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Cited by 81Marine and coastal ecosystemsCO2 Sequestration and Geologic InteractionsClimate Change and Geoengineering

Seawater carbonate chemistry considerations for ocean alkalinity enhancement research: theory, measurements, and calculations

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Schulz, Kai G., Bach, Lennart T., Dickson, Andrew G.·2023·State of the Planet
DOI 10.5194/sp-2-oae2023-2-2023

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Abstract

Abstract. Ocean alkalinity enhancement (OAE) is a proposed marine carbon dioxide removal (mCDR) approach that has the potential for large-scale uptake of significant amounts of atmospheric carbon dioxide (CO2). Removing anthropogenic legacy CO2 will be required to stabilise global surface temperatures below the 1.5–2 ∘C Paris Agreement target of 2015. In this chapter we describe the impacts of various OAE feedstocks on seawater carbonate chemistry, as well as pitfalls that need to be avoided during sampling, storage, and measurement of the four main carbonate chemistry parameters, i.e. dissolved inorganic carbon (DIC), total alkalinity (TA), pH, and CO2 fugacity (fCO2). Finally, we also discuss considerations in regard to calculating carbonate chemistry speciation from two measured parameters. Key findings are that (1) theoretical CO2 uptake potential (global mean of 0.84 mol of CO2 per mole of TA added) based on carbonate chemistry calculations is probably secondary in determining the oceanic region in which OAE would be best; (2) carbonate chemistry sampling is recommended to involve gentle pressure filtration to remove calcium carbonate (CaCO3) that might have been precipitated upon TA increase as it would otherwise interfere with a number of analyses; (3) samples for DIC and TA can be stabilised to avoid the risk of secondary CaCO3 precipitation during sample storage; and (4) some OAE feedstocks require additional adjustments to carbonate chemistry speciation calculations using available programs and routines, for instance if seawater magnesium or calcium concentrations are modified.

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  • Between 0.77-0.96 mol of CO2 may be taken up per mol of alkalinity added to seawater; this range is largely driven by temperature, and the global average is approximately 0.84.

    “Considering carbonate system thermodynamics, between 0.77-0.96 mol of CO2 may be taken up per mol of alkalinity added to seawater; this range is largely driven by temperature, and the global average is approximately 0.84. 3”

    From A framework for understanding efficiency losses of Ocean Alkalinity Enhancement (2026) · cites this paper as [3]

    Section 1.3 defines the CO₂ uptake factor as the molar increase in dissolved inorganic carbon per unit of alkalinity added after air–sea equilibration. It gives a range of 0.77–0.96 and says sea-surface temperature is the main determinant, but it does not give a global average of approximately 0.84. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Carbonate system thermodynamics provide a stoichiometric upper bound on the amount of CO2 that can be taken up per unit of alkalinity added.

    “Carbonate system thermodynamics provide a stoichiometric upper bound on the amount of CO2 that can be taken up per unit of alkalinity added”

    From A framework for understanding efficiency losses of Ocean Alkalinity Enhancement (2026) · cites this paper as [3]

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Research works printed but not linked: 30

