Sediment acidification and temperature increase in an artificial CO2 vent

de Beer, Dirk; Lichtschlag, Anna ORCID:; Flohr, Anita ORCID:; van Erk, Marit Rianne; Ahmerkamp, Soeren; Holtappels, Moritz; Haeckel, Matthias; Strong, James. 2021 Sediment acidification and temperature increase in an artificial CO2 vent. International Journal of Greenhouse Gas Control, 105, 103244.

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We investigated the effect of an artificial CO2 vent (0.0015−0.037 mol s−1), simulating a leak from a reservoir for carbon capture and storage (CCS), on the sediment geochemistry. CO2 was injected 3 m deep into the seafloor at 120 m depth. With increasing mass flow an increasing number of vents were observed, distributed over an area of approximately 3 m. In situ profiling with microsensors for pH, T, O2 and ORP showed the geochemical effects are localized in a small area around the vents and highly variable. In measurements remote from the vent, the pH reached a value of 7.6 at a depth of 0.06 m. In a CO2 venting channel, pH reduced to below 5. Steep temperature profiles were indicative of a heat source inside the sediment. Elevated total alkalinity and Ca2+ levels showed calcite dissolution. Venting decreased sulfate reduction rates, but not aerobic respiration. A transport-reaction model confirmed that a large fraction of the injected CO2 is transported laterally into the sediment and that the reactions between CO2 and sediment generate enough heat to elevate the temperature significantly. A CO2 leak will have only local consequences for sediment biogeochemistry, and only a small fraction of the escaped CO2 will reach the sediment surface.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 17505836
Date made live: 26 Jan 2021 15:38 +0 (UTC)

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