Master, PhD and postdoc projects available Interested in joining the Nadine Borduas-Dedekind group at Department of Chemistry, University of British Columbia?

Master, PhD and postdoc projects available

Interested in joining the Nadine Borduas-Dedekind group at Department of Chemistry, University of British Columbia?

Research and Teaching Interests

Atmospheric Chemistry

The atmosphere is like a large round bottom flask, where countless chemical reactions are taking place. For example, the emissions from anthropogenic and biogenic sources are the starting materials. The wind and turbulence act as stir bars and the sunlight acts as a hot plate. The round bottom flask also contains water, a crucial molecule to atmospheric chemistry, because it transports heat through the atmosphere, serves as a solvent for atmospheric aqueous reactions, and cleans the atmosphere through wet deposition. Water is also a precursor to the major oxidant in the atmosphere: the hydroxyl (OH) radical, the so-called atmospheric detergent. The real atmosphere has all these processes occurring simultaneously and we arguably understand a fraction of the chemical processes that lead to air pollution and climate change!

The NBD research group has an atmospheric organic chemistry expertise applied to the fields of indoor and outdoor air chemistry, and to biogeochemistry and atmospheric ice nucleation (Figure 1). Our research is collaborative to allow us to ask big-picture questions with implications for air quality and climate.

Figure 1: This hierarchy of research interests in the NBD Group includes applying atmospheric organic chemistry expertise to big picture problems such as air quality and climate change. The specific research projects fall within the context of indoor air, outdoor air, biogeochemistry and atmospheric ice nucleation.

Gas-Phase Chemical Kinetics and Mechanisms

The NBD Group 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 boreal forests, (sesquiterpenes) or from the marine biota (organo-sulfur and -selenium), we want to fundamentally understand what happens to these molecules in the air. Four types of questions guide our research.

(1) How fast do these molecules get oxidized?

(2) What products do they generate and are these products of concern for human health?

(3) What are the mechanisms of oxidation of these molecules in our atmosphere?

(4) How are these molecules transformed in the atmosphere, by which oxidant and why?

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 Ionicon). Many of these experiments described will be conducted in a home-built Teflon bag smog chamber and in glass flow tubes. The PTR-ToF-MS will then measure the molecules of interest and follow their fate as a function of exposure to atmospheric processing (like photochemistry, oxidation, humidity, etc.).

Atmospheric Ice Nucleation

Cloud glaciation is an atmospheric process with important implications for climate and weather. Indeed, clouds made of liquid water and of ice crystals impact the global radiative balance of the atmosphere by reflecting incoming solar radiation and by absorbing outgoing terrestrial radiation. Ice nucleation is the process of liquid water or water vapor freezing. It occurs when supercooled water droplets freeze into ice crystals; a process which occurs spontaneously at or below – 38 °C and which is termed homogeneous freezing. Yet, ice exists at warmer temperatures due to heterogeneous freezing. Heterogeneous freezing requires an ice nucleating particle (INP) for water to condense on and form an ice crystal. The most relevant freezing pathway observed and modelled in mixed-phase clouds is immersion freezing which involves an INP submerged within a supercooled droplet. This freezing mechanism has been quantified to account for up to 70% of freezing in mixed phase clouds and is thus the focus of our droplet Freezing Ice Nuclei Counter (FINC) home-built instrument.

The NBD Group studies the ability of macromolecules, from organic aerosols and present in supercooled droplets, to nucleate ice in the atmosphere. We have two main research questions:

(1) How does organic matter affect the supercooled liquid to ice ratio in mixed-phase clouds?

(2) Can the chemical properties of organic aerosols be used to predict cloud glaciation temperatures to improve parameterization of cloud microphysics in models?

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