NOAA/CMDL Firn Air Measurements of Halogenated Gases

Data placed in this directory are NOAA/CMDL measurements of 
halogenated gases in firn air at South Pole, Antarctica (1995); Tunu, 
Greenland (1996); and Siple Dome, Antarctica (1997).  Analyses of these 
measurements have been published in the following paper:

Butler J. H., Battle M., Bender M., Montzka S. A., Clarke A. D., Saltzman 
E. S., Sucher C., Severinghaus J., and Elkins J. W. (1999) A  record of 
atmospheric halocarbon concentrations during the twentieth century from 
polar firn air. Nature 399, 749-755.


The data in this directory are organized by analytical instrument.  OTTO is 
a three-channel, isothermal, packed column gas chromatograph with 
electron-capture detection (GC/ECD) that injects air samples directly.  
LEAPS is also a GC/ECD, but with a capillary column, temperature 
programmed oven, and injection of cryotrapped air.  GCMS refers to the 
gas chromatographs with mass spectrometric detection, which also have 
capillary columns, temperature programming, and injection of cryotrapped 
air.  

Because contamination of the extremely low level samples is a concern in 
the sampling and analysis of firn air, means of paired flasks or even means 
of measurements on single flasks do not always tell the whole story.  
Consequently, the data presented here include individual measurements, 
flask averages, and averages for each depth sampled.  Glass and steel flasks 
were used for many analyses and the data have been included for both 
whenever this was possible.  Limited amounts of air precluded analysis of 
the glass flasks by GCMS.

Anyone is welcome to download these data and work with them.  If using 
the data in a presentation or a publication, the source of these data should 
be acknowledged and appropriate references cited.  We prefer that you 
contact Dr. James Butler (jbutler@cmdl.noaa.gov, 303-497-6898), Dr. 
Stephen Montzka (smontzka@cmdl.noaa.gov, 303-497-6657), or Dr. 
James Elkins  (jelkins@cmdl.noaa.gov, 303-497-6224) before using these 
data in any publication.

Other firn air data will be made available at this ftp site as they are 
published. N2O, CO2, and CH4 data from these sites, and in partial 
support of an earlier publication, will appear on this site soon.  That 
publication is

Battle M., Bender M., Sowers T., Tans P., Butler J., Elkins J., Ellis J., 
Conway T., Zhang N., Lang P., and Clarke A. (1996) Histories of 
atmospheric gases from the firn at South Pole. Nature 383(6597), 231-235.