Oxygen Isotopic Ratio (O18/O16) of Carbon Dioxide at Comilla, Bangladesh

Yukio Terao
Earth System Division, National Institute for Environmental Studies (NIES)

2022/03/01

2012/06/29 - 2020/12/26

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

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English

From 2012/06/29 (ongoing)

23.43°N, 91.18°E

Elevation: 30 m
Sampling height: 8 m above ground

Flask samples were collected from June 2012 in Comilla, Bangladesh. Inlets were mounted at 8 m above ground level (on top of the 5 m tower on the roof of the one-storey weather station building) in CLA. Air samples were collected once a week (usually on Wednesdays) at 14:00 LT into a 1.5 L Pyrex flask with two stopcocks sealed with Viton O-rings via a sampling line. The sampling line contained a diaphragm pump and a freezer for dehumidification by a glass trap. The sampling flow rate was approximately 2 L min⁻¹, and the sample was passed through a −30 ℃ cooler and pressurized to 0.25 MPa after 10 min flushing through the sampling tube and flask. The sampled flasks were packed in a cardboard box and transported to the laboratory of the Center for Global Environmental Research (CGER), National Institute for Environmental Studies, Japan (NIES) (transportation period: 3–7 d), for analyses.
After the mole fraction analysis, we used the remaining air inside the flask for analysis of δ13C-CO₂ and δ18O-CO₂. The air was introduced into two traps sequentially (−100 and −197 ℃), which trapped H₂O and CO₂, respectively. Finally, CO₂ was sealed in a glass tube. Air δ13C-CO₂ and δ18O-CO2 were measured by MT-252 using the working standard CO₂ gas which was prepared in our laboratory.

The sample was injected into the analytical system 3 times per one sample, and the working standard gases were analyzed after every 6 samples. Values of δ13C-CO₂ and δ18O-CO₂ were reported against the VPDB scale using working standard gases which were calibrated with the NIES Atmospheric Reference CO₂ for Isotopic Studies (NARCIS).

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[2022/03/01]

Hitoshi Mukai
Center for Climate Change Adaptation, NIES

Yukio Terao
Earth System Division, NIES

Shohei Nomura^*1, Toshinobu Machida^*1, Motoki Sasakawa^*1, M. Kawser Ahmed^*2, Prabir K. Patra^*3
*1 Earth System Division, NIES
^*2 University of Dhaka
^*3 Research Institute for Global Change, JAMSTEC

Nomura, S., Naja, M., Ahmed, M., K., Mukai, H., Terao, Y., Machida, T., Sasakawa, M., and Patra, P. K. (2021). Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India and Comilla, Bangladesh. Atmos. Chem. Phys., 21, 16427–16452, 2021, doi:10.5194/acp-21-16427-2021.

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