Development of a Northern Continental Air Standard Reference Material

Area of Science:

• Environmental Science
• Analytical Chemistry
• Atmospheric Science

Background:

• Greenhouse gas monitoring is critical for understanding climate change.
• Accurate standard reference materials are essential for reliable atmospheric measurements.
• The U.S. Congress mandated research support for climate change initiatives.

Purpose of the Study:

• To develop and certify primary standard mixtures (PSMs) of key greenhouse gases.
• To create a new Standard Reference Material (SRM) for northern hemisphere air.
• To support climate change research through precise gas mixture standards.

Main Methods:

• Gravimetric assignment of primary standard mixtures (PSMs).
• Charging of gas cylinders with northern hemisphere air at Niwot Ridge.
• Certification of ambient mole fractions of CO2, CH4, and N2O relative to PSMs.

Main Results:

• Developed PSMs of CO2, CH4, and N2O in a dry-natural air balance.
• Certified NIST SRM 1720 Northern Continental Air.
• Achieved relative expanded uncertainties <±0.06% for CO2/N2O and <0.2% for CH4.
• Demonstrated agreement within 0.05% (CO2), 0.13% (CH4), and 0.06% (N2O) between NIST and NOAA values.

Conclusions:

• NIST has produced highly accurate gaseous standard reference materials for greenhouse gases.
• This collaborative effort provides critical tools for climate change research and atmospheric monitoring.
• The new SRM 1720 offers the lowest uncertainties for a gaseous SRM from NIST to date.