Atmospheric Moisture Sampling

Two atmospheric moisture samples were obtained from the Blackfoot CMS location, two from Atomic City, one from Idaho Falls, and one from Rexburg CMS during the first quarter, 2001.  Atmospheric moisture was collected by continuously drawing air through a column of silica gel that absorbed water vapor.  Each sample was collected after 4-13 weeks, depending on when an adequate amount of moisture had been extracted by the silica gel from the atmosphere.  The water was then extracted from the silica gel by distillation.  The resulting atmospheric moisture samples were analyzed for tritium using liquid scintillation. 

All six atmospheric moisture samples had tritium results greater than their 2s uncertainty and MDC.  It is important to note that sample blanks (submitted as part of normal QA/QC procedures) for precipitation sampling, analyzed with the same instrumentation as the atmospheric moisture samples, also had results greater than their associated 2s uncertainties and MDCs.  Therefore, there is a high probability that one or more of the atmospheric moisture sample results were false positives (see the Confidence in Detections section in the Helpful Information section of this report).  However, even with this potential bias, the concentrations were very low.  For comparison, the DCG value for tritium in air (as atmospheric moisture) is 1 x 10^-7 µCi/mL (3.7 x 10^-3 Bq/mL) (Appendix B).  Tritium results measured at these locations during the first quarter of 2001 were between 100,000 to nearly 800,000 times lower than this limit.  Tritium results for all atmospheric moisture samples are listed in Table C-4 (Appendix C).   

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