RESEARCH AREAS
We focus on the physical and chemical phenomena that pertain to aerosols, which are suspended liquid droplets or solids that are a few tens of nanometers to several tens of micrometers in size. Aerosol particles serve as interesting reaction vessels in the atmosphere and their exposure is associated with adverse human health effects.
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Our research falls under three broad themes:
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Origin and Reactivity of Toxic Species in Aerosols
Inhalation of aerosols found in outdoor and indoor environments can lead to increases in the risk of mortality and morbidity and are two of the leading contributors to global disease burden (read more here). A prevailing toxicological mechanism by which aerosol exposure leads to these adverse health effects is oxidative stress, which results due to an imbalance of antioxidants defenses and oxidant production in the body.
For example, compounds found within aerosols can participate in redox cycling reactions which are proposed to play a major role in inducing oxidative stress, by catalytically consume antioxidants and/or generate reactive oxygen species (ROS). This ability is referred to as oxidative potential (OP).
A framework of redox cycling reactions involving a particle species (P), a reducing agent (RED) and ROS (superoxide, hydrogen peroxide, and hydroxyl radical).
Water-soluble organic components, quinones, and certain transition metals are some identified components in aerosols that can participate in these redox cycling reactions. Our research is focused on identifying outdoor and indoor sources of aerosols containing these species. Following the emission or formation of these aerosols into atmosphere, their physiochemical properties can be altered due to physical processes (i.e., evaporation via airmass dilution) and chemical processes (i.e., photolysis by UV light, reactions initiated by ozone and hydroxyl radicals, reactions with other aerosol components).
We are interested in evaluating whether these processes can form (and transform!) toxic aerosol components and impacts on aerosol oxidative potential.
Macromolecules in Atmospheric Aerosols
Organic compounds of molecular weights above several hundred Da (also referred to as humic-like-substances, HULIS) can affect the role of aerosols on climate as they readily absorb incoming solar radiation (therefore affecting the earth-atmosphere energy balance). Previous work in the group has observed that these compounds degrade slowly in the atmosphere, which indicates that these species may be long-lived in the atmosphere (and exert their environmental impacts for a longer period of time!).
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We are interested in characterizing the chemical composition of these macromolecules as well as exploring if they can exert toxic effects in the body by participating in redox cycling reactions (see above topic).
Changes in the absorption spectra of water-soluble organic compounds due to exposure to UVA light (published work).
Historial Air Quality Analysis and Ambient Aerosol Monitoring:
There remains a significant knowledge gap in the sources and toxicity of ambient PM in Atlantic Canada, a region that is underrepresented in previous ambient aerosol particle monitoring studies. In our group, we use two complementary strategies to better fill this gap:
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1) Using historial air quality monitoring datasets provided by National Air Pollution Surveillance (NAPS) Program, we evaluate the spatiotemporial trends of certain toxic species in ambient aerosol particles and examination of their inhalation exposure. Ongoing work focuses on identify the emission sources and chemical processes linked to water-soluble metals within aerosols.
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2) We will carry out ambient measurements of aerosol particle composition in Sackville, in order to identify the sources and spatiotemporal trends of toxic aerosol particles in this region.