Reactive nitrogen species—nitrous acid (HONO), ammonia (NH3), and amines (NR3)—are present indoors. These reactive nitrogen species are important because of the associated chemical and physical transformations. Outdoors, amines are implicated in particle formation. And HONO is photolabile, which means it decomposes in the presence of light, generating the important oxidant hydroxyl radical. Hydroxyl radicals can then rapidly react with volatile organic compounds, leading to secondary aerosol formation. Detecting concentrations of these chemicals is vital to answering key questions about the chemistry of indoor environments, such as “What is the role of ammonia and amines in indoor chemistry?” and “To what extent do they contribute to new particle formation?” This grant funds a team led by Trevor VandenBoer, Visiting Professor of Chemistry at York University, that aims to develop analytical platforms for the detection of reactive nitrogen indoors. The work plan has three parts. First, the team plans to develop new selective sampling methodologies for the passive collection of HONO, ammonia, and amines in indoor environments. Second, they plan to design and construct a real-time monitor for HONO and total reactive nitrogen that can discriminate between gas and particulate pools. Finally, they will validate the new methods both against traditional benchmarks and through deployment in various indoor environments. The team plans to share their findings through peer-reviewed articles and presentations at several scientific and professional conferences. One postdoctoral fellow, three graduate students, and numerous undergraduates will be trained in the course of the project.

Funds from this grant support a team led by Brent Williams of Washington University in St. Louis to improve our ability to collect and analyze indoor air samples through the development of a chemically resolved volatility and polarity separator. The project aims to build and test a new field-deployable automated instrument for the simultaneous measurement of organic gas and particle chemical composition. The work plan has three parts. First, Williams and his team will develop a modified volatility and polarity separator capable of detailed chemical characterization of the particle phase and gas phase of airborne indoor organic material. Next they will demonstrate the strengths of the new measurement capacity through controlled laboratory studies and through an indoor field study. Last, they will develop an open-access volatility- and polarity-separated chemical profile database of indoor sources and transformations, along with open-access data analysis codes for use by the indoor air research community. Predicted outcomes of this project include the new instrument, the open access data base, and new knowledge about the composition of indoor air. The team plans to share their findings through multiple peer-reviewed publications and conference presentations on instrument development and through open-access chemical databases and analysis codes. One postdoctoral fellow and three graduate students will be trained.

Mass spectrometry is a technique that ionizes chemical species and then sorts them by mass. While useful, spectrometry does not distinguish between chemical isomers, species with the same number and types of atoms as another chemical species. This is important; isomers possess distinct properties because their atoms are arranged into different chemical structures. Isomers may differ, for instance, in reactivity, vapor pressure, and the identity of products. This grant will support work by Delphine Farmer, Associate Professor of Chemistry at Colorado State University, in collaboration with Ellison Carter, Assistant Professor of Civil and Environmental Engineering, to develop and test novel software for time-of-flight chemical ionization mass spectrometry that will allow researchers to identify isomers based on differences in binding energy. Funded work includes software development, calibration, and validation using both individual isomers and mixtures of isomers, and field testing in an unoccupied residence. The project will result in new software for both data acquisition and analysis, as well as field datasets, for sharing with the broader scientific community. The findings will be shared through publications from the instrument development component of the proposal, and additional publications when the instrument is used in an indoor study. The project will train at least one Ph.D. student in indoor chemistry and mass spectrometry instrument development.

Funds from this grant support a team lead by Virginia Tech’s Gabriel Isaacman-VanWertz to improve our ability to detect chemical isomers indoors through the development of a field-deployable gas chromatograph coupled to a chemical ionization mass spectrometer. This proposed research is divided into three technical tasks: First, Issacman-VanWertz will engineer the physical and technical interface between the major instrument components. Then he will characterize and calibrate the new instrument. Finally, he will deploy the instrument in an on-campus controlled indoor environment to examine emissions. The team plans to share their findings through peer-reviewed articles and presentations at several scientific and professional conferences.

