Comparison of halocarbon measurements in an atmospheric dry whole air sample
George C. Rhoderick, Bradley Hall, Christina Harth, Jin Seog Kim, Jeogsoon Lee, Stephen Montzka, J. Muhle, Stefan Reimann, Martin Vollmer, Ray Weiss
The growing awareness of climate change/global warming, and continuing concerns regarding stratospheric ozone depletion, will require continued measurements and standards for many compounds, in particular halocarbons that are linked to these issues. In order to track and control the emissions of these species globally in the atmosphere, it is necessary to demonstrate measurement equivalence at the highest levels of accuracy for assigned values of standards. Precise measurements of these species aid in determining small changes in their atmospheric abundance. A common source of standards/scales and/or well documented agreement of different scales used to calibrate the measurement instrumentation are key to understanding many sets of data reported by researchers. This report describes the results of a comparison study between National Metrology Institutes and atmospheric research laboratories for several of the chlorofluorocarbons (CFCs); dichlorodifluoromethane (CFC 12), trichlorofluoromethane (CFC 11), and 1,1,2 trichlorotrifluoroethane (CFC 113); the hydrochlorofluorocarbons (HCFCs); chlorodifluoromethane (HCFC 22) and 1-chloro-1,1,-difluoroethane (HCFC 142b), and the hydrofluorocarbon (HFC); 1,1,1,2 tetrafluoroethane (HFC 134a), all in a dried whole air sample. The objective of this key comparison is to compare calibration standards/scales and the measurement capabilities of the participants for these halocarbons at trace atmospheric levels. Results of this study show agreement between these different scales to better than 2.5 % in almost all cases, with many of the reported agreements being better than 1.0 %.