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Olivine Dissolution in Seawater: Implications forCO 2 Sequestration through Enhanced Weathering in CoastalEnvironments

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ABSTRACT

Enhanced weathering of (ultra)basic silicate rocks such as olivine-richdunite has been proposed as a large-scale climate engineering approach.When implemented in coastal environments, olivine weathering is expectedto increase seawater alkalinity, thus resulting in additional CO2 uptake from the atmosphere. However, the mechanisms of marineolivine weathering and its effect on seawater–carbonate chemistryremain poorly understood. Here, we present results from batch reactionexperiments, in which forsteritic olivine was subjected to rotationalagitation in different seawater media for periods of days to months.Olivine dissolution caused a significant increase in alkalinity ofthe seawater with a consequent DIC increase due to CO2 invasion,thus confirming viability of the basic concept of enhanced silicateweathering. However, our experiments also identified several importantchallenges with respect to the detailed quantification of the CO2 sequestration efficiency under field conditions, which includenonstoichiometric dissolution, potential pore water saturation inthe seabed, and the potential occurrence of secondary reactions. Beforeenhanced weathering of olivine in coastal environments can be consideredan option for realizing negative CO2 emissions for climatemitigation purposes, these aspects need further experimental assessment.

No MeSH data available.


Temporal development of olivine dissolution response variablesin experiment A3. Symbols denote mean seawater-corrected values (seethe Materials and Methods section) for theolivine treatment (OLI), with error bars denoting standard error ofthe mean (SEM). Circles: values from filtered seawater treatment (FSW);triangles: values from artificial seawater treatment (ASW); squares:values from artificial seawater without calcium treatment (ASW-Ca);diamonds: values from artificial seawater without calcium and magnesiumtreatment (ASW-CaMg). The reported units are μmol/kg of seawater(corrected for control values), except for pH, which is in pH unitson the Total scale.
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fig2: Temporal development of olivine dissolution response variablesin experiment A3. Symbols denote mean seawater-corrected values (seethe Materials and Methods section) for theolivine treatment (OLI), with error bars denoting standard error ofthe mean (SEM). Circles: values from filtered seawater treatment (FSW);triangles: values from artificial seawater treatment (ASW); squares:values from artificial seawater without calcium treatment (ASW-Ca);diamonds: values from artificial seawater without calcium and magnesiumtreatment (ASW-CaMg). The reported units are μmol/kg of seawater(corrected for control values), except for pH, which is in pH unitson the Total scale.

Mentions: In experiment A3, large differences inthe release of dissolution products were observed between the differentseawater media. All four media displayed a quasi-linear ΔSiresponse with time (Figure 2). The ΔSi attained at the end of the experiment waslowest in the natural seawater (FSW: 68 μmol Si kg–1) and artificial seawater (ASW: 82 μmol Si kg–1) and increased markedly when Ca2+ and Mg2+ were replaced by Na+ in the medium (ASW-Ca: 122 μmolSi kg–1; ASW-CaMg: 162 μmol Si kg–1).


Olivine Dissolution in Seawater: Implications forCO 2 Sequestration through Enhanced Weathering in CoastalEnvironments
Temporal development of olivine dissolution response variablesin experiment A3. Symbols denote mean seawater-corrected values (seethe Materials and Methods section) for theolivine treatment (OLI), with error bars denoting standard error ofthe mean (SEM). Circles: values from filtered seawater treatment (FSW);triangles: values from artificial seawater treatment (ASW); squares:values from artificial seawater without calcium treatment (ASW-Ca);diamonds: values from artificial seawater without calcium and magnesiumtreatment (ASW-CaMg). The reported units are μmol/kg of seawater(corrected for control values), except for pH, which is in pH unitson the Total scale.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382570&req=5

fig2: Temporal development of olivine dissolution response variablesin experiment A3. Symbols denote mean seawater-corrected values (seethe Materials and Methods section) for theolivine treatment (OLI), with error bars denoting standard error ofthe mean (SEM). Circles: values from filtered seawater treatment (FSW);triangles: values from artificial seawater treatment (ASW); squares:values from artificial seawater without calcium treatment (ASW-Ca);diamonds: values from artificial seawater without calcium and magnesiumtreatment (ASW-CaMg). The reported units are μmol/kg of seawater(corrected for control values), except for pH, which is in pH unitson the Total scale.
Mentions: In experiment A3, large differences inthe release of dissolution products were observed between the differentseawater media. All four media displayed a quasi-linear ΔSiresponse with time (Figure 2). The ΔSi attained at the end of the experiment waslowest in the natural seawater (FSW: 68 μmol Si kg–1) and artificial seawater (ASW: 82 μmol Si kg–1) and increased markedly when Ca2+ and Mg2+ were replaced by Na+ in the medium (ASW-Ca: 122 μmolSi kg–1; ASW-CaMg: 162 μmol Si kg–1).

View Article: PubMed Central - PubMed

ABSTRACT

Enhanced weathering of (ultra)basic silicate rocks such as olivine-richdunite has been proposed as a large-scale climate engineering approach.When implemented in coastal environments, olivine weathering is expectedto increase seawater alkalinity, thus resulting in additional CO2 uptake from the atmosphere. However, the mechanisms of marineolivine weathering and its effect on seawater–carbonate chemistryremain poorly understood. Here, we present results from batch reactionexperiments, in which forsteritic olivine was subjected to rotationalagitation in different seawater media for periods of days to months.Olivine dissolution caused a significant increase in alkalinity ofthe seawater with a consequent DIC increase due to CO2 invasion,thus confirming viability of the basic concept of enhanced silicateweathering. However, our experiments also identified several importantchallenges with respect to the detailed quantification of the CO2 sequestration efficiency under field conditions, which includenonstoichiometric dissolution, potential pore water saturation inthe seabed, and the potential occurrence of secondary reactions. Beforeenhanced weathering of olivine in coastal environments can be consideredan option for realizing negative CO2 emissions for climatemitigation purposes, these aspects need further experimental assessment.

No MeSH data available.