Levels of atmospheric carbon monoxide (CO) are declining in the U.S. mid-Atlantic region, according to a new study funded in part by the National Science Foundation (NSF).
Scientists, in a paper published in the September 15 issue of Geophysical Research Letters, compare carbon monoxide concentration levels at Big Meadows in Shenandoah National Park, Virginia. During the periods 1988-1989 and 1994-1997, the researchers report that the annual decrease in carbon monoxide amounts to around five parts per billion by volume (ppbv).
University of Maryland researchers Kristen A. Hallock-Waters, Bruce Doddridge and Russell Dickerson performed the air quality measurements at the Big Meadows site. The site has long been accepted as representative of air quality in the mid-Atlantic region. At an altitude of 1,100 meters (3,609 feet), Big Meadows is removed from local pollution sources.
In addition to carbon monoxide, sampled from a ten-meter (33-foot) tower that extends to slightly above treetop level, the Big Meadows monitoring station observes weather conditions, ultraviolet light penetration, ozone, sulfur dioxide and reactive nitrogen compounds in the air.
The mean level of carbon monoxide at Big Meadows in 1988-1989 was 204 ppbv, as compared with 166 in 1997, a decrease of 4.8 ppbv per year or 22.9 percent total. The carbon monoxide levels are given as annual averages based on hourly samples, as there is considerable fluctuation from hour to hour and month to month.
The researchers attribute the decrease in carbon monoxide largely to reductions in man-made emissions, consistent with trends in emissions reported by other research. Carbon monoxide is a trace pollutant in the troposphere, or lower atmosphere, and is released by the combustion of fossil fuels (such as gasoline) and by biomass burning (such as forest fires). It is an important link controlling the oxidizing capacity of the atmosphere.
The study was also supported by grants from the U.S. Department of the Interior and the Environmental Protection Agency, with additional funding through the Electric Power Research Institute.
Materials provided by National Science Foundation. Note: Content may be edited for style and length.
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