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DOI	10.1016/j.epsl.2021.116932
	The influence of hydrodynamics on the carbon isotope composition of inorganically precipitated calcite
	Yan H.; Dreybrodt W.; Bao H.; Peng Y.; Wei Y.; Ma S.; Mo B.; Sun H.; Liu Z.
发表日期	2021
ISSN	0012821X
卷号	565
英文摘要	It is often assumed that the carbon isotope composition (δ13C) of carbonate minerals records that of the dissolved inorganic carbon (DIC) species with insignificant disequilibrium effect. However, results from field observations and laboratory experiments have shown that the δ13C difference between calcite and solution can vary up to 3‰ even under a similar set of solution composition and temperature, raising uncertainties on the δ13C's paleoclimate and paleoecology implications. One likely cause is the variable calcite precipitation rates and pH values induced by different thicknesses of the stagnant liquid layer between solid and well mixed bulk solution (i.e., diffusion boundary layer, DBL). To test this hypothesis, we selected a well-studied natural travertine deposit (Baishuitai, SW China) which consists of meter-scale travertine terraces. Calcite crystals at both the pool bottom and the rim of the terraces are inorganically precipitated from solutions identical in chemical, isotopic composition and temperature, but different only in hydrodynamics. This difference results in thicker DBL for water at the pool-bottom than for water flowing across the rim. We found that the δ13C and Mg/Ca ratios are higher while Sr/Ca ratios are lower for the pool-bottom calcites than for the rim calcites. By applying a mass transfer model, we quantitatively link the differences in carbon isotope and elemental compositions of the abiogenic calcites to the different hydrodynamic conditions. The inverse variation in Mg/Ca and Sr/Ca ratios in calcites arises from the different precipitation rates between at the pool-bottom and at the rim, while the consistently lower δ13C for calcites at the rim is due to their higher pH at the solid-solution interface than for calcites precipitated at the pool-bottom. In contrast, calcite precipitation rate has little influence on carbon isotope fractionation between calcite and HCO−3. Our results demonstrate the role of DBL thickness in governing the δ13C of HCO−3 at mineral surface, which can assist to interpret the variable δ13C values of calcites in riverine or cave environments. © 2021 Elsevier B.V.
关键词	calcite carbon isotope fractionation diffusion boundary layer pH effect precipitation rate
英文关键词	Calcite; Carbon; Hydrodynamics; Isotopes; Lakes; Phase interfaces; Solid solutions; $+13$/C; Calcite precipitation; Carbon isotope composition; Carbon isotope fractionation; Carbon species; Diffusion boundary-layers; Dissolved inorganic carbon; Field observations; Precipitation rates; Sr/ca ratios; Boundary layers; calcite; carbon isotope; crystal structure; dissolved inorganic carbon; mineral property; paleoclimate; paleoecology; pH; precipitation (chemistry); travertine
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203347
作者单位	State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China; Faculty of Physics and Electrical Engineering, University of Bremen, Germany; International Center for Isotope Effects Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China; Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, United States; Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an, 710061, China
推荐引用方式 GB/T 7714	Yan H.,Dreybrodt W.,Bao H.,et al. The influence of hydrodynamics on the carbon isotope composition of inorganically precipitated calcite[J],2021,565.
APA	Yan H..,Dreybrodt W..,Bao H..,Peng Y..,Wei Y..,...&Liu Z..(2021).The influence of hydrodynamics on the carbon isotope composition of inorganically precipitated calcite.Earth and Planetary Science Letters,565.
MLA	Yan H.,et al."The influence of hydrodynamics on the carbon isotope composition of inorganically precipitated calcite".Earth and Planetary Science Letters 565(2021).