Synthetic Zero Air Reference Material for High Accuracy Greenhouse Gas Measurements.

The purity analysis of zero air is a significant contributor to the uncertainty in preparing reference materials of high impact greenhouse gases, limiting progress toward coherent and comparable measurements required to assess climate trends. We have produced a commutable synthetic zero air reference material with an oxygen, nitrogen, and argon matrix closely matching atmospheric composition. This is the critical step in preventing systematic biases from pressure broadening effects when using these reference materials to calibrate instruments based on optical spectroscopy. The amount fractions of carbon dioxide, methane, and carbon monoxide, which are present as minor impurities in the zero air reference material, have been accurately quantified using a novel dilution device that can generate gas mixtures of these components at trace amount fractions. These developments will have a significant impact on advancing the state of the art in high accuracy reference materials and for baseline calibration of spectroscopic instrumentation.