JpGU-AGU Joint Meeting 2020

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[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS26] Global ocean observing systems, their recent status, research results and future directions

convener:Shigeki Hosoda(Japan Marine-Earth Science and Technology), Shuhei Masuda(Japan Agency for Marine-Earth Science and Technology), Yosuke Fujii(Meteorological Research Institute, Japan Meteorological Agency), Fujiki Tetsuichi(Japan Agency for Marine-Earth Science and Technology)

[AOS26-04] Development of autonomous continuous pH-alkalinity analyzer deployable to BGC-Argo float

*Hajime Kayanne1, Shoji Yamamoto2,1, Nori Fujita1, Yukari Sato2, Toshiaki Asakai2, Yohei Kayukawa2, Akihide Hemmi4, Haruko Kurihara3, Andrew Dickson5 (1.the University of Tokyo, 2.Agency of Industrial Science and Technology, 3.University of the Ryukyus, 4.Möbius Advanced Technology Ltd, 5.Scripps Institution of Oceanography)

Keywords:Argo float, Ocean Acidification, alkalinity

Measurement of two variables among measurable four (pH, CO2, total inorganic carbon and alkalinity) is necessary to determine the carbonate system in the ocean, fundamental to evaluate Ocean Acidification and carbon absorption capacity. A combination of pH-alkalinity provides most accurate result, however alkalinity has been measured by titration in laboratory for discrete samples. We have developed a flow-through analyzer to measure seawater pH and alkalinity. First, seawater sample is introduced to a flow channel by peristaltic pump, and its electric potential is measured by ISFET, then HCl is added and mixed with the sample within the flow line and its potential is measured by the other ISFET. They are calibrated by measurement of three different certificated reference materials (CRM) in the same line to obtain pH and alkalinity values with a repeatability of 0.002 and 1.5 µmol kg-1, respectively, equivalent to laboratory titration. The system was deployed on a shallow reef flat and measured pH-alkalinity continuously and autonomously. Based on the same conceptual design, and by minimizing the size by applying µ-TAS, we will develop an autonomous continuous pH-alkalinity analyzer deployable to BGC-Argo float. The power consumption and weight will be reduced to 1W and 1kg, respectively. The flow system and CRM/HCl will be packed in Hydrochlorofluorocarbon and seawater, respectively with their buoyancy sustained to the outside pressure. Pressure dependency of ISFET and the dissociation constants of carbonate system will also be investigated. Deployment of this system will reveal spatial and temporal change in the carbonate system in the ocean.