PhD Research

Inverse Modeling of NOx and NH3 Precursor Emissions Using the Adjoint of CMAQ

Air quality models are utilized by the U.S. EPA to develop emission control regulations. As such, air quality models are critical tools for improving air quality, yet they contain large amounts of uncertainty. Developing a constraint on emissions using the 4D-Variational data assimilation technique is one method of reducing the uncertainty in sources of aerosols. In an effort to provide more accurate predictive capabilities the current Community Multiscale Air Quality (CMAQ) adjoint model will be updated to include an adjoint of aerosol dynamics. This will result in the first ever air quality adjoint that includes an adjoint of aerosol size distribution. In order to determine the influences of specific sources of inorganic PM2.5, NOx and NH3 measurements from the OMI and TES instruments aboard the Aura satellite will be assimilated using the 4D-Var method in the CMAQ model.

Adjoint-Based Source Attribution of PM Health Impacts

Long-term exposure to fine particulate matter has been associated with adverse health effects, including premature mortality. In 2011 the World Health Organization estimated that urban outdoor air pollution is the cause of approximately 1.3 million premature deaths worldwide per year. Studies have suggested that PM mixtures with a high BC percentage may have greater effects on mortality than mixtures low in BC. Quantifying the role of emissions from different sectors and different locations in governing the total health impacts is critical towards developing effective control strategies. To answer such questions, an adjoint model can provide sensitivities of excess mortality (through the use of the concentration response functions) with respect to emissions at a highly resolved spatial and sectoral level of specificity. This tool can be used to determine the sensitivity of mortality in a region with respect to emissions throughout the modeled domain. From a single simulation of the CMAQ Adjoint model, we are able to obtain sensitivities of premature mortality due to regional BC concentrations with respect to BC emissions from any and all sectors of the continental United States.

Masters Research

Catalytic Combustion of Small Alcohols on Suspended Sub-Micron and Nano-Size Platinum Particles

Catalysts comprised of nanoparticles can have very high specific surface areas (up to 140m2/g) and have been shown to be significantly more reactive than their bulk-layered counterparts with small alcohols. Experimental results on the effects of particle size and mass loading are reported. Efforts are also underway to develop a computational models based on available gas and surface chemistry mechanisms starting with methanol-air, recognizing however that available surface mechanisms are limited and often validated over a narrow range of parameters, e.g., low pressure. This highlights the need for improved surface mechanisms that are validated over a broad range.

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