborne total water-soluble organic carbon (WSOC) existed primarily in the gas-phase and that its gas-phase concentration dynamics were highly regulated by near-surface reservoirs. Real-time indoor NH3 concentration dynamics were simulated in a multi-compartment box model that enabled prediction of surface reservoir volumes in ventilation ductwork and building materials, which increased in size at higher relative humidity. Laboratory experiments determined that humidity substantially increased surface removal of organic hydroperoxides (ROOHs) to authentically soiled window glass (only when soiled) and provided the first measurements of the deposition velocity and reaction probability of ROOHs with indoor surfaces. This dissertation provides new insights into the role of water and surface reservoirs on the behavior of 3 important water-soluble pollutants. It is critical for laboratory experiments attempting to mimic the complex surface chemistry of the indoor environment to include realistic conditions (soiled surfaces + humidity) and for indoor chemical transport model frameworks to incorporate surface reservoirs of RH-dependent volumes for accurate predictions.