NSF PR 99-52 - September 10, 1999
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Atmospheric Carbon Monoxide Levels Decline in U.S.
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
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
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 midAtlantic 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.