Scientists at the University of Miami Rosenstiel School of Marine & Atmospheric Science discovered a technique to track urban atmospheric plumes thanks to a unique isotopic signature found in vehicle emissions. The team discovered that ethanol mixed in vehicle fuel is not completely burned, and that ethanol released in the engine’s exhaust has a higher 13C to 12C ratio when compared to natural emissions from most living plants. In other words, the corn and sugarcane used to make biofuels impart a unique chemical signature that is related to the way these plants photosynthesize their nutrients. Ethanol’s unique chemical signature can now be used during aircraft sampling campaigns to identify and track plumes as they drift away from urban areas. Air collected and analyzed from downtown Miami and the Everglades National Park and found that 75% of ethanol in Miami’s urban air came from manmade biofuels, while the majority of ethanol in the Everglades air was emitted from plants, even though a small quantity of city pollution from a nearby road floats into the park. Credit: UM/RSMAS
Scientists have discovered a technique to track urban atmospheric plumes, thanks to a unique isotopic signature found in vehicle emissions. Brian Giebel, a marine and atmospheric chemistry graduate student working with University of Miami researchers Daniel Riemer and Peter Swart, discovered that ethanol mixed in vehicle fuel is not completely burned, and that ethanol released in the engine's exhaust has a higher 13C to 12C ratio when compared to natural emissions from most living plants. In other words, the corn and sugarcane used to make biofuels impart a unique chemical signature that is related to the way these plants photosynthesize their nutrients. The team suggests that ethanol's unique chemical signature can be used during aircraft sampling campaigns to identify and track plumes as they drift away from urban areas. Their study, titled 'New Insights to the Use of Ethanol in Automotive Fuels: A Stable Isotopic Tracer for Fossil- and Bio-Fuel Combustion Inputs to the Atmosphere,' appears in the journal Environmental Science & Technology. Giebel collected and analyzed air from downtown Miami and Everglades National Park, finding that 75 percent of ethanol in Miami's urban air came from manmade biofuels, while the majority of ethanol in the Everglades air was emitted from plants, even though a small quantity of city pollution from a nearby road floats into the park. Air samples from the two locations were subjected to a precise scientific process, first separating the elements using gas chromatography and then burning each component.
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