EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Atmospheric observations of CO2, 14CO2 and O2 concentrations to capture fossil fuel CO2 emissions from the Greater Tokyo Area

Yukio Terao1, Yasunori Tohjima1, Shigeyuki Ishidoya2, Mai Ouchi1, Yumi Osonoi1, Hitoshi Mukai1, Toshinobu Machida1, Hirofumi Sugawara3, Naoki Kaneyasu2, and Yosuke Niwa1
Yukio Terao et al.
  • 1Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan (
  • 2National Institute of Advanced Industrial Science and Technology, Japan
  • 3Department of Earth and Ocean Science, National Defense Academy, Japan

The Grater Tokyo Area is the most populated (38 million) metropolitan area in the world. To capture fossil fuel carbon dioxide (CO2) emissions from the Grater Tokyo Area, we performed ground-based atmospheric observations for measuring concentrations of CO2, radiocarbon in CO(14CO2), oxygen (O2) and carbon monoxide (CO) at Tokyo Skytree (TST, with high altitude (250m) inlet) and Yoyogi (YYG, turbulentCOflux measurement site located in resident area) in Tokyo and at National Institute for Environmental Studies (NIES, suburb/rural area) in Ibaraki, Japan. The 14COmeasurement was used for separating the fossil fuel COemissions from the biotic emissions. Results from 14COmeasurements showed that a ratio of fossil fuel-derived COto the variation of COconcentrations was 71% in average for winter both at TST and YYG but varied from 44% to 92%, indicating significant contribution of biotic COin Tokyo. The O2:COexchange ratio (oxidation ratio, OR) was used for the partitioning of COinto emissions from gas fuels and gasoline. We observed larger OR in winter than in summer (due to both wintertime increases of fossil fuel combustion and summertime terrestrial biospheric activities) at TST and YYG and larger OR in the morning and late evening in winter due to increase of gas fuel combustion at YYG. We showed that the Oconcentrations might be also used as a proxy for continuous monitoring of fossil fuel COcontent by assuming typical ratio of gas fuels and gasoline combustions. The presenter will introduce the related projects including development of building/road-scale dynamic COmapping and grid-based COemission inventory with high special resolution in Tokyo.

How to cite: Terao, Y., Tohjima, Y., Ishidoya, S., Ouchi, M., Osonoi, Y., Mukai, H., Machida, T., Sugawara, H., Kaneyasu, N., and Niwa, Y.: Atmospheric observations of CO2, 14CO2 and O2 concentrations to capture fossil fuel CO2 emissions from the Greater Tokyo Area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12366,, 2020


Display file