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Radioactivity

机译：放射性

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In this study, to better understand the factors controlling the concentration and isotope composition of lithium (Li) in the ocean, we investigated the behaviour of Li during interaction of kaolinite with artificial seawater. Dissolution of kaolinite in Li-free seawater at acidic conditions (exp. 1) results in a strong preferential release of light Li isotopes, with △~7Li_(aq-kaol)～-19‰, likely reflecting both the preferential breaking of ~6Li[sbnd]O bonds over ~7Li[sbnd]O bonds and the release of Li from the isotopically lighter AlO_6 octahedral sites. Sorption experiments on kaolinite (exp. 2) revealed a partition coefficient between kaolinite and fluid of up to 28, and an isotopic fractionation of -24‰. Thermodynamic calculation indicates authigenic smectites formed from the dissolution of kaolinite in seawater at pH 8.4 (exp. 3). The formation of authigenic phase strongly removed Li from the solution (with a partition coefficient between the solid and the fluid equal to 89) and led to an increase of ca. 25‰ in seawater δ~7 Li. This fractionation can be described by a Rayleigh fractionation model at the early stage of the experiment during rapid clay precipitation, followed, at longer reaction time, by equilibrium isotope fractionation during the much slower removal of aqueous Li via co-precipitation and adsorption. Both processes are consistent with a fractionation factor between the solid and the aqueous solution of ~-20‰. These experiments have implications for interpreting the Li isotopic composition of both continental and marine waters. For instance, the preferential release of ~6Li observed during kaolinite far-from-equilibrium dissolution could explain the transient enrichments in ~6Li observed in soil profiles. With regard to the evolution of seawater δ~7Li over geological time scales, our experimental results suggest that detrital material discharged by rivers to the ocean and ensuing "reverse chemical weathering" have the potential to strongly impact the isotopic signature of the ocean through the neoformation of clay minerals.
机译：在这项研究中，为了更好地了解控制海洋中锂（Li）浓度和同位素组成的因素，我们研究了Li期间高岭土与人工海水相互作用的行为。在酸性条件（Exp.1）的锂自由海水中Koolinite的溶解导致光Li同位素的强烈优先释放，具有χ〜7Li_（aq-kaol）〜-19〜，可能反映了〜6li的优先突破[SBND] O键合约〜7LI [SBND] O键，LI从同位素较轻ALO_6八面体位点粘合。高岭土的吸附试验（EXP.2）揭示了高达28的高岭石和流体之间的分区系数，以及-24‰的同位素分级。热力学计算表明由PH8.4（EXP.3）的海水中高岭石溶解形成的Aheatigenic蒙脱石。从溶液中形成Authigenic相的强烈地除去Li（固体之间的分配系数，并且流体等于89）并导致CA的增加。海水δ〜7李。该分馏可以在快速粘土沉淀期间通过实验早期的瑞利分馏模型描述，然后在较长的反应时间内，通过平衡同位素分馏在通过共沉淀和吸附的水溶液中的较慢除去。这两个方法都是一致的固体和〜-20°的水溶液之间的分馏因子。这些实验对解释大陆和海水的锂同位素组成有影响。例如，在高岭石远离平衡溶解期间观察到〜6LI的优先释放可以解释在土壤剖面中观察到的〜6LI中的瞬时富集。关于海水δ〜7Li的演变，我们的实验结果表明，河流向海洋排出的替代材料和随后的“逆向化学风化”有可能通过新邮件强烈影响海洋的同位素签名粘土矿物质。

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    《Oceanographic Literature Review》 |2020年第12期|2603-2603|共1页
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