In this second part of this study, primary standard gas mixtures (PSMs) as used for calibrations for the greenhouse gases carbon dioxide and methane have been compared. The nominal amount-of-substance fraction levels were 365 µmol/mol for carbon dioxide and 1.8 µmol/mol for methane. The matrix was synthetic air, simulated by a mixture of nitrogen, oxygen (209 mmol/mol) and argon (9.3 mmol/mol). The measurements took place in the spring of 2003. In the protocol, it was foreseen to have the PSMs produced for this study in a small range, enabling regression analysis on the data to assess the consistency of the gas mixtures. The direct comparison of the PSMs shows agreement for carbon dioxide at 365 µmol/mol nominal within 0.52 µmol/mol (0.14% relative) standard uncertainty. One cylinder lies between the 95% and 99% boundaries of the regression line, and after removing this cylinder from the dataset the standard deviation of the x-residuals reduces to 0.18 µmol/mol (0.05% relative). This value for the standard deviation is substantially greater than the stated standard uncertainties for several cylinders. The standard deviation of the x-residuals for methane at 1.8 µmol/mol nominal is 0.011 µmol/mol. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM.

Monitoring the state of oceans and their evolution in space and time is of fundamental importance as they are severely impacted by climate change, showing an increase in temperature, acidity and stratification. The role of metrology in the marine sector is relevant for helping oceanographers consolidate measurement approaches already in place by introducing concepts like metrological traceability and measurement uncertainty. The aim of this paper is to present some examples of successful and potential applications of metrology in oceanographic research, with a focus on past and ongoing activities in the framework of joint research cooperation, which could be applied by oceanographers to consolidate the comparability of data acquired in different experimental conditions, and places and time for some essential ocean variables. Scientific cooperation in the framework of joint research projects is particularly useful for supporting measurement capabilities in marine research worldwide, and the technologies and methods developed so far represent a starting point for improvements in international monitoring networks. These techniques may be applied by laboratories and centres working in the marine sector. Applications and possible future developments will also be discussed in this paper.

Purity analysis of parent gases used to produce reference gas mixtures is fundamental to assure the metrological traceability of the certified gas composition, and the use of purity data in the calculation of the mixture composition should be performed in accordance with the requirements of international standards. Purity analysis can be difficult to realize since limited measurement standards are available for the determination of trace levels of gaseous compounds. The first step of purity analysis is the definition of the impurities considered critical or significant to the final composition of a mixture. In this work, we present the activity carried out for the identification and quantification of impurities of carbon dioxide and water in some ultrapure gases used for the preparation of primary certified reference gas mixtures of carbon dioxide at atmospheric amount fraction (400–800 µmol·mol⁻¹), by means of different spectroscopic techniques (Fourier Transform IR, Non-Dispersive IR and Cavity Ring-Down). Dynamic dilution was used for the generation of reference mixtures for the calibration of the analyzers by using calibrated Mass Flow Controllers. The certified reference gas mixtures produced with the tested pure gases will also be applied to characterization studies and calibration protocols for gas sensors used both for outdoor and indoor monitoring.