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Oct 22, 2022 148 likes •275 views

Gaseous reference materials to underpin measurements of amount fraction and isotopic composition of greenhouse gases Paul Brewer NOAA ESRL Global Monitoring Annual Conference 23 rd May 2017 Rationale Requirement for traceability from the

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Gaseous reference materials to underpin measurements of amount fraction and isotopic composition of greenhouse gases

Paul Brewer

NOAA ESRL Global Monitoring Annual Conference 23rd May 2017

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Rationale

  • Requirement for traceability from the primary realisation of the mole
  • Legislation aimed at reducing emissions and their measurement
  • Long-term observations based on accurate and stable standards

1 2 3 4 5 6 7 8 9 10 300 320 340 360 380 400 420 440 1920 1950 1980 2010 Population (billion) Carbon Dioxide (parts per million) carbon emissions (billion tons per year)

400 ± 0.05 µmol/mol 400 ± 0.10 µmol/mol 325 ± 0.1 nmol/mol 1800 ± 2 nmol/mol 7 ± 0.02 pmol/mol 300 ± 2 nmol/mol 0.025 % 0.031 % 0.10 % 0.67 %

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Comparability

CO2 2006 CH4 2003 2013

  • Isotopic composition of 12CO2 - 13CO2

matched to natural abundance

  • Uncertainty < 0.05 % for CO2 and < 0.1

% for CH4 (k=1)

CO2 2013

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Synthetic Reference Standards

  • Gravimetric preparation
  • Purity analysis
  • Analytical validation

Challenges Purity and gravimetry Stability Commutability

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Purity and gravimetry

  • New method with lower uncertainty
  • NPL Adjustable Gas Standard
  • Quantification by standard addition
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Stability

weeks

10 20 30

amount fraction change (µmol/mol)

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Commutability

  • H. Nara, H. Tanimoto, Y. Tohjima, H. Mukai, Y. Nojiri, K. Katsumata and C. W. Rella, Atmos. Meas. Tech., 5, 2689–2701, (2012).
  • Influence of matrix composition
  • n spectroscopy (requirement

for 0.1 cmol mol-1)

  • More pronounced for CO2

1 ‰ corresponds to ~ 4 nmol/mol

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fermentation combustion natural gas NPL blend

Commutability

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Calibration

626 636 628 628 628

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Influence of the calibration

F

  • 11 ‰

B

  • 5 ‰

W

  • 1 ‰

C

  • 35 ‰
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Metrology for Stable Isotope Reference Standards (SIRS)

The project will address:

  • Limitations in infrastructure to deliver international gaseous CO2 reference materials
  • Absence of international gaseous N2O reference materials with stated uncertainties
  • Advances in optical spectroscopy for traceable field deployable techniques

New reference materials, calibration methods and instrumentation

  • CO2 (pure and 400 µmol/mol in air, uncertainties: δ13C-CO2 0.1 ‰, δ18O-CO2 0.5 ‰)
  • Re-measure absolute CO2 isotope ratios to provide data for SI traceability
  • N2O (pure and 300 – 1000 nmol/mol in air)

reference materials (uncertainties 1.0 ‰ (δ15Nα and δ15Nβ) and 0.5 ‰ (δ15N, δ18O))

  • Spectroscopic

methods for isotope ratio measurements

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Conclusions

  • Substantial progress made towards developing an infrastructure to provide SI traceability for

measurements of CO2, CH4, N2O and CO

  • Research required to deliver gaseous reference materials for isotope ratio of CO2 and N2O

Acknowledgements