  1. Bach, L. T.: The additionality problem of Ocean Alka- linity Enhancement, Biogeosciences Discuss. [preprint], https://doi.org/10.5194/bg-2023-122, in review, 2023. · DOI
  2. Bach, L. T., Gill, S. J., Rickaby, R. E. M., Gore, S., and Renforth, P.: CO 2 removal with enhanced weathering and ocean alkalinity enhancement: Potential risks and co- benefits for marine pelagic ecosystems, Front. Clim., 1, 7, https://doi.org/10.3389/fclim.2019.00007, 2019. · DOI · Paper page
  3. Dickson, A. G., Wesolowski, D. J., Palmer, D. A., and Mesmer, R. E.: Dissociation constant of bisulfate ion in aqueous sodium chloride solutions to 250 • C, J. Phys. Chem., 94, 7978-7985, https://doi.org/10.1021/j100383a042, 1990. · DOI
  4. Dickson, A. G., Sabine, C. L., and Christian, J. R.: Guide to best practices for ocean CO 2 measurements, PICES Spe- cial Publication 3, IOCCP Report 8, North Pacific Marine Science Organization, Sidney, British Columbia, 191 pp., https://doi.org/10.25607/OBP-1342, 2007. · DOI
  5. Douglas, N. K. and Byrne, R. H.: Achieving accu- rate spectrophotometric pH measurements using un- purified meta-cresol purple, Mar. Chem., 190, 66-72, https://doi.org/10.1016/j.marchem.2017.02.004, 2017. · DOI
  6. Eisaman, M. D., Geilert, S., Renforth, P., Bastianini, L., Campbell, J., Dale, A. W., Foteinis, S., Grasse, P., Hawrot, O., Löscher, C. R., Rau, G. H., and Rønning, J.: Assessing the technical aspects of ocean-alkalinity-enhancement approaches, in: Guide to Best Practices in Ocean Alkalinity Enhancement Research, edited by: Oschlies, A., Stevenson, A., Bach, L. T., Fennel, K., Rickaby, R. E. M., Satterfield, T., Webb, R., and Gat- tuso, J.-P., Copernicus Publications, State Planet, 2-oae2023, 3, https://doi.org/10.5194/sp-2-oae2023-3-2023, 2023. · DOI
  7. Fennel, K., Long, M. C., Algar, C., Carter, B., Keller, D., Laurent, A., Mattern, J. P., Musgrave, R., Oschlies, A., Ostiguy, J., Palter, J. B., and Whitt, D. B.: Modelling considerations for research on ocean alkalinity enhancement (OAE), in: Guide to Best Practices in Ocean Alkalinity Enhancement Research, edited by: Oschlies, A., Stevenson, A., Bach, L. T., Fennel, K., Rickaby, R. E. M., Satterfield, T., Webb, R., and Gattuso, J.-P., Copernicus Publi- cations, State Planet, 2-oae2023, 9, https://doi.org/10.5194/sp-2- oae2023-9-2023, 2023. · DOI · Paper page
  8. Flipkens, G., Fuhr, M., Fiers, G., Meysman, F. J. R., Town, R. M., and Blust, R.: Enhanced olivine dissolution in seawater through continuous grain collisions, Geochim. Cosmochim. Ac., 359, 84-99, https://doi.org/10.1016/j.gca.2023.09.002, 2023. · DOI
  9. Fuhr, K., Geilert, S., Schmidt, M., Liebetrau, V., Vogt, C., Led- wig, B., and Wallmann, K.: Kinetics of olivine weathering in seawater: An experimental study, Front. Clim., 4, 831587, https://doi.org/10.3389/fclim.2022.831587, 2022. · DOI
  10. He, J. and Tyka, M. D.: Limits and CO 2 equilibration of near-coast alkalinity enhancement, Biogeosciences, 20, 27-43, https://doi.org/10.5194/bg-20-27-2023, 2023. · DOI
  11. Ho, D. T., Bopp, L., Palter, J. B., Long, M. C., Boyd, P. W., Neuker- mans, G., and Bach, L. T.: Monitoring, reporting, and verification for ocean alkalinity enhancement, in: Guide to Best Practices in Ocean Alkalinity Enhancement Research, edited by: Oschlies, A., Stevenson, A., Bach, L. T., Fennel, K., Rickaby, R. E. M., Satterfield, T., Webb, R., and Gattuso, J.-P., Copernicus Publica- tions, State Planet, 2-oae2023, 12, https://doi.org/10.5194/sp-2- oae2023-12-2023, 2023. · DOI
  12. Humphreys, M. P., Daniels, C. J., Wolf-Gladrow, D. A., Tyrell, T., and Achterberg, E. P.: On the influence of marine biogeochemical processes over CO 2 exchange be- tween the atmosphere and ocean, Mar. Chem., 199, 1-11, https://doi.org/10.1016/j.marchem.2017.12.006, 2018. · DOI
  13. Lauvset, S. K., Key, R. M., Olsen, A., van Heuven, S., Velo, A., Lin, X., Schirnick, C., Kozyr, A., Tanhua, T., Hoppema, M., Jutterström, S., Steinfeldt, R., Jeansson, E., Ishii, M., Perez, F. F., Suzuki, T., and Watelet, S.: A new global interior ocean mapped climatology: the 1 • × 1 • GLODAP version 2, Earth Syst. Sci. Data, 8, 325-340, https://doi.org/10.5194/essd-8-325- 2016, 2016. · DOI
  14. Marion, G. M., Millero, F. J., and Feistel, R.: Precipitation of solid phase calcium carbonates and their effect on applica- tion of seawater S A -T -P models, Ocean Sci., 5, 285-291, https://doi.org/10.5194/os-5-285-2009, 2009. · DOI · Paper page
