Isotope Technique Distinguishes Emitted Ethanol "Signatures" from Tropical Plants and from Vehicle Exhausts

Scientists from the University of Miami Rosenstiel School of Marine & Atmospheric Science (United States) report the use of stable isotopic ratio measurements of carbon-13 to carbon-12 to detect and distinguish ethanol from automotive exhausts and biogenic ethanol emissions from tropical plants. Unburned biofuel ethanol in vehicles can be emitted into the atmosphere and can have potential impacts on air quality. At the same time, "natural ethanol emissions" are said to exist in living plants.

The researchers discovered that unique "ethanol signatures" from these emissions can be distinguished by looking at the ratio of carbon-13 to carbon-12 isotopes in the samples. They report that "ethanol emitted in exhaust is distinctly different from that emitted by tropical plants and can serve as a unique stable isotopic tracer for transportation-related inputs to the atmosphere". When they used the technique to analyze air samples in downtown Miami and the Everglades National Park, they found "that 75% of ethanol in Miami's urban air came from synthetic 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". One possible application of the technique, as suggested by the research team would be during aircraft sampling campaigns to identify and track plumes as they drift away from urban areas." The complete paper is published in the journal, Environmental Science and Technology (URL above).