Oxygen isotope fractionation of dissolved oxygen during reduction by ferrous iron
Oxygen isotope fractionation of dissolved oxygen during reduction by ferrous iron
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DOI：
10.1016/j.gca.2008.10.012
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发表时间：
2009-01-01
影响因子：
5
通讯作者：
Poulson, Simon R.
中科院分区：
文献类型：
--
作者：
Oba, Yasuhiro;Poulson, Simon R.
为了更好地了解富二价铁地下水和酸性矿坑湖中氧的地球化学行为，在中性（pH 7）和酸性（pH 2）条件下，测量了FeSO4水溶液在10-54℃下无机还原过程中溶解氧气的氧同位素分馏因子，其中Fe（II）浓度最高可达0.67 mol L-1。氧还原速率随着温度的升高和Fe(II)浓度的增加而增加,中性条件下的准一级速率常数k为2.3~82.9 x 10(-6)S(-1),酸性条件下的准一级速率常数k为2.1~37.4 x 10(-7)S(-1)。中性和酸性条件下氧还原活化能分别为30.9±6.6 kJ mol(-1)和49.7±13.0 kJ mol-1。氧同位素富集因子（ε）随着温度的升高、二价铁浓度的增加以及酸性条件下反应速率的增加而变小，ε值范围为-4.5 ppm至-11.6 ppm。在中性条件下，ε 相对于温度或二价铁浓度不显示任何系统趋势，e 值范围为 -7.3 至 -10.3 千分之 与 Fe(II) 还原 O2 相关的氧同位素分馏因子的表征将适用于阐明地下水和酸性矿坑湖等环境中耗氧的过程，这些环境中可能发生了许多可能的过程（例如生物呼吸、还原物质的还原）。 (C) 2008 Elsevier Ltd. 保留所有权利。
The oxygen isotope fractionation factor of dissolved oxygen gas has been measured during inorganic reduction by aqueous FeSO4 at 10-54 degrees C under neutral (pH 7) and acidic (pH 2) conditions, with Fe(II) concentrations ranging up to 0.67 mol L-1, in order to better understand the geochemical behavior of oxygen in ferrous iron-rich groundwater and acidic mine pit lakes. The rate of oxygen reduction increased with increasing temperature and increasing Fe(II) concentration, with the pseudo-first-order rate constant k ranging from 2.3 to 82.9 x 10(-6)S(-1) under neutral conditions and 2.1 to 37.4 x 10(-7)S(-1) under acidic conditions. The activation energy of oxygen reduction was 30.9 +/- 6.6 kJ mol(-1) and 49.7 +/- 13.0 kJ mol-1 under neutral and acidic conditions, respectively. Oxygen isotope enrichment factors (epsilon) become smaller with increasing temperature, increasing ferrous iron concentration, and increasing reaction rate under acidic conditions, with epsilon values ranging from -4.5 parts per thousand to -11.6 parts per thousand. Under neutral conditions, epsilon does not show any systematic trends vs. temperature or ferrous iron concentration, with e values ranging from -7.3 to -10.3 parts per thousand Characterization of the oxygen isotope fractionation factor associated with 02 reduction by Fe(II) will have application to elucidating the process or processes responsible for oxygen consumption in environments such as groundwater and acidic mine pit lakes, where a number of possible processes (e.g. biological respiration, reduction by reduced species) may have taken place. (C) 2008 Elsevier Ltd. All rights reserved.