Jinbok Lee

Final report on international comparison CCQM-K68: Nitrous oxide in synthetic air

Nitrous oxide (N2O) is one of six greenhouse gases that are regulated by the Kyoto Protocol and has a Global Warming Potential (GWP) that is 296 times that of carbon dioxide. Global levels of nitrous oxide have increased at a rate of 0.25%/yr (0.8 ppb/yr) during the last ten years. In order to monitor levels of nitrous oxide in the atmosphere, it is necessary to use measurement standards with demonstrated equivalence at the highest level of accuracy. This report describes the results of a key comparison of standard gas mixtures of nitrous oxide in synthetic air at an amount fraction of 320 nmol/mol. This key comparison is part of the programme of the Gas Analysis Working Group (GAWG) of the CCQM to demonstrate the equivalence of the standards and measurement capabilities of the NMIs for greenhouse gases. It will support the development of measurement capability at the NMIs for nitrous oxide with uncertainties within the target set by the Global Atmospheric Watch (GAW) programme of the WMO for its global monitoring networks. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Measurement and Characterization of Atmospheric SF 6 at Korea GAW Center in 2007

Korea Global Atmosphere Watch Center (KGAWC), which is located in Anmyeondo and, belongs to the Korea Meteorological Administration (KMA), measures sulfur hexafluoride () in every hour since 2007. In this study, observed in 2007 are discussed. A gas chromatograph-electron capture detector (GC-ECD) with pre-cooled device is applied during the observation, and produced data are qualified by means of periodic calibration with standard gas made by Korea Research Institute of Standard and Science (KRISS). has been greatly paid attention since Kyoto protocol because of its high global warming potential(GWP) with 22,200 times of in the period of 100 years. It is a man-made compound and has been usually used for gas insulation since 1970s and for etching process in the information technology-based industry since 1990. Average mixing ratio of in 2007 was 6.65 pmol/mol at Anmyeondo. According to the GAW report published in 2008, average mixing ratio of in the atmosphere is continuously growing. At present, the average mixing ratio of in the atmosphere is known to be approximately 6.25 pmol/mol at global observatory. value in Anmyeondo shows 0.40 pmol/mol greater than that of the Mauna Loa observatory in 2007.

Validation of spectroscopic gas analyzer accuracy using gravimetric standard gas mixtures: Impact of background gas composition on CO 2 quantitation by cavity ring-down spectroscopy

The effect of background gas composition on the measurement of CO2 levels was investigated by wavelengthscanned cavity ring-down spectrometry (WS-CRDS) employing a spectral line centered at the R(1) of the (3 00 1)III← (0 0 0) band. For this purpose, eight cylinders with various gas compositions were gravimetrically and volumetrically prepared within 2σ = 0.1 %, and these gas mixtures were introduced into the WS-CRDS analyzer calibrated against standards of ambient air composition. Depending on the gas composition, deviations between CRDSdetermined and gravimetrically (or volumetrically) assigned CO2 concentrations ranged from −9.77 to 5.36 μmol mol−1, e.g., excess N2 exhibited a negative deviation, whereas excess Ar showed a positive one. The total pressure broadening coefficients (TPBCs) obtained from the composition of N2, O2, and Ar thoroughly corrected the deviations up to −0.5 to 0.6 μmol mol−1, while these values were −0.43 to 1.43 μmol mol−1 considering PBCs induced by only N2. The use of TPBC enhanced deviations to be corrected to ∼ 0.15 %. Furthermore, the above correction linearly shifted CRDS responses for a large extent of TPBCs ranging from 0.065 to 0.081 cm−1 atm−1. Thus, accurate measurements using optical intensity-based techniques such as WS-CRDS require TPBC-based instrument calibration or use standards prepared in the same background composition of ambient air.

Gravimetric standard gas mixtures for global monitoring of atmospheric SF6

In this study, standard gas mixtures of SF6 in synthetic air were gravimetrically developed as a suite consisting of 6 mixtures with mole fractions of SF6 ranging from 5 to 15 pmol/mol. For precision in weighing the gas fills, an automatic weighing system coupled with a high sensitivity mass balance was used and a gravimetry precision of 3 mg (2σ) was achieved. Impurity profiles of the raw gases were determined by various analyzers. In particular, sub pmol/mol levels of SF6 in the matrix components (N2, O2, and Ar) were carefully measured, since the mole fraction of SF6 in the final step can be significantly biased by this trace amount of SF6 in the raw gases of the matrix components. Gravimetric dilution of SF6 by purity-assessed N2 was performed in 6 steps to achieve a mole fraction of 440 pmol/mol. In the final step, O2 and Ar were added to mimic the atmospheric composition. Gravimetric fractions of SF6 and the associated standard uncertainty in each step were computed according to the ISO 6142 and JCGM 100:2008, respectively, and validated experimentally. Eventually, the SF6 fraction uncertainty of the standard gas mixtures combined by uncertainties of gravimetric preparation and verification measurements were found to be nominally 0.08% at a 95% confidence interval. A comparison with independent calibration standards from NOAA shows agreement within 0.49%, satisfying the extended WMO compatibility goal, 0.05 ppt.

Final report of key comparison APMP.QM-K53—comparison of gravimetric preparative capability with 100 μmol/mol of oxygen in nitrogen (bilateral comparison between NIM and KRISS)

This bilateral comparison, which is traceable to CCQM-K53, was carried out to support NIMs capability for the preparation of stable gas species in nitrogen. The target amount of substance was 100 μmol/mol of oxygen in nitrogen, which was prepared gravimetrically by the participant. The comparison showed that the NIM and KRISS gravimetric values were consistent with each other to within the expanded uncertainty of 0.200 μmol/mol. Therefore the comparison is well linked to the CCQM-K53 and offers a gravimetric preparation capability of oxygen in nitrogen at a level of 100 μmol/mol to the participant. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Final report on international comparison CCQM-K83: Halocarbons in dry whole air

The growing awareness of climate change/global warming and continuing concerns regarding stratospheric ozone depletion will require future 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. This report describes the results of a key comparison for several of the more important halocarbons at atmospheric concentration levels. The comparison includes 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 the measurement capabilities of the participants for these halocarbons at trace atmospheric levels. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).