Bringing Atmospheric Chemistry Home
Prof Allen H. Goldstein, University of California at Berkeley
The average American spends 90% of their time indoors, with 70% at home. We breathe an average of 17 kilograms of air per day, far more than the few kilograms per day of food and water that we ingest. From the perspective of human exposure and health, it is critical to understand indoor air quality. From the perspective of fundamental science, it is fascinating to explore the factors that govern the airborne chemical environment in which we spend most of our time living and breathing. From the perspective of Global Change, it is important to consider indoor air emissions as contributions to outdoor air pollution.
We seek to characterize and quantify volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) indoors in a way that enables fundamental understanding of the dynamic processes that influence their concentrations. Do these indoor chemicals originate from outdoor air, human activity, microbial activity, or from building materials? How do these chemical species change in a dynamic indoor environment, where temperature, humidity, and air exchange with outdoors can rapidly change? What chemical reactions occur in the indoor air and what are the dominant reactants (including oxidants like O3, OH, or NO3)? How do the organic compounds interact with surfaces, which can act as catalysts to accelerate certain chemical reactions or as a sink wherein chemicals accumulate?
In the seminar, results will be presented from several recent field campaigns in normally occupied residential homes. We applied proton-transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) to quantify concentrations of hundreds of different VOCs in real time at multiple locations indoors and outdoors. We also utilized our recently developed semivolatile thermal desorption aerosol gas chromatograph (SV-TAG) to acquire hourly SVOC measurements in both the gas and particle phases, including their partitioning, both indoors and outdoors. This investigation represents the first time that such monitoring has been undertaken in residences under normal occupancy. By collecting extensive metadata, including experimentally determining the air-exchange rates using tracer gases, we determined emission rates of hundreds of VOCs at hourly time resolution, traced the locations / activities associated with those emissions, and examined the role of environmental parameters on emissions. We characterize SVOC concentrations in the gas and particle phases, and the factors controlling their partitioning. We demonstrate that both VOC and SVOC concentrations in indoor air are markedly higher than those outdoors and that their dynamic behaviors indoors are strongly influenced by temperature with episodic enhancements related to cooking and cleaning. From ongoing analysis of these field campaign data, we aim to answer important questions about the indoor chemical and physical transformations of VOCs and SVOCs and their implications for human exposure.
Organised by :
Paul Palmer & Pawel Misztal