Test bed studies require Chemistry of Indoor Environment researchers to be able to make important indoor chemistry measurements quickly and at low cost. Unfortunately, there are no good low-cost sensors for volatile organic compounds (VOCs). This grant funds an effort to build one. It’s an important effort. Many VOCs are harmful to human health and even those that aren’t can react with oxidants, eventually leading to new particle and aerosol formation. Over the next three years, Jesse Kroll—Associate Professor of Civil and Environmental Engineering and Associate Professor of Chemical Engineering at the Massachusetts Institute of Technology—will attempt to develop a low-cost monitor for measurements of volatile organic compounds in the indoor environment. The work plan has two major parts: the construction, characterization, and optimization of the VOC monitor, and the use of several such monitors in real indoor environments, providing both a proof-of-concept and initial measurements of indoor VOC levels. The primary output of this project will be the monitor and associated algorithms as well as the associated research results. Descriptions of the optimized monitor design and calibration algorithms will be disseminated broadly via the peer-reviewed, open-access literature and conference presentations. At least one graduate student will be trained.  

Outdoors, strong ultraviolet light from the sun drives the photolysis of ozone, resulting in the production of hydroxyl (OH) radicals. Hydroxyl radicals, sometime referred to as “nature’s vacuum cleaner” are highly reactive and short lived. They can react with volatile organic compounds leading to the formation of peroxy radicals. These radicals, in turn, react rapidly with a range of compounds, eventually producing secondary organic aerosols in the atmosphere. Yet much is unknown. Despite the absence of the strong ultraviolet light that drives oxidation reactions outdoors, there is preliminary evidence that indoor environments contain hydroxyl radicals. The pathways that generate these radicals and the role they play in indoor chemistry are mysteries. Funds from this grant support an effort by Philip S. Stevens (Indiana University), in collaboration with Brandon Boor (Purdue University), to examine radical concentrations and associated aerosol production in indoor environments. The team aims to improve our understanding of oxidation chemistry in indoor environments through comprehensive measurements of radical concentrations, including their sources and sinks, as well as the impact of radical concentrations on aerosol production in several laboratories, chambers, and at least one residence. The results of the studies will be shared through peer-reviewed journals and through presentations at meetings of the International Society of Indoor Air Quality and Climate, the American Chemical Society, and the American Association for Aerosol Research. At least four students will be trained.

Hydrolysis is a reaction in which water is used to break down chemical bonds. Preliminary evidence suggests hydrolysis reactions could be very important indoors, breaking down common man-made ester (MME) compounds like those found in PVC pipes, and diffusing the resulting degradation products into the air. This grant funds a project by V. Faye McNeill, Associate Professor of Chemical Engineering at Columbia University, to assess the impact of hydrolysis reactions of a range of man-made esters—occurring on damp indoor surfaces—on indoor air quality. Grant funds will allow McNeill to adapt her outdoor atmospheric chemistry model, GAMMA (Gas-Aerosol Model for Mechanism Analysis), for application to the indoor environment. The adapted model, GAMMA-CIE, will introduce MME species, intermediates, and reaction products into the aqueous phase chemical mechanism, incorporate mass transfer between the aqueous and gas phases, and model oxidation in the gas phase. In addition to this modeling work, McNeill will perform laboratory measurements to provide missing data for the MME hydrolysis cascade under alkaline conditions and will examine the effect of acidic pH and ionic content of the aqueous film on MME hydrolysis kinetics. Among the MME compounds to be characterized are Texanol, a component of latex paints; TXIB (trimethyl pentanyl diisobutyrate); BBzP (benzyl butyl phthalate); and DEHA (diethylhydroxylamine). Last, McNeil will use the modified model to predict indoor air quality under typical domestic and commercial building scenarios. The model will simulate the fate of esters and the role of damp surfaces in realistic indoor conditions, providing new insights about indoor chemistry.