Detection and quantification of a release of carbon dioxide gas at the seafloor using pH eddy covariance and measurements of plume advection

Koopmans, D; Meyer, V; Schaap, A; Dewar, M; Färber, P; Long, MC; Gros, J; Connelly, DP; Holtappels, M. 2021 Detection and quantification of a release of carbon dioxide gas at the seafloor using pH eddy covariance and measurements of plume advection. International Journal of Greenhouse Gas Control, 112. 103476. https://doi.org/10.1016/j.ijggc.2021.103476

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Official URL: http://dx.doi.org/10.1016/j.ijggc.2021.103476

Abstract/Summary

We detected a controlled release of CO2 (g) with pH eddy covariance. We quantified CO2 emission using mea�surements of water velocity and pH in the plume of aqueous CO2 generated by the bubble streams, and using model predictions of vertical CO2 dissolution and its dispersion downstream. CO2 (g) was injected 3 m below the floor of the North Sea at rates of 5.7–143 kg d − 1 . Instruments were 2.6 m from the center of the bubble streams. In the absence of injected CO2, pH eddy covariance quantified the proton flux due to naturally-occurring benthic organic matter mineralization (equivalent to a dissolved inorganic carbon flux of 7.6 ± 3.3 mmol m − 2 d − 1 , s.e., n = 33). At the lowest injection rate, the proton flux due to CO2 dissolution was 20-fold greater than this. To accurately quantify emission, the kinetics of the carbonate system had to be accounted for. At the peak injection rate, 73 ± 13% (s.d.) of the injected CO2 was emitted, but when kinetics were neglected, the calculated CO2 emission was one-fifth of this. Our results demonstrate that geochemical techniques can detect and quantify very small seafloor sources of CO2 and attribute them to natural or abiotic origins.

Item Type: Publication - Article
Additional Keywords: CO2 vent Offshore CCS Leakage detection and quantification Marine sediment Proton flux
Divisions: Plymouth Marine Laboratory > National Capability categories > Modelling
Plymouth Marine Laboratory > Science Areas > Marine Ecosystem Models and Predictions
Depositing User: S Hawkins
Date made live: 28 Oct 2021 10:17
Last Modified: 28 Oct 2021 10:17
URI: http://plymsea.ac.uk/id/eprint/9445

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