Nobuyuki Aoki

O 2 :CO 2 exchange ratios observed in a cool temperate deciduous forest ecosystem of central Japan

Detailed observations of O2:CO2 exchange ratios were conducted in a cool temperate deciduous forest located in central Japan. The exchange ratios of soil respiration and net assimilation were found to be 1.11±0.01 and 1.02±0.03 from soil chamber and branch bag measurements, respectively. Continuous measurements of the atmospheric O2/N2 ratio and the CO2 concentration, made inside the canopy during a summer season, indicated that the average exchange ratio was lower in the daytime (0.87±0.02) than in the nighttime (1.03±0.02) with a daily mean value of 0.94±0.01. The observed average daytime and nighttime exchange ratios were nearly consistent with the corresponding values obtained from a one-box canopy O2/CO2 budget model simulation of net turbulent O2 and CO2 fluxes between the atmosphere and the forest ecosystem. Our results suggest that the daily mean exchange ratios of the net turbulent O2 and CO2 fluxes depend sensitively on the forest ecosystem processes.

Final report on international comparison CCQM-K68: Nitrous oxide in synthetic air

Nitrous oxide (N2O) is one of six greenhouse gases that are regulated by the Kyoto Protocol and has a Global Warming Potential (GWP) that is 296 times that of carbon dioxide. Global levels of nitrous oxide have increased at a rate of 0.25%/yr (0.8 ppb/yr) during the last ten years. In order to monitor levels of nitrous oxide in the atmosphere, it is necessary to use measurement standards with demonstrated equivalence at the highest level of accuracy. This report describes the results of a key comparison of standard gas mixtures of nitrous oxide in synthetic air at an amount fraction of 320 nmol/mol. This key comparison is part of the programme of the Gas Analysis Working Group (GAWG) of the CCQM to demonstrate the equivalence of the standards and measurement capabilities of the NMIs for greenhouse gases. It will support the development of measurement capability at the NMIs for nitrous oxide with uncertainties within the target set by the Global Atmospheric Watch (GAW) programme of the WMO for its global monitoring networks. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Development of an Analytical System Based on a Magneto-pneumatic Oxygen Analyzer for Atmospheric Oxygen Determination

A high-precision analytical system to observe the variations in the amount fractions of atmospheric oxygen with a very small uncertainty was developed. The system comprises a magneto-pneumatic oxygen analyzer and three automatic pressure controllers. The drift of the analyzers signal intensity can be reduced when the amount fractions of oxygen in the sample and reference gases are similar because the temperature coefficient of the analyzer linearly depends on the difference between these amount fractions. The repeatability of oxygen determination and the long-term stability of the system were tested to assess the applicability of the analyzer to field-based measurements for continuous atmospheric observations. The standard deviation of the average for 10-min measurements in the 5-day long-term stability test was 0.7 μmol mol-1 after a temperature correction. This indicates that the system can continuously measure the amount fractions of oxygen in the atmosphere for a few days without interruption for any calibration and/or compensation for the signal drift.

Accurate determination of formaldehyde amount fraction in cylinders using mixtures of primary standards of formaldehyde in nitrogen prepared by a gravimetric permeation method

A reliable method for the quantification of formaldehyde (HCHO) amount fractions is required, because the results of comparisons between individual techniques used for the quantification of HCHO amount fractions often disagree owing to unknown causes. One reliable method comprises the quantification of HCHO using working gas standards in which the HCHO amount fraction is linked to the International System of Units (SI). In this work, the SI traceability of HCHO amount fractions in mixtures of commercial HCHO in nitrogen in cylinders used as working gas standards was established by calibrating them against primary gas standard mixtures (mixtures of HCHO in N2), which were prepared by a permeation method and were traceable to SI. The expanded relative uncertainties (k = 2) of the amount fractions in the primary gas standard mixtures were less than 0.6 %. The quantitative values of the amount fractions in the working gas standards had relative expanded uncertainties (k = 2) of 0.7 %–0.9 %.

Final report of international comparison APMP.QM-S2.2015 of oxygen in nitrogen at 0.2 mol/mol

1) National Metrology Institute of Japan, National Institute of Advanced Industry and Science Technology, Umezono 1-1-1, Tsukuba, Ibaraki, Japan 2) Center for Measurement Standards, Industrial Technology Research Institute, Kuang Fu Rd, Hsinchu, 30011, Taiwan 3) National Institute of Metrology Thailand, 3⁄4-5 Moo 3, Klong 5, Klong Luang, Pathumthani 12120, Thailand 4) Chemicals Evaluation and Research Institute, Japan, 1600 Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama, Japan 5) Karaganda branch of RSE, Kazakhstan Institute of Metrology, Angerskaya st., 22/2, 100009, Kazakhstan