SST emissions cut stratospheric ozone.Responding to NASA's proposal to put 500 new high-speed civil transport (HSCT HSCT Hematopoietic Stem Cell Transplant HSCT High Speed Civil Transport HSCT High School Competency Test HSCT Hypersonic Commercial Transport HSCT Hygiène Sécurité Conditions de Travail en Collectivité Territoriale HSCT Hayling Sentence Completion Task ) planes into service by 2015, scientists have been estimating the potential impact of routine supersonic flight on Earth's stratospheric ozone (SN: 10/22/94, p.260). Now they have some hard data. David W. Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration Noun 1. National Oceanic and Atmospheric Administration - an agency in the Department of Commerce that maps the oceans and conserves their living resources; predicts changes to the earth's environment; provides weather reports and forecasts floods and hurricanes and in Boulder, Colo., and his colleagues have measured exhaust emissions from a Concorde supersonic transport (SST SST: see airplane. ) plane during high-altitude flight. Traversing the exhaust trail of a Concorde 11 times during an Air France flight from Fiji to New Zealand New Zealand (zē`lənd), island country (2005 est. pop. 4,035,000), 104,454 sq mi (270,534 sq km), in the S Pacific Ocean, over 1,000 mi (1,600 km) SE of Australia. The capital is Wellington; the largest city and leading port is Auckland. last year, a NASA NASA: see National Aeronautics and Space Administration. NASA in full National Aeronautics and Space Administration Independent U.S. environmental research plane sampled the SST's exhaust, the researchers report in the Oct. 6 Science. The Concorde flew at 53,000 feet and at twice the speed of sound. The scientists measured 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. , water vapor, reactive nitrogen and hydrogen, and sulfurous sul·fur·ous adj. 1. Of, relating to, derived from, or containing sulfur, especially with valence 4. 2. Characteristic of or emanating from burning sulfur. particles in the exhaust, finding more small particles than expected. The particles' abundance and size indicates that "sulfuric acid is produced from fuel sulfur more efficiently than expected after emission from the engine," Fahey's team says. "If a fleet of HSCT aircraft produces particles at a rate comparable to that of the Concorde, increases in particle number and surface area would occur throughout the lower stratosphere in the Northern Hemisphere," they add. If future planes emit larger than expected numbers of particles, they assert, their exhaust will have a correspondingly greater impact on stratospheric ozone. The researchers also observe that to lessen the exhaust particles' ozone-damaging impact, the sulfur concentrations of jet fuel may need to be "controlled to lower values." While saying that this study demonstrates "good science and operations," Howard L. Wesoky, an aeronautical engineer at NASA in Washington, D.C., nevertheless adds that its significance is "not yet clear. "This study is only one of many we're performing to understand how high-speed aircraft emissions react chemically and affect the stratosphere." Using data from NASA's projections for high-speed flight in 2015, Debra K. Weisenstein, a researcher at Atmospheric and Environmental Research in Cambridge, Mass., found that additional exhaust particles could deplete de·plete v. 1. To use up something, such as a nutrient. 2. To empty something out, as the body of electrolytes. stratospheric ozone by as much as 1 percent. "It's safe to say that these results come from a state-of-the-art model," she says. "That's significant." -- |
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