An International Marine-Atmospheric222Rn Measurement Intercomparison in Bermuda Part I: NIST Calibration and Methodology for Standardized Sample Additions.
As part of an international222Rn measurement intercomparison conducted at Bermuda in October 1991, NIST provided standardized sample additions of known, but undisclosed ("blind")222Rn concentrations that could be related to U.S. national standards. The standardized sample additions were obtained with a calibrated226Ra source and a specially-designed manifold used to obtain well-known dilution factors from simultaneous flow-rate measurements. The additions were introduced over sampling periods of several hours (typically 4 h) into a common streamline on a sampling tower used by the participating laboratories for their measurements. The standardized222Rn activity concentrations for the intercomparison ranged from approximately 2.5 Bq · m-3to 35 Bq · m-3(of which the lower end of this range approached concentration levels for ambient Bermudian air) and had overall uncertainties, approximating a 3 standard deviation uncertainty interval, of about 6 % to 13 %. This paper describes the calibration and methodology for the standardized sample additions.
National Institute of Standards and Technology, Gaithersburg, MD 20899-0001 USA.
R
R
Collé
National Institute of Standards and Technology, Gaithersburg, MD 20899-0001 USA.
M P
MP
Unterweger
National Institute of Standards and Technology, Gaithersburg, MD 20899-0001 USA.
P A
PA
Hodge
National Institute of Standards and Technology, Gaithersburg, MD 20899-0001 USA.
J M R
JM
Hutchinson
calibration; environment; intercomparison; marine atmosphere; measurement; radium-226; radon-222; standards