کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6436855 | 1637612 | 2013 | 7 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Li+ speciation and the use of 7Li/6Li isotope ratios for ancient climate monitoring Li+ speciation and the use of 7Li/6Li isotope ratios for ancient climate monitoring](/preview/png/6436855.png)
- The choice of solvent model is observed to severely influence conclusions.
- A tentative range of 1.00220 to 1.04448 is established for KOHâH2OL7/6i.
- We establish an effective isotopic fractionation Î7/6effLiCO32ââH2O containing speciation effects.
We have carried out a theoretical study of aqueous Li+ speciation including effects of ligand coordination, temperature and solution pH. We have calculated the isotope exchange equilibrium constant, KOHâH2O7/6Li, associated with the Li acid/base equilibrium and can constrain it to positive values. The consequences of this species dependent isotope fractionation are then studied using a model for Li-Carbonate coordination. We define an effective isotope fractionation, effÎ7/6LiCO32ââH2O, to model temperature and pH induced changes in Li isotope fractionation associated with the formation of Li-Carbonate species. We predict that, under normal oceanic conditions, effÎ7/6LiCO32ââH2O is not sensitive to pH indeed but may be significantly influenced (on the order of 12â°) by temperature. Since the isotope ratios found in Li containing calcium carbonate shells show no indications of variation in isotopic composition, we conclude that the mechanism by which Li is incorporated to this material is not dependent on aqueous Li speciation.
Journal: Chemical Geology - Volume 357, 24 October 2013, Pages 1-7