Title: Long-Term ¹³C Uptake by ¹²C-Enriched Calcite

Abstract

Knowledge of the exchange of carbon isotopes between dissolved inorganic carbon and calcite minerals is of long-standing importance for the interpretation of sedimentary paleoclimate records and ¹⁴C transport in the geosphere. To assess the mechanism and rates of carbon isotope exchange, we equilibrated ¹²C-pure synthetic calcite particles in water, first in a glovebox and then in contact with atmospheric P_CO2 and ¹³C/¹²C ratio, at two different temperatures. Cavity ring-down infrared spectroscopy δ¹³C measurements of the solid revealed sustained 13C incorporation for over a period of 500 days (21 °C) and 125 days (50 °C). We developed a quantitative model for recrystallization and isotope exchange, assuming that the interfacial free energy provides a thermodynamic driving force for the growth of larger particles at the expense of smaller ones. Furthermore, this Ostwald ripening model did not reproduce the kinetics of 13C uptake and required greater coarsening than observed. Rather, the data were best explained by a mechanism involving surface exchange and solid-phase diffusion of 13C into the particles with an inferred effective diffusion constant at 21 °C of about 10^–25 m²/s. Although this work cannot rule out the possibility that structural or chemical aspects of the synthetic particles enabled faster ¹³C uptakemore » than could be observed in natural systems, this study adds to the body of the recent work, suggesting that fast exchange processes are possible, likely through grain boundaries and other defects.« less

Authors:

Géhin, Antoine ^[1]; Gilbert, Benjamin  ^[2];

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• Search DOE PAGES for ORCID "0000-0003-0853-0826"

Chakraborty, Sudipta  ^[3];

• Search DOE PAGES for author "Chakraborty, Sudipta"
• Search DOE PAGES for ORCID "0000-0003-3777-8302"

Stack, Andrew G.  ^[4];

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• Search DOE PAGES for ORCID "0000-0003-4355-3679"

Allard, Lawrence F.  ^[4];

• Search DOE PAGES for author "Allard, Lawrence F."
• Search DOE PAGES for ORCID "0000-0002-4552-8277"

Robinet, Jean-Charles ^[5]; Charlet, Laurent  ^[1]

• Search DOE PAGES for author "Charlet, Laurent"
• Search DOE PAGES for ORCID "0000-0003-3669-7316"

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+ Show Author Affiliations

1. Univ. Grenoble Alpes and CNRS (France)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. Univ. Grenoble Alpes and CNRS (France); Kanchrapara College, West Bengal (India)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
5. Agence Nationale pour la Gestion des Déchets Radioactifs (ANDRA), Chatenay-Malabry (France)

Publication Date:

Wed Apr 28 00:00:00 EDT 2021

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division

OSTI Identifier:

1832706

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

ACS Earth and Space Chemistry

Additional Journal Information:

Journal Volume: 5; Journal Issue: 5; Journal ID: ISSN 2472-3452

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; carbonate sediments; carbon isotope exchange; recrystallization; cavity ring-down spectroscopy; diffusion; carbon; calcite; inorganic carbon compounds; carbon isotopes