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RESEARCH AREAS

We focus on the physical and chemical phenomena that pertain to aerosols, which are suspended liquid droplets or solids, as they serve as interesting reaction vessels in the atmosphere and their exposure is associated with adverse human health effects. 

Our research falls under three broad themes: 

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).   

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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 in atmosphere, their physiochemical properties can be altered due to physical (i.e., evaporation via airmass dilution) and chemical (i.e., photolysis by UV light, reactions initiated by ozone and hydroxyl radicals) processes. We are interested in evaluating whether these processes can form (and transform!) the identified 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!).

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).

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Changes in the absorption spectra of water-soluble organic compounds due to exposure to UVA light (published work).

New Analytical Tools for Aerosol Measurements 

Chemical and physical properties of aerosols are highly diverse; sizes range from a few nanometers to tens of micrometers, comprised of organic, inorganic, and metallic species of a wide range of concentrations from nanograms to micrograms per cubic meter of air (!). These aerosol properties are also highly variable spatially and temporally, and so quantitative analysis of aerosols is a highly challenging (and fun!) issue for analytical chemists to tackle. 

In our group, we are interested in developing new tools to measure metal species in aerosols and to characterize chemical properties that are relevant to aerosol toxicity, in particular, the application of  electrochemical techniques for these types of analysis. 

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