CLUMPED ISOTOPIC EQUILIBRIUM AND THE RATE OF ISOTOPE EXCHANGE BETWEEN CO2 AND WATER
CLUMPED ISOTOPIC EQUILIBRIUM AND THE RATE OF ISOTOPE EXCHANGE BETWEEN CO2 AND WATER
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DOI：
10.2475/04.2013.02
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发表时间：
2013-04-01
影响因子：
2.9
通讯作者：
Affek, Hagit P.
中科院分区：
文献类型：
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作者：
Affek, Hagit P.
CO2水合/脱水反应通过与水交换氧同位素来控制碳酸盐矿物和大气CO2中的氧同位素组成。使用δ O-18作为环境指标通常假设同位素平衡，即CO2和水之间的完全氧同位素交换。成团同位素是一种新的同位素示踪剂，用于CaCO 3和大气CO2中，并反映了两种重同位素C-13和O-18在这种情况下（以Delta（47）表示）的热力学偏好，以在低温下“聚集”在一起形成一个化学键。因此，使用Delta（47）作为温度的指示器依赖于同位素平衡的假设。这里介绍的实验检查与水相互作用的CO2的Delta（47）接近平衡值的速率。该速率在Delta（47）和Delta O-18之间是不可区分的，这表明与水的同位素交换也导致CO2同位素体之间的同位素重组，从而控制Delta（47）值。δ（47）和δ O-18之间的时间联系的直接含义是，当一个同位素系统显示不平衡时，无论是在DIC中还是在气相CO2中，另一个也会显示不平衡。由于CO2聚集同位素值与参与反应的水的氧同位素组成无关，因此Delta（47）中的不平衡往往比Delta O-18更容易确定。因此，聚集同位素和氧同位素的组合可能阐明δ O-18中疑似不平衡的情况（反之亦然）。
The reaction of CO2 hydration/dehydration controls the oxygen isotopic composition in both carbonate minerals and atmospheric CO2 through the exchange of oxygen isotopes with water. The use of delta O-18 as an environmental indicator typically assumes isotopic equilibrium, namely full oxygen isotope exchange between CO2 and water. Clumped isotopes is a new isotopic tracer that is used in both CaCO3 and atmospheric CO2 and reflects the thermodynamic preference of two heavy isotopes, C-13 and O-18 in this case (given as Delta(47)), to "clump" together into one chemical bond at low temperatures. As such, the use of Delta(47) as an indicator for temperature relies on the assumption of isotopic equilibrium. The experiments presented here examine the rate in which Delta(47) of CO2 that interact with water approaches the equilibrium values. This rate is indistinguishable between Delta(47) and delta O-18, suggesting that the isotope exchange with water also leads to reorganization of the isotopes among CO2 isotopologues thus controlling the Delta(47) values. The direct implication of the temporal link between Delta(47) and delta O-18 is that when one isotopic system shows disequilibrium, either in DIC or in gas phase CO2, so will the other. As CO2 clumped isotope values are independent of the oxygen isotopic composition of the water participating in the reaction, disequilibrium in Delta(47) is often identified more readily than in delta O-18. The combination of clumped isotopes and oxygen isotopes is therefore likely to elucidate cases of suspected disequilibrium also in delta O-18 (and vice versa).