The overarching goal of the research is to delineate potential impacts of current and future fossil fuel usage and emission changes on the chemistry of the troposphere. The first objective explores the link between increased ethanol production and use to possible increased levels of ethanol and volatile organic carbon compounds in precipitation. The first detailed seasonal and temporal profile of ethanol concentrations in rainwater will be developed with an emphasis on the influence of air mass origin on concentrations. Rainwater will be collected in Wilmington, NC and in São Paolo, Brazil where ethanol makes up 40% of vehicle fuel. This comparison will provide a unique and novel opportunity to examine how shifting ethanol usage in North America could ultimately impact the chemistry of the troposphere. The second objective examines how fossil fuel emissions from various combustion sources including 85% ethanol vehicle fuel (E85), gasoline and diesel fuels as well as coal and fuel oil combustion impact the abundance of light absorbing or chromophoric dissolved organic material (CDOM) in rainwater. Specific questions to be addressed involve determining the chemical composition of CDOM produced from various fuel sources initially and as a function of irradiation time in comparison to changes observed in analogous rainwater samples. The final objective of the research explores the relationship between fossil fuel emissions and the speciation of iron in atmospheric waters. Preliminary evidence suggests the chromophoric material in rainwater contains ligand(s) of fossil fuel origin that stabilize Fe(II) allowing significant concentrations to occur in precipitation even in the presence of micromolar concentrations of the oxidant hydrogen peroxide. Recent data suggest that the abundance of these ligands is changing over time in rainwater although it is unclear why. This phase of the research will determine if DOM obtained from various fuel sources is capable of binding Fe(II) and Fe(III) and whether the abundance of these ligands is changing.
Exploring the importance of shifting fuel usage on the composition of the troposphere is central to the understanding of a host of current as well as future atmospheric processes as the quantity and quality of fuel used in energy production changes. Results of this research will have important implications for global climate change because chromophoric material directly influences the spectral attenuation of sunlight reaching the earth's surface. An additional consequence of the production of chromophoric material in rainwater from combustion sources is the potential impact on the oxidizing capacity of the troposphere by generating significant quantities of aqueous phase hydrogen peroxide. Addressing the redox chemistry of iron is important because any change in iron speciation affects the lifetime and bioavailability of iron as a nutrient, which in turn will alter the rate of marine primary productivity. Marine primary productivity is known to play a significant role in removal of carbon dioxide from the atmosphere and hence impacts the magnitude of global warming. The project will support a post-doctoral researcher, two master's level graduate students, three undergraduates and one high school student per year. Young students are attracted to this type of study because they perform high profile environmental research of international interest. This ultimately motivates them to continue their education and choose a career in science which enhances the recruiting and retaining of young students in critical STEM fields.
The goal of this research was to explore the impacts of current and future use of ethanol as a fuel on the chemistry of the lower atmosphere as reflected by rainwater composition. Ethanol has been added to gasoline to help it burn cleaner, reduce the emissions of carbon dioxide, and decrease our dependence on foreign oil. However, some of the ethanol is not combusted and is emitted directly from the exhaust of gasoline engines. In addition to a variety of impacts ethanol can have on atmospheric chemistry, one important impact is on the production of smog. In countries like Brazil, where ethanol is used to a greater extent than the United States, there are significant air pollution problems. The first step of our study was to develop a method to determine low concentrations of ethanol in rain because no analysis existed prior to this research. We collected precipitation samples at our location in Wilmington NC as well as in Brazil with the help of a collaboration established prior to the onset of this study. Rainwater concentrations determined during this research are noteworthy because they are the first to shed light on the amount of ethanol currently in the atmosphere. Significant levels of this chemically reactive alcohol were present in every rain sample analyzed. Concentrations were an order of magnitude higher in São Paulo Brazil where ethanol makes up approximately one half of automotive fuel compared to Wilmington, NC USA where gasoline contains approximately 10 percent ethanol. Comparison of future ethanol concentrations to data collected during this study will help delineate potential consequences of this reactive compound especially if the United States transitions to more alcohol blended fuels. The oceans contain very small plants known as phytoplankton that are capable of removing large amounts of carbon dioxide from the atmosphere. This is important because it suggests that phytoplankton play a central role in the elimination of this potent greenhouse gas with important consequences for global warming and climate change. The abundance of marine phytoplankton is very often limited by the availability of iron as a nutrient. Iron occurs in different forms and only one form (FeII) can be used by phytoplankton for growth. Under the chemical conditions found in ocean water, this form of iron is not stable and is converted rapidly to an unusable species. Our laboratory has found that iron in rainwater is stabilized in the form phytoplankton can use by entities created during the combustion of gasoline and coal. Our results with automobile exhaust collected from 13 different vehicles indicate that older, high mileage vehicles produce compounds that stabilize FeII and prevent it from oxidizing. Coal combustion exhaust can also stabilize FeII. Therefore as the US transitions away from coal to natural gas for power production, and cars use better emission control technology, there will be a decrease in FeII in rainwater. These results are significant because any change in FeII caused by changing fossil fuel usage could alter the ocean’s ability to remove carbon dioxide from the atmosphere which has important ramifications for global climate change. This project has provided a unique educational opportunity for a large number of undergraduate students, master's students, three post-doctoral fellows, one high school student and one current high school chemistry teacher. The data generated has also afforded environmentally relevant examples of cutting edge science of international interest for several undergraduate and graduate chemistry and marine science courses at UNCW. Young students are attracted to this type of study because they perform environmental research of global international interest. The success of our commitment to getting students excited about science as a career by bringing high profile research into the classroom is borne out in a recent issue of Chemical and Engineering News in which this department ranked in the top 3% nationally in the number of American Chemical Society certified BS chemistry degrees awarded Finally, our research on possible impacts of changing ethanol and fossil fuel use has stimulated many discussions (often energetic and sometimes heated) about sustainability in energy production for the US. These discussions occur among our students in our research labs and in our classrooms. This complicated topic causes students to consider the whole energy picture going well beyond air quality to food production and political instability. Energy sustainability will be a topic of great importance for the next several decades so it is of paramount importance for students to have these discussions now weighing the pros and cons of future global energy production processes.