  15. Montserrat, F., Renforth, P., Hartmann, J., Leermakers, M., Knops, P., and Meysman, F. J. R.: Olivine Dissolution in Seawater: Im- plications for CO 2 Sequestration through Enhanced Weathering in Coastal Environments, Environ. Sci. Technol., 51, 3960-3972, https://doi.org/10.1021/acs.est.6b05942, 2017. · DOI
  16. Moras, C. A., Bach, L. T., Cyronak, T., Joannes-Boyau, R., and Schulz, K. G.: Ocean alkalinity enhancement -avoiding runaway CaCO 3 precipitation during quick and hydrated lime dissolution, Biogeosciences, 19, 3537-3557, https://doi.org/10.5194/bg-19- 3537-2022, 2022. · DOI
  17. Moras, C., Bach, L., Cyronak, T., Joannes-Boyau, R., and Schulz, K.: Effects of grain size and seawater salinity on brucite dissolu- tion and secondary calcium carbonate precipitation kinetics: im- plications for Ocean Alkalinity Enhancement, EGU General As- sembly 2023, Vienna, Austria, 24-28 April 2023, EGU23-330, https://doi.org/10.5194/egusphere-egu23-330, 2023a. · DOI
  18. Moras, C. A., Bach, L. T., Cyronak, T., Joannes-Boyau, R., and Schulz, K. G.: Preparation and quality control of in-house ref- erence materials for marine dissolved inorganic carbon and total alkalinity measurements, Limnol. Oceanogr. Methods, https://doi.org/10.1002/lom3.10570, online first, 2023b. · DOI
  19. Orr, J. C., Epitalon, J.-M., and Gattuso, J.-P.: Comparison of ten packages that compute ocean carbonate chemistry, Biogeo- sciences, 12, 1483-1510, https://doi.org/10.5194/bg-12-1483- 2015, 2015. · DOI · Paper page
  20. Pan, Y., Li, Y., Ma, Q., He, H., Wang, S., Cai, W.-J., Dong, B. Di, Y., Fu, W., and Chen, C.-T. A.: The role of Mg 2+ in inhibiting CaCO 3 precipitation from seawater, Mar. Chem., 237, 104036, https://doi.org/10.1016/j.marchem.2021.104036, 2021. · DOI
  21. Rau, G. H., Carroll, S. A., Bourcier, W. L., Singleton, M. J., Smith, M. M., and Aines, R. D.: Direct electrolytic dissolution of silicate minerals for air CO 2 mitigation and carbon-negative H 2 production, P. Natl. Acad. Sci. USA, 110, 10095-10100, https://doi.org/10.1073/pnas.1222358110, 2013. · DOI
  22. Schulz, K. G. and Maher, D. T.: Atmospheric Carbon Dioxide and Changing Ocean Chemistry, in: Marine Pollution -Monitoring, Management and Mitigation, edited by: Reichelt-Brushett, A., Springer, https://doi.org/10.1007/978-3-031-10127-4, 2023. · DOI
  23. Schulz, K. G., Bach, L. T., Bellerby, R. G. J., Bermúdez, R., Bü- denbender, J., Boxhammer, T., Czerny, J., Engel, A., Ludwig, A., Meyerhöfer, M., Larsen, A., Paul, A. J., Sswat, M., and Riebesell, U.: Phytoplankton blooms at increasing levels of atmospheric carbon dioxide: Experimental evidence for negative effects on prymnesiophytes and positive on small picoeukaryotes, Fron- tiers, Mar. Sci., 4, 64, https://doi.org/10.3389/fmars.2017.00064, 2017. · DOI
  24. Subhas, A. V., Marx, L., Reynolds, S., Flohr, A., Mawji, E. W., Brown, P. J., and Cael, B. B.: Microbial ecosys- tem responses to alkalinity enhancement in the North Atlantic Subtropical Gyre, Front. Clim., 4, 784997, https://doi.org/10.3389/fclim.2022.784997, 2022. · DOI
  25. Sulpis, O., Lauvset, S. K., and Hagens, M.: Current estimates of K 1 * K 2 * appear inconsistent with measured CO 2 system parameters in cold oceanic regions, Ocean Sci., 16, 847-862, https://doi.org/10.5194/os-16-847-2020, 2020. · DOI
  26. Takeshita, Y., Warren, J. K., Liu, X., Spaulding, R. S., Byrne, R. H., Carter, B. R., DeGrandpre, M. D., Murata, A., and Watanabe, S.: Consistency and stability of purified meta-cresol purple for spec- trophotometric pH measurements in seawater, Mar. Chem., 236, 104018, https://doi.org/10.1016/j.marchem.2021.104018, 2021. · DOI
  27. Turner, D. R., Achterberg, E. P., Chen, C.-T. A., Clegg, S. L., Hatje, V., Maldonado, M. T., Snader, S. G., van den Berg, C. M. G., and Wells, M.: Toward a Quality-Controlled and Accessible Pitzer Model for Seawater and Related Systems, Front. Mar. Sci., 3, 139, https://doi.org/10.3389/fmars.2016.00139, 2016. · DOI
  28. Tyka, M. D., Van Arsdale, C., and Platt, J. C.: CO 2 capture by pumping surface acidity to the depp ocean, Energy Environ. Sci., 15, 786-798, https://doi.org/10.1039/D1EE01532J, 2022. · DOI
  29. Uppström, L. R.: The boron/chlorinity ratio of deep-sea water from the Pacific Ocean, Deep-Sea Res. Oceanogr. Abstracts, 21, 161- 162, https://doi.org/10.1016/0011-7471(74)90074-6, 1974. · DOI
  30. Zeebe, R. and Wolf-Gladrow, D.: CO 2 in Seawater: Equilib- rium, Kinetics, Isotopes, Elsevier Science B.V., Amsterdam, the Netherlands, 360 pp., ISBN 0444509461, 2001.

