Dynamics and Stable Isotope Composition of Gaseous and Dissolved Oxygen
Dynamics and Stable Isotope Composition of Gaseous and Dissolved Oxygen
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气态氧和溶解氧的动力学和稳定同位素组成
DOI：
10.1111/j.1745-6584.2007.00328.x
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发表时间：
2007
期刊：
影响因子：
2.6
通讯作者：
M. Hendry
中科院分区：
文献类型：
--
作者：
L. Wassenaar;M. Hendry
包气带和地下水环境是大气O2的汇。氧气消耗的途径和速率主要与关键还原剂(例如，有机物、硫化物)的可用性和氧化速率有关，通过生物或非生物反应的组合。次表层O2的δ18O变化范围较大，包气带为+20‰~+39‰，地下水为+12‰~+46‰。包气带和含水层的耗氧总同位素分馏系数(αk)分别为0.970~1.300和0.980~1.030。这些数据表明，非饱和带和含水层中的δ18O模式可以归因于微生物介导的反应(αk=0.975-1.000)，但显然还有其他反同位素分馏过程(αk>；1.000)。间接证据表明，在硫化物氧化和铁-氢氧化物过程(或其他不明过程)的沉淀过程中处理的O2可能是18O显著耗尽的原因。总体而言，来自包气带和地下水的δ18O数据显示，在地下水和地下水环境中，通过消耗气体和溶解的O2进行同位素分馏比传统上仅归因于地质微生物呼吸的情况要复杂得多。考虑到这项研究产生的问题和令人费解的数据，有必要对地球地下和地下水中的氧气消耗过程进行进一步的详细研究。
The vadose zone and ground water environments are a sink for atmospheric O2. The pathways and rates of O2 consumption are primarily related to the availability and rate of oxidation of key reductants (e.g., organics, sulfides), through a combination of biological or abiotic reactions. The range in δ18O of O2 in the subsurface is large, from +20‰ to +39‰ (Vienna Standard Mean Ocean Water) in the vadose zone and from +12‰ to +46‰ in ground water. The aggregated O2 isotope fractionation by consumption (αk) was found to range from 0.970 to 1.300 and 0.980 to 1.030 in vadose zones and aquifers, respectively. These data suggest the δ18O patterns in both unsaturated zones and aquifers can be attributed to microbially mediated reactions (αk= range from 0.975 to 1.000), but there are apparently other inverse isotope fractionating processes (αk > 1.000). Circumstantial evidence suggested O2 processed during the sulfide oxidation and precipitation of Fe‐oxyhydroxides process (or other unidentified processes) could be the cause of the significant 18O depletions. Overall, δ18O data from vadose zones and ground water revealed that isotope fractionation by consumption of gaseous and dissolved O2 in the subsurface and ground water environments is more complicated than what has classically been attributed solely to geomicrobial respiration. Given the questions and inexplicable data arising from this study, further detailed research on O2 consuming processes in the Earth’s subsurface and ground water is warranted.