[A-OS26] 全球・海盆規模海洋観測システムの現状、研究成果と今後

[AOS26-04] BGC-Argo に搭載可能な自動連続炭酸系計測システムの開発

*茅根 創¹、山本 将史^2,1、藤田 乃里¹、佐藤 縁²、朝海 敏昭²、粥川 洋平²、辺見 彰秀⁴、栗原 晴子³、Dickson Andrew⁵ (1.東京大学、2.産業技術総合研究所、3.琉球大学、4.メビウスアドバンストテクノロジー、5.スクリップス海洋研究所)

キーワード：アルゴフロート、海洋酸性化、アルカリ度

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.