Cited by

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Authors
Schulz, K. G., Bach, L. T., & Dickson, A. G.
Affiliations
  • Southern Cross University (AU)
  • University of Tasmania (AU)
  • Scripps Institution of Oceanography (US)
Corresponding author
Schulz, Kai G.
ORCID
Venue
State of the Planet
Publisher
Copernicus GmbH
Published
2023-11-27
Volume
2-oae2023
Pages
1-14
ISSN
2752-0706 (ISSN-L)
DOI
10.5194/sp-2-oae2023-2-2023
OpenAlex
W4389055956
Cited by
81
References
1
Citations by year
2026: 17 · 2025: 18 · 2024: 30 · 2023: 16
FWCI
10.89
Type
journal article
Language
en
Open access
Licence
Locations
  • State of the Planet (publishedVersion, cc-by)
  • Helmholtz Centre for Ocean Research Kiel (GEOMAR) (acceptedVersion, other-oa)
  • Informationszentrum Lebenswissenschaften (ZB MED) (submittedVersion, cc-by)
Funders
  • ClimateWorks Foundation (22-0296)
  • Prince Albert II of Monaco Foundation (n/a)
  • Australian Research Council (FT200100846)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal ecosystems
  • Physical Sciences › Environmental Science › Environmental Engineering › CO2 Sequestration and Geologic Interactions
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate Change and Geoengineering
Keywords
ocean alkalinity enhancement, marine carbon dioxide removal, seawater carbonate chemistry, dissolved inorganic carbon, total alkalinity, pH, fugacity of CO2, carbonate speciation, calcium carbonate precipitation

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