the laboratory, the scientists dried samples of corn leaves and husks, then converted them to graphite using a series of chemical reactions. The graphite then was analyzed in the W.M. Keck Carbon Cycle Accelerator Mass Spectrometer, which measures a rare isotope of carbon, called radiocarbon. Carbon dioxide derived from fossil fuels contains no radiocarbon so it is easily distinguishable from other sources. With measurements from this machine, scientists calculated overall levels of carbon dioxide produced by fossil fuels at the location where the corn samples were collected.
California and the Ohio Valley had the most fossil-fuel-emitted carbon dioxide, while the Colorado region had the least. The scientists expected pollution from California and other western coastal states to drift east, but they found that the Rocky Mountains appeared to provide a barrier for the movement of carbon dioxide from fossil fuels.
Air in the Mountain West, including Colorado, Idaho and New Mexico, was the cleanest, with about 370 parts per million of carbon dioxide. Air in the Eastern United States, which includes Massachusetts, New Hampshire and New York, contained an additional 2.7 parts per million of carbon dioxide from fossil fuel sources. Air in Maryland, Ohio, Pennsylvania and West Virginia had nearly twice as much additional carbon dioxide from fossil fuels, 4.3 parts per million.
"We have to better understand emission patterns and changes in the atmosphere in order to better regulate fossil fuels," said Susan Trumbore, also a professor of Earth system science and co-author of the study. "This is a direct way to measure the release of carbon dioxide emissions that are contributing to climate warming." Page: 1 2 Related biology news :1
Source:University of California - Irvine
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