Current Projects

	Environmental Impacts of Nanotechnology. Nanotechnology brings the promise of improved medical imaging, thin display screens, and clean energy. Although the growth of the nanotechnology industry has been breathtakingly rapid, very little is known about the environmental effects of manufactured nanomaterials. The overall objective of this research is to conduct a cross-media assessment of the transport, transformation, and fate of manufactured nanomaterials in atmospheric, aquatic, and terrestrial environments. This video on YouTube describes the project in lay terms. We are also a key participant in the National Science Foundation-sponsored Center for the Environmental Impacts of Nanotechnology.
	Measurement of Air Pollutant Emissions at the Neighborhood Scale. One of the largest uncertainties in our ability to manage air quality is the magnitude of emissions. Independent estimates have suggested that official inventories may be off by factors of 10 or more. We have developed a mobile platform, the Flux Laboratory for the Atmospheric Measurement of Emissions (FLAME), that uses eddy covariance to measure emissions of carbon dioxide, nitrogen oxides, volatile organic compounds, and fine particulate matter. So far, we have conducted field campaigns in a small Appalachian town dominated by coal transport near the corner of Kentucky, Ohio, and West Virginia; at 16 sites in Norfolk, Virginia; and at three schools in Roanoke, Virginia.
	Air Quality in Mexico. Air pollutant emissions, transport, and impacts in the US-Mexico border region are a complex problem because of rapid population and industrial growth and national differences. In 2010, we participated in the Cal-Mex field study in Tijuana to characterize emissions and their impacts on local and regional air quality, human health, and climate change. Mexico City is one of the most polluted cities in the world and has been the focus of a case study on air pollution in megacities. During the MIRAGE field campaign in 2006, we measured polycyclic aromatic hydrocarbons (PAHs), which are important because of their potent mutagenicity and carcinogenicity, and reported on their sources and transformations in the atmosphere.
	Influenza Bioaerosols. We are applying engineering tools to study the dynamics of influenza viruses in the atmosphere. The importance of influenza transmission via the aerosol route remains contentious, and our recent publication in the Journal of the Royal Society Interface on measurements in a health care facility, a day care center, and on airplanes has shown that it is indeed possible.

Completed Projects

	Ammonia Emissions from Agriculture. Not only is ammonia a toxic gas, but it is also a key component of particle formation in the atmosphere. These particles endanger our health, degrade visibility, affect global climate change. Although agriculture is responsible for 90% of ammonia emissions, the understanding of such emissions is limited. The objective of this project is to quantify the emissions from cow manure during different stages of the storage and treatment process. The amount of nitrogen in the cows' diets will be manipulated in attempt to minimize ammonia emissions.
	Air Quality Modeling. Three-dimensional chemical transport models can be used to understand the relationships between emissions, chemistry, and meteorology in producing certain concentrations of pollutants. Models can also be used to optimize airshed management strategies. We worked with local governments in the Shenandoah Valley to help this area meet its air quality goals.
	Sustainable Mobility. Sustainable mobility is a concept intended to describe ways of moving people and goods around while eliminating the ensuing environmental damage caused by vehicles and infrastructure. In addition to consuming enormous amounts of resources and seriously degrading air quality, transportation also exacerbates many environmental and societal problems, such as water pollution, noise, erosion, and traffic. We have developed the Sustainable Mobility Lab to provide students and researchers with an interdisciplinary introduction to sustainable mobility.
	Naphthalene Volatilization at a Phytoremediation Site. Phytoremediation is used to enhance the removal of groundwater contaminants. We are finding that trees enhance not only biodegradation and groundwater transport, but also the volatilization of contaminants directly out of the ground and into the atmosphere. Here, graduate student Claire Booth pounds out her frustrations and installs a flux chamber at a creosote-contaminated site in Tennessee.
	PAH Exposure. In October 2002, we collaborated with a team from the Harvard School of Public Health to measure exposure to particles in diesel trucking terminals in Mexico City. We measured PM2.5, particulate polycyclic aromatic hydrocarbons (PAHs), aerosol active surface area, elemental and organic carbon, and detailed particle speciation in loading dock areas and in delivery trucks driving throughout the city.
	Weekend Ozone Effect. Although emissions of ozone precursors are typically lower on weekends, ozone concentrations are higher on weekends in some urban areas. In this work, a combination of data analysis, emission inventory development, and photochemical modeling on multiple time scales shows how photochemical air pollution responds to changes in precursor emissions on daily, weekly, and decadal time scales. Changes in ozone sensitivity, combined with the increased contribution of heavy-duty diesel trucks to the emission inventory and correspondingly larger weekday-weekend difference in NOx emissions, explains why the weekend ozone effect has spread throughout California between 1980 and the present.

Unsupported Projects

Bullfighting. During a field campaign in Mexico City in 2003, I tried my hand at bullfighting. I earned a nice bruise and learned that I should stick to academic pursuits.

Sliced Bread: Even or Odd? While on a ski trip in Colorado in 2002, I hypothesized that bags of bread contained an even number of slices. Then, the buyer could make sandwiches and not be left with an extra slice. At the City Market in Dillon, three of us counted the number of slices in 10 randomly selected bags of bread. Our preliminary results found that 60-70% of bags had an even number of slices.