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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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  06 Jan 2021

06 Jan 2021

Review status: this preprint is currently under review for the journal AMT.

Inter-comparison of O2/N2 Ratio Scales Among AIST, NIES, TU, and SIO Based on Round-Robin Using Gravimetric Standard Mixtures

Nobuyuki Aoki1, Shigeyuki Ishidoya2, Yasunori Tohjima3, Shinji Morimoto4, Ralph F. Keeling5, Adam Cox5, Shuichiro Takebayashi4, and Shohei Murayama2 Nobuyuki Aoki et al.
  • 1National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba 305-8563, Japan
  • 2Research Institute for Environmental Management Technology (EMRI), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8569, Japan
  • 3Center for Environmental Measurement and Analysis, National Institute for Environmental Studies, Tsukuba 305-8506, Japan
  • 4Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
  • 5Scripps Institution of Oceanography, La Jolla, CA 92093-0244, USA

Abstract. A study was conducted to compare the δ(O2/N2) scales used by four laboratories engaged in atmospheric δ(O2/N2) measurements. These laboratories are the Research Institute for Environmental Management Technology, Advanced Industrial Science and Technology (EMRI/AIST), the National Institute for Environmental Studies (NIES), Tohoku University (TU), and Scripps Institution of Oceanography (SIO). Therefore, five high-precision standard mixtures for O2 molar fraction gravimetrically prepared by the National Metrology Institute of Japan (NMIJ), AIST (NMIJ/AIST) with a standard uncertainty of less than 5 per meg were used as round-robin standard mixtures. EMRI/AIST, NIES, TU, and SIO reported the analysed values of the standard mixtures on their own δ(O2/N2) scales, and the values were compared with the δ(O2/N2) values gravimetrically determined by NMIJ/AIST (the NMIJ/AIST scale). The δ(O2/N2) temporal drift in the five standard mixtures during the inter-comparison experiment was corrected based on the δ(O2/N2) values analysed before and after the experiments by EMRI/AIST. The scales are compared based on offsets in zero and span. The span offsets from the NMIJ/AIST scale ranged from −0.17 % to 3.3 %, corresponding with the difference of 0.29 Pg yr−1 in the estimates for land biospheric and oceanic CO2 uptakes. The zero offsets from the NMIJ/AIST scale are −581.0 ± 2.2, −221.4 ± 3.1, −243.0 ± 3.0, and −50.7 ± 2.4 per meg for EMRI/AIST, TU, NIES, and SIO, respectively. The atmospheric δ(O2/N2) values observed at Hateruma Island (HAT; 24.05° N, 123.81° E), Japan, by EMRI/AIST and NIES became comparable by converting their scales to the NMIJ/AIST scale.

Nobuyuki Aoki et al.

Status: open (until 03 Mar 2021)

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Nobuyuki Aoki et al.

Nobuyuki Aoki et al.


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