Trace metal mobility in sub-seabed sediments by CO2 seepage under high-pressure conditions

M Dolores Basallote; Ana R Borrero-Santiago; Carlos R Cánovas; Karen M Hammer; Anders J Olsen; Murat V Ardelan

doi:10.1016/j.scitotenv.2019.134761

Trace metal mobility in sub-seabed sediments by CO₂ seepage under high-pressure conditions

Sci Total Environ. 2020 Jan 15:700:134761. doi: 10.1016/j.scitotenv.2019.134761. Epub 2019 Oct 31.

Authors

M Dolores Basallote¹, Ana R Borrero-Santiago², Carlos R Cánovas³, Karen M Hammer⁴, Anders J Olsen⁵, Murat V Ardelan²

Affiliations

¹ Department of Chemistry, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway; Cátedra UNESCO/UNITWIN WiCop, Departamento de Química-Física, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Polígono Río San Pedro s/n, Puerto Real, Cádiz 11510, Spain. Electronic address: maria.basallote@dct.uhu.es.
² Department of Chemistry, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway.
³ Department of Earth Sciences & Research Center on Natural Resources, Health and the Environment (RENSMA), Faculty of Experimental Sciences, University of Huelva, Campus 'El Carmen' s/n, 21071 Huelva, Spain.
⁴ SINTEF Materials and Chemistry, Marine Environmental Technology, 7465 Trondheim, Norway.
⁵ Norwegian University of Science and Technology, Department of Biology, 7491 Trondheim, Norway.

PMID: 31706093
DOI: 10.1016/j.scitotenv.2019.134761

Abstract

Carbon capture and storage (CCS) is the third contributor to cumulative carbon emission reductions required by the second half of this century. Although this is a promising technology for reducing atmospheric CO₂, it is only affordable if the confinement of the gas is guaranteed for hundreds of years. Hence, it is of paramount importance to figure out and predict the chemical and biological effects associated with potential CO₂ leakage, to provide decision makers with a good basis for choosing technology and potential storage sites. To this end, a titanium reactor (1.4 m³) was used to study CO₂ seepage under realistic sub-seabed conditions (30 bar pressure and 7 °C). The injection of CO₂ was calibrated to decrease the pH value from 8.1 to 7.3, which may be the pH found near a leakage point. This pH value also coincides with predictions for near-future ocean pH under current CO₂ emissions worldwide. The results from this study demonstrate that there are some elements, i.e., Fe, Co, Pb, Ce, Zn and Cu, present in deep marine sediments, that are strongly affected by the reduced pH levels related to CO₂ addition. The dissolved concentrations of Fe, Pb and, to a lesser extent, Cr increased, due probably to weakening of the Fe/Mn shuttle by increased dissolved concentrations of CO₂. Desorption processes from oxyhydroxide surfaces due to acidification may explain the release of Co, Ni and Ce observed during the experiment. The increased CO₂ concentration also led to increased metal bioavailability, suggested by higher values for labile metal species. Conversely, Cd mobility seems not to be affected by CO₂-associated acidification. It is concluded that the determination of those elements most affected by CO₂-related acidification in a sub-seabed CO₂ storage perimeter (i.e., sediment, sediment-water interface and water column) would be a simple and effective technique to verify suspected leakage.

Keywords: Acidification; CO(2) leakage; Chemo-indicator; Sediment–water interface; Stable seafloor elements.