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A kinetic pressure effect on calcite dissolution in seawater.

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Title: A kinetic pressure effect on calcite dissolution in seawater.
Authors: Dong, Sijia1 sijiadon@usc.edu, Subhas, Adam V.2,3, Rollins, Nick E.1, Naviaux, John D.2, Adkins, Jess F.2, Berelson, William M.1
Source: Geochimica et Cosmochimica Acta. Oct2018, Vol. 238, p411-423. 13p.
Subjects: Calcite, Carbonate minerals, Rock-forming minerals, Seawater, Saline waters
Abstract: This study provides laboratory data of calcite dissolution rate as a function of seawater undersaturation state (1 −  Ω ) under variable pressure. 13 C-labeled calcite was dissolved in unlabeled seawater and the evolving δ 13 C composition of the fluid was monitored over time to evaluate the dissolution rate. Results show that dissolution rates are enhanced by a factor of 2–4 at 700 dbar compared to dissolution at the same Ω under ambient pressure (10 dbar). This dissolution rate enhancement under pressure applies over an Ω range of 0.65–1 between 10 dbar and 700 dbar. Above 700 dbar (up to 2500 dbar), dissolution rates become independent of pressure. The observed enhancement is well beyond the uncertainty associated with the thermodynamic properties of calcite under pressure (partial molar volume ΔV), and thus should be interpreted as a kinetic pressure effect on calcite dissolution. Dissolution at ambient pressure and higher pressures yield non-linear dissolution kinetics, the pressure effect does not significantly change the reaction order n in Rate = k(1 −   Ω ) n , which is shown to vary from 3.1 ± 0.3 to 3.8 ± 0.5 from 10 dbar to 700 dbar over Ω  = 0.65–0.9. Furthermore, two different dissolution mechanisms are indicated by a discontinuity in the rate-undersaturation relationship, and seen at both ambient and higher pressures. The discontinuity, Ω critical = 0.87 ± 0.05 and 0.90 ± 0.03 at 10 dbar and 1050 dbar respectively, are similar within error. The reaction order, n, at Ω  > 0.9 is 0.47 ± 0.27 and 0.46 ± 0.15 at 10 dbar and 700 dbar respectively. This Ω critical is considered to be the threshold between step retreat dissolution and defect-assisted dissolution. The kinetic enhancement of dissolution rates at higher pressures is related to a decrease in the interfacial energy barrier at dissolution sites. The impact of pressure on the calcite dissolution kinetics implies that sinking particles would dissolve at shallower depths than previously thought. [ABSTRACT FROM AUTHOR]
Copyright of Geochimica et Cosmochimica Acta is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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Header DbId: egs
DbLabel: Engineering Source
An: 131295192
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
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  Data: A kinetic pressure effect on calcite dissolution in seawater.
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  Data: <searchLink fieldCode="AR" term="%22Dong%2C+Sijia%22">Dong, Sijia</searchLink><relatesTo>1</relatesTo><i> sijiadon@usc.edu</i><br /><searchLink fieldCode="AR" term="%22Subhas%2C+Adam+V%2E%22">Subhas, Adam V.</searchLink><relatesTo>2,3</relatesTo><br /><searchLink fieldCode="AR" term="%22Rollins%2C+Nick+E%2E%22">Rollins, Nick E.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Naviaux%2C+John+D%2E%22">Naviaux, John D.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Adkins%2C+Jess+F%2E%22">Adkins, Jess F.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Berelson%2C+William+M%2E%22">Berelson, William M.</searchLink><relatesTo>1</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Geochimica+et+Cosmochimica+Acta%22">Geochimica et Cosmochimica Acta</searchLink>. Oct2018, Vol. 238, p411-423. 13p.
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  Data: <searchLink fieldCode="DE" term="%22Calcite%22">Calcite</searchLink><br /><searchLink fieldCode="DE" term="%22Carbonate+minerals%22">Carbonate minerals</searchLink><br /><searchLink fieldCode="DE" term="%22Rock-forming+minerals%22">Rock-forming minerals</searchLink><br /><searchLink fieldCode="DE" term="%22Seawater%22">Seawater</searchLink><br /><searchLink fieldCode="DE" term="%22Saline+waters%22">Saline waters</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: This study provides laboratory data of calcite dissolution rate as a function of seawater undersaturation state (1 −  Ω ) under variable pressure. 13 C-labeled calcite was dissolved in unlabeled seawater and the evolving δ 13 C composition of the fluid was monitored over time to evaluate the dissolution rate. Results show that dissolution rates are enhanced by a factor of 2–4 at 700 dbar compared to dissolution at the same Ω under ambient pressure (10 dbar). This dissolution rate enhancement under pressure applies over an Ω range of 0.65–1 between 10 dbar and 700 dbar. Above 700 dbar (up to 2500 dbar), dissolution rates become independent of pressure. The observed enhancement is well beyond the uncertainty associated with the thermodynamic properties of calcite under pressure (partial molar volume ΔV), and thus should be interpreted as a kinetic pressure effect on calcite dissolution. Dissolution at ambient pressure and higher pressures yield non-linear dissolution kinetics, the pressure effect does not significantly change the reaction order n in Rate = k(1 −   Ω ) n , which is shown to vary from 3.1 ± 0.3 to 3.8 ± 0.5 from 10 dbar to 700 dbar over Ω  = 0.65–0.9. Furthermore, two different dissolution mechanisms are indicated by a discontinuity in the rate-undersaturation relationship, and seen at both ambient and higher pressures. The discontinuity, Ω critical = 0.87 ± 0.05 and 0.90 ± 0.03 at 10 dbar and 1050 dbar respectively, are similar within error. The reaction order, n, at Ω  > 0.9 is 0.47 ± 0.27 and 0.46 ± 0.15 at 10 dbar and 700 dbar respectively. This Ω critical is considered to be the threshold between step retreat dissolution and defect-assisted dissolution. The kinetic enhancement of dissolution rates at higher pressures is related to a decrease in the interfacial energy barrier at dissolution sites. The impact of pressure on the calcite dissolution kinetics implies that sinking particles would dissolve at shallower depths than previously thought. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Geochimica et Cosmochimica Acta is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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      – Type: doi
        Value: 10.1016/j.gca.2018.07.015
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      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 13
        StartPage: 411
    Subjects:
      – SubjectFull: Calcite
        Type: general
      – SubjectFull: Carbonate minerals
        Type: general
      – SubjectFull: Rock-forming minerals
        Type: general
      – SubjectFull: Seawater
        Type: general
      – SubjectFull: Saline waters
        Type: general
    Titles:
      – TitleFull: A kinetic pressure effect on calcite dissolution in seawater.
        Type: main
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            NameFull: Dong, Sijia
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            NameFull: Subhas, Adam V.
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            NameFull: Rollins, Nick E.
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            NameFull: Naviaux, John D.
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            NameFull: Adkins, Jess F.
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            – D: 01
              M: 10
              Text: Oct2018
              Type: published
              Y: 2018
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              Value: 238
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