The NBD research group at the University of British Columbia (UBC) is interested in studying the chemical mechanisms in which organic compounds, often pollutants, are oxidized and degraded in the atmosphere. Whether they are emitted volatile organic compounds (VOCs) from personal care products (fragrances), from smoking, from household activities such as cleaning and cooking, we want to fundamentally understand what happens to these molecules in the air. Four types of questions guide our research program:

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(1) How fast do these molecules get oxidized? To answer this question, we conduct kinetic experiments in an analytical atmospheric gas phase chamber using online mass spectrometry tools.

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(2) What products do they generate and are these products of concern for human health? To answer this question, we perform product elucidation experiments with online and offline mass spectrometry.

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(3) What is the mechanism of the transformation of these molecules in our atmosphere? To answer this question, we carry out control experiments with different oxidants and different proposed intermediates to support a proposed chemical mechanism. We are also interested in supporting our proposed mechanisms through computational chemistry studies using Gaussian.

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(4) How are these molecules transformed in the atmosphere, by which oxidant and why? To answer this multistep question, we undertake oxidant-specific quantification experiments to look for hydrogen peroxide, singlet oxygen, OH radicals, nitrate radicals and ozone and how they contribute to the oxidation of our molecules of interest. We also strive to understand how these different oxidants are generated in the gas phase and in the particle phase of an aerosol and which factors govern their steady-state concentrations.

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We aim to provide a comprehensive assessment of the chemical reactions governing atmospheric processing, a goal only possible with state-of-the-art and sophisticated analytical chemistry tools and instruments. One instrument that effectively tackles all four of the key questions above is an online proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS from Tofwerk/Aerodyne Research Inc). The experiments described are conducted in a home-built Teflon bag smog chamber and in glass flow tubes. The PTR-ToF-MS then measures the molecules of interest and follow their fate as a function of exposure to atmospheric processing (like photolysis, oxidation, humidity, etc.).

 

Project leader at UBC: PhD student Ayomide Akande