Development of a southern oceanic air standard reference material

Area of Science:

• Atmospheric chemistry and metrology
• Climate change research
• Gas mixture analysis

Background:

• The U.S. Congress tasked NIST with supporting climate change research in 2009.
• NIST's Gas Sensing Metrology Group develops standard gas mixtures for atmospheric measurements.
• Greenhouse gases like CO2, CH4, and N2O are critical for climate monitoring.

Purpose of the Study:

• To create primary standard mixtures (PSMs) for key greenhouse gases.
• To certify a new Standard Reference Material (SRM) of southern oceanic air.
• To achieve the lowest measurement uncertainties for gas SRMs.

Main Methods:

• Gravimetric preparation of primary standard mixtures (PSMs) for CO2, CH4, and N2O.
• Collection of pristine southern oceanic air samples at Baring Head, New Zealand.
• Spectroscopic analysis of gas mixtures and calibration using PSMs.

Main Results:

• Developed PSMs for carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).
• Created NIST SRM 1721 Southern Oceanic Air, certified for ambient mole fractions.
• Achieved relative expanded uncertainties of no larger than 0.06% for certified values.

Conclusions:

• NIST has established new, highly accurate gas standards for climate research.
• SRM 1721 represents a significant advancement in the metrology of atmospheric greenhouse gases.
• The low uncertainties achieved set a new benchmark for gas standard reference materials.