[A-OS25] [JJ] 地球温暖化・海洋酸性化に対する沿岸・近海域の海洋応答

[AOS25-P04] The dynamics of pore water in subsurface sediments at the site of controlled CO₂ release experiment

*Tsukasaki Ayumi¹、Hicks Natalie²、Taylor Peter²、鈴村 昌弘¹、Lichtschlag Anna³、Stahl Henrik⁴、James Rachael³ (1.産業技術総合研究所、2.スコットランド海洋科学協会、3.英国国際海洋センター、4.ザイード大学)

キーワード：二酸化炭素回収貯留、地球温暖化、堆積物、間隙水

Carbon capture and storage (CCS) in sub-seabed geological formations is a mitigation strategy that can aid the reduction of anthropogenic CO₂ emissions. In 2012, the QICS (Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage) project was undertaken by researchers from the UK and Japan. The project conducted a field-scale controlled CO₂ release experiment in order to examine the impacts on the marine ecosystem and evaluate the methods for detection and impact monitoring, should CO₂ leakage occur. Changes in the chemical composition of water and seabed sediment were detected, in particular, pH and dissolved inorganic carbon (DIC) of the sediment pore water during the CO₂ release. After the gas release was stopped, concentrations of all pore water constituents rapidly returned to pre-release values. The QICS team concluded that the environmental impacts from small-scale leakage is not ecologically significant.
We address two unsettled issues from QICS: (1) the mechanism behind the rapid recovery of pore water parameters to pre-release levels, and (2) the fate of the released CO₂ potentially remaining in the subsurface sediments. To settle these issues, we conducted field observation measurements at the QICS site, Ardmucknish Bay, in 2016, four years after the CO₂ release. Time series in situ monitoring of pore water chemistry in the subsurface sediments was conducted in order to investigate pore water dynamics. To characterize pore water behaviour more precisely, we conducted a tracer test using the custom-made pore water extractors. To trace the injected CO₂, carbonate content and stable carbon isotope ratio of the sediment and pore water were compared between the area close to the CO₂ release point and the unaffected reference site. In this presentation we focus on the pore water dynamics at the QICS site and show the results of field observation that influence benthic recovery from a CO₂ leak.