Last Update: April 26, 2007
by: Brad Hall
Current calibration scales for a number of
trace species measured by GML are summarized in the Table. The scales shown
are tied to a specific set of primary standards [Hall et al., 2001] and named
according to the year in which they were adopted. Thus, the preparation and use of new primary
standards for a particular compound results in a new scale for that compound.
Also shown in Table 1 is the number of primary standards used to define
each scale and the concentration range of those standards.
| Species | Previous Scale | Current Scale | Note | N | Range |
|---|---|---|---|---|---|
| N2O | 2000 | 2006A | 1 | 13 | 260-370 ppb |
| SF6 | 2000 | 2006 | 2 | 13 | 0-10 ppt |
| CFC-12 | 2001 | 2008 | 3 | 15 | 150-650 ppt |
| CFC-11 | 1993 | 1992 | 8 | 20-320 ppt | |
| CFC-113 | 2003 | no change | 10 | 20-110 ppt | |
| CH3CCl3 | 2003 | no change | 10 | 10-180 ppt | |
| CCl4 | 1996 | 2008 | 4 | 7 | 25-150 ppt |
| Halon-1211 | 1996 | 2006 | 5 | 5 | 3-7 ppt |
| Halon-1301 | 1990 | 2006 | 6 | 6 | 2-5 ppt |
| HCFC-22 | 1992 | 2006 | 7 | 9 | 75-200 ppt |
| HCFC-141b | 1994 | no change | 3 | 5-50 ppt | |
| HCFC-142b | 1994 | no change | 3 | 5-50 ppt | |
| HCFC-134a | 1995 | no change | 2 | 5-10 ppt | |
| HFC-152a | None | 2004 | 2 | 5-11 ppt | |
| CH3Cl | 2003 | no change | 9 | 280-810 ppt | |
| CH3Br | 2003 | no change | 9 | 8-390 ppt | |
| CHCl3 | 2003 | no change | 1 | 4-13 ppt | |
| CH2Cl2 | 1992 | 2003 | 1 | 6-35 ppt | |
| C2Cl4 | 2003 | no change | 8 | 5-14 ppt | |
| COS | 2002 | 2004 | 8 | 7 | 260-625 ppt |
| CHBr3 | 2003 | no change | 2 | 5-11 ppt | |
| CH2Br2 | 2003 | 2004 | 9 | 2 | 10-20 ppt |
| Benzene | None | 2006 | 2 | 50-100 ppt |
Notes
| 1 | The 2006 N2O scale is 0.19 ppb lower than the 2000 scale at 320 ppb. |
| 2 | The 2006 SF6 scale is 0.033 ppt higher than the 2000 scale at 4 ppt. See scale page for more information |
| 3 | The 2008 CFC12 scale is 1.3% higher than the 2001 scale, see scale page for more information. Update using Y = 1.002*X + 5.807 ppt |
| 4 | Seven standards prepared from 2001-2004 are now used to define te scale. These seven standards are consistent to withoiin 0.5%. Four standards prepared in 1996 have been removed from the scale. For ECD-based results the conversion in 0.9954 at 95 ppt. For GCMS results the conversion is 0.9853. |
| 5 | The 2006 scale is 1% higher than the 1996 scale. The conversion factor is 1.011. |
| 6 | The 2006 halon-1301 scale is 13% higher than the 1996 scale. The conversion factor is 1.13. |
| 7 | Five standards were added to the four than defined the 1992 scale. The 2006 scale is 0.5% higher than the 1992 scale.: Conversion factor 1.005. |
| 8 | Two Aculife-treated standards were replaced by stainless steel standards in 2004. |
| 9 | The scale change is in name only. The original assigment of 2003 was in error. |
Montzka, S.A., J.H. Butler, B.D. Hall, D.J. Mondeel, and J.W. Elkins, 2003, A decline in tropospheric organic bromine, Geophys. Res. Lett., 30(15), 1826, doi:10.1029/2003GL017745.
Hall, B.D., G.S. Dutton, and J.W. Elkins, (2007), The NOAA nitrous oxide standards scale for atmospheric observations, J. Geophys. Res., vol 112, D09035, doi:10.1029/2006JD007954.