Carbon isotope fractionation during calcium carbonate precipitation induced by urease-catalysed hydrolysis of urea | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Carbon isotope fractionation during calcium carbonate precipitation induced by urease-catalysed hydrolysis of urea

Type de publication:

Journal Article

Source:

Chemical Geology, Volume 330, p.39-50 (2012)

ISBN:

0009-2541

URL:

http://www.sciencedirect.com/science/article/pii/S0009254112003750

Mots-clés:

UMR 7154 ; Géochimie des isotopes stables ; Urease; Ureolysis; Calcium carbonate; Carbon isotopes; Isotopic fractionation factor

Résumé:

Stable carbon isotopic fractionation during calcium carbonate precipitation induced by urease‐catalysed hydrolysis of urea was experimentally investigated in artificial water at a constant temperature of 30 °C. Carbon isotope fractionation during urea hydrolysis follows a Rayleigh distillation trend characterized by a 13C‐enrichment factor of − 20 to − 22‰. CaCO3 precipitate is up to 17.9‰ 13C‐depleted relative to the urea substrate (− 48.9 ± 0.07‰). Initial CaCO3 precipitate forms close to isotopic equilibrium with dissolved inorganic carbon. Subsequent precipitation occurs at − 2 to − 3‰ offset from isotopic equilibrium, suggesting that the initial δ13C value of CaCO3 is reset through dissolution followed by reprecipitation with urease molecules playing a role in offsetting the δ13C value of CaCO3 from isotopic equilibrium. Potentially, this isotopic systematics may provide a tool for the diagnosis of ureolytically‐formed carbonate cements used as sealing agent. Moreover, it may serve as a basis to develop a carbon isotope tool for the quantification of ureolytically‐induced CO2 sequestration. Finally, it suggests carbon isotope disequilibrium as a hallmark of past enzymatic activity in ancient microbial carbonate formation.

Notes:

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