[H-SC07] 地球温暖化防止と地学（CO2地中貯留・有効利用、地球工学）

[HSC07-12] Mechanisms inducing anomalously high pCO₂ without CO₂ leakage in coastal environment

*渡辺 雄二^1,2、内本 圭亮^1,2、西村 真^1,2、三戸 彩絵子^1,2、薛 自求^1,2 (1.二酸化炭素地中貯留技術研究組合、2.公益財団法人地球環境産業技術研究機構)

キーワード：海底下CO2貯留、海域監視、CO2漏出、二酸化炭素分圧、総アルカリ度

When CO₂ is stored in sub-seabed geological formations in Japan, marine monitoring is mandatory to detect CO₂ leakage as soon as possible should it occur. In the Tomakomai CCS Demonstration Project, a threshold line based on a negative correlation between partial pressure of CO₂ (pCO₂) and dissolved Oxygen saturation in seawater is used to detect an anomalously high value of pCO₂, which is suspected to be a sign of CO₂ leakage. Although CO₂ leakage has never occurred in Tomakomai, pCO₂ values obtained in the monitoring have frequently exceeded the threshold line; that is, many false-positives have been produced. It is important to consider what can be causes of the false-positives. To discuss the causes, we analyzed data observed in the marine monitoring of the Tomakomai project, and meteorological data at Tomakomai. It is implied that weather conditions, such as wind speeds and precipitation, were related with false-positives. Also, we found that total alkalinity was remarkably low at a monitoring survey where many false-positives were observed. The low values of total alkalinity make pCO₂ values higher than usual, and consequently they might produce many false-positives. Based on the results, we are going to present how to avoid or reduce false-positives.