O2/N2 ratios and CO2 mole fractions of air samples collected onbaord cargo ships sailing in the Pacific region

Yasunori Tohjima (orcid.org/0000-0003-2153-6376)
Earth System Division, National Institute for Environmental Studies (NIES)
https://researchmap.jp/read0003834?lang=en

2023/08/30

2001/11/01 - 2021/12/27

NIES
Email: cgerdb_admin(at)nies.go.jp

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Ver 1.0 (Last updated: 2023/08/30)

English

O₂/N₂ ratio, CO₂ mole fraction

5 per meg

From Nov. 01, 2001(ongoing)

55.96°N, 100.67°E, 55.96°N, 270.61°E, 37°S, 100.67°E, 37°S, 270.61°E

From an air intake placed on bow mast or at the the top of the bridge of the cargo ship, air is drawn in through a stainless tube to the cabine using a metal-bellows pump. After passing through a cold trap (−40℃) to reduce water vapor, the air samples are forced into Pyrex glass flasks equipped with two glass stopcocks sealed by Viton O-rings to a pressure of 0.2 MPa (0.1 MPa above the ambient pressure). The collected air samples are sent back to a laboratory in NIES, where O₂/N₂ ratio and CO₂ mole fractions are measured by a gas chromatograph equipped with a thermal conductivity detector (GC/TCD) and a non-dispersive infrared analyzer (NDIR), respectively.

The O₂/N₂ ratios of the air samples are reported as relative deviations from a reference gas according to δ(O₂/N₂)={(O₂/N₂)sample/(O₂/N₂)reference-1}x10⁶, which are express in per meg units. The reported δ(O₂/N₂) values and CO₂ mole fractions are determined against the NIES original O₂/N₂ scale and NIES 09 CO₂ scale.

[Free keywords]
[GCMD_Platform]
[GCMD_Science]

[2023/8/30]

Discrete flask sample

Toshinobu Machida
Earth System Division, National Institute for Environmental Studies (NIES)

Motoki Sasakawa
Earth System Division, National Institute for Environmental Studies (NIES)

Tohjima, Y. (2000), Method for measuring changes in the atmospheric O₂/N₂ ratio by a gas chromatograph equipped with a thermal conductivity detector, J. Geophys. Res., 105, 14,575–14,584, doi:10.1029/2000JD900057.

Y. Tohjima, H. Mukai, T. Machida, Y. Nojiri, M. Gloor (2005), First measurements of the latitudinal atmospheric O₂ and CO₂ distributions across the western Pacific, Geophys. Res. Lett., 32, L17805, doi:10.1029/2005GL023311.

Tohjima, Y., C. Minejima, H. Mukai, T. Machida, H. Yamagishi, and Y. Nojiri (2012), Analysis of seasonality and annual mean distribution of atmospheric potential oxygen (APO) in the Pacific region, Global Biogeochem. Cycles, 26, GB4008, doi:10.1029/2011GB004110.

Y. Tohjima, Y. Terao, H. Mukai, T. Machida, Y. Nojiri, and S. Makyutov (2015), ENSO-related variability in latitudinal distribution of annual mean atmospheric potential oxygen (APO) in the equatorial Western Pacific, Tellus-B, 67, 25869, doi:10.3402/tellusb.v67.25869.

Tohjima, Y., H. Mukai, T. Machida, Y. Hoshina, and S. Nakaoka (2019), Global carbon budgets estimated from atmospheric O₂/N₂ and CO₂ observations in the western Pacific region over a 15-year period, Atmos. Chem. Phys., 19, 9269-9285, doi:10.5194/acp-19-9269-2019.

Ministry of the Environment

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