Corn, a new sensor of carbon dioxide.Scientists have developed a way to use corn plants to monitor and map the human-generated emissions of carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. . Only a small fraction of Earth's atmosphere is carbon dioxide. In summer 2004, that share averaged about 378 parts per million parts per million mg/kg or ml/l; see ppm. (ppm), says James T. Randerson, a biogeochemist at the University of California The University of California has a combined student body of more than 191,000 students, over 1,340,000 living alumni, and a combined systemwide and campus endowment of just over $7.3 billion (8th largest in the United States). , Irvine. Within that component, about one in a trillion of the carbon atoms is carbon-14 (C-14), a radioactive isotope radioactive isotope or radioisotope, natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached. produced by cosmic rays cosmic rays, charged particles moving at nearly the speed of light reaching the earth from outer space. Primary cosmic rays consist mostly of protons (nuclei of hydrogen atoms), some alpha particles (helium nuclei), and lesser amounts of nuclei of carbon, nitrogen, at high altitudes. However, the carbon dioxide produced by burning fossil fuels has no C-14. That's because the isotope decays to undetectable concentrations after about 50,000 years, and fossil fuels derive from organic material much older than that. By measuring the proportion of C-14 in corn plants, Randerson and his colleagues can determine the mix of naturally occurring and fossil fuel-generated carbon dioxide that the plants absorbed as they grew. Some of the highest concentrations of C14 in North America--and therefore the least carbon from fossil fuels--appeared in corn grown at a site in northern California where prevailing winds blow relatively unpolluted air off the ocean. The team's analysis suggests that the air in Brentwood, Calif., downwind of the San Francisco area, had about 11 ppm excess carbon dioxide attributable to fossil fuels, the researchers report in the Jan. 28 Geophysical Research Letters Geophysical Research Letters is a publication of the American Geophysical Union. GRL is the organization's only letters journal. Since its introduction in 1974, GRL has published only short research letters, typically 3-5 pages long, which focus on a specific discipline or . Surprisingly, says Randerson, the atmosphere at sites in the eastern portions of the Rocky Mountains didn't contain much carbon dioxide from fossil fuels. However, 34 sites east of the Mississippi River averaged about 2.7 ppm extra carbon dioxide. Researchers could use the team's results, as well as similar studies, to improve their models of large-scale air movements across North America, Randerson's team asserts. |
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