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Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation

Journal of Crystal Growth

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DOI: 10.1016/j.jcrysgro.2011.12.069

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Abstract

Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10−4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10−4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation
Series title:
Journal of Crystal Growth
DOI:
10.1016/j.jcrysgro.2011.12.069
Volume
352
Issue:
1
Year Published:
2012
Language:
English
Publisher:
Elsevier
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
Branch of Regional Research-Central Region
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Crystal Growth
First page:
151
Last page:
154
Country:
United States