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Title:  Atmospheric Carbon Monoxide Levels Decline in U.S. Mid-Atlantic
          Region
Date:   September 10, 1999



  Media contact:
  September 10, 1999
  Cheryl Dybas
  NSF PR 99-52
  (703) 306-1070/cdybas@nsf.gov

                 ATMOSPHERIC CARBON MONOXIDE LEVELS DECLINE IN U.S.
  MID-ATLANTIC REGION

       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 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.

  -NSF-