The effect of redox conditions and bioirrigation on nitrogen isotope fractionation in marine sediments
The effect of redox conditions and bioirrigation on nitrogen isotope fractionation in marine sediments
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DOI：
10.1016/j.gca.2016.04.040
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发表时间：
2016-07
影响因子：
5
通讯作者：
J. Rooze;C. Meile
中科院分区：
文献类型：
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作者：
J. Rooze;C. Meile
固定氮源和汇的氮同位素特征可用于限制海洋氮收支。然而，报告的底栖N2生产过程中的分馏差异很大。要评估的范围和机制负责这样的观察，我们进行了一个模型研究，以评估在何种程度上硝化，反硝化，厌氧氨氧化有助于原位N2生产的同位素组成。考虑到不同的水动力制度，从生物灌溉扩散为主的运输。底栖生物的氧化还原条件被认为是控制氮同位素效应，这是在还原条件下的硝化和厌氧氨氧化过程中的分馏和氧化条件下的反硝化过程中的分馏。环境参数，如矿化率，生物灌溉强度，上覆水的化学成分影响底栖生物氧化还原分带，因此也底栖生物N同位素效应。计算了各种生物灌溉强度和矿化率下的底栖N2产生的N同位素效应，发现在常见条件下约为−3‰。这一数值类似于以前对全球底栖N2生产的氮同位素效应的估计，并进一步限制了水柱与底栖N2生产的相对重要性。
Nitrogen isotopic signatures of sources and sinks of fixed nitrogen (N) can be used to constrain marine nitrogen budgets. However, the reported fractionation during benthic N2production varies substantially. To assess the range and mechanisms responsible for such observations, we conducted a model study to evaluate the extent to which nitrification, denitrification, and anaerobic ammonium oxidation contribute to the isotopic composition of in situ N2production. Different hydrodynamic regimes were taken into account, ranging from bioirrigation to diffusion-dominated transport. The benthic redox conditions were found to control the N isotope effect, which under reducing conditions is driven by fractionation during nitrification and anaerobic ammonium oxidation and under oxidizing conditions by fractionation during denitrification. Environmental parameters, such as the mineralization rate, the bioirrigation intensity, and chemical composition of the overlying water affect the benthic redox zonation and therefore also the benthic N isotope effect. The N isotope effect of benthic N2production was computed for a wide range of bioirrigation intensities and mineralization rates, and found to be approximately −3‰ for commonly encountered conditions. This value is similar to previous estimates of the global N isotope effect of benthic N2production, and further constrains the relative importance of water column vs. benthic N2production.