RUI: Impact of Changing Fuel Usage on the Atmospheric Cycling of Ethanol, Optically Active Organic Compounds and Iron (Fe) in Rainwater

University Of North Carolina At Wilmington, Wilmington NC

Investigators

Abstract

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.