Calcite dissolution in sediments of the Ontong‐Java Plateau: In situ measurements of pore water O2 and pH
Calcite dissolution in sediments of the Ontong‐Java Plateau: In situ measurements of pore water O2 and pH
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DOI：
10.1029/96gb01522
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发表时间：
1996-09
影响因子：
5.2
通讯作者：
B. Hales;S. Emerson
中科院分区：
文献类型：
--
作者：
B. Hales;S. Emerson
我们提出了在现场电极测量沉积物电阻率，孔隙水氧，孔隙水pH值从三个站之间的2300和3000米的深度Ontong-Java高原在赤道西太平洋。其中一个站也是同时进行底栖生物箱孵化实验的地点[Jahnke等人，1994年]。孔隙水氧数据和稳态扩散和反应模型限制了沉积物中氧呼吸的深度依赖性速率，并意味着氧向沉积物的扩散通量为10-21 μmol cm−2 yr−1。鉴于这些呼吸速率，孔隙水pH值数据不能解释没有方解石溶解代谢产生的CO2。通过统计方法量化的解释观测结果所需的溶解量为3.5-6 μmol cm−2 yr−1，相当于这些沉积物中至少20-40%的方解石雨。超过65%的总溶解是由代谢CO2驱动的。受电极数据限制的氧通量和净方解石溶解与Jahnke等人[1994年]的底栖室测量结果一致。溶解通量虽然是这些沉积物中方解石早期成岩作用的重要组成部分，但低于早期溶解模型的预测值，Jahnke等人[1994年]可能无法用底栖室技术将其与零区分开来。在这项研究中发现的溶解速率低于以前的估计，因为呼吸反应集中在附近的沉积物-水界面，方解石溶解速率常数是非常小的。孔隙水pH值数据和模型的统计评估将方解石溶解速率常数限制在0.005-0.16% d−1，遵循原位技术而不是实验室方法确定的较低值的总体趋势。
We present in situ electrode measurements of sediment resistivity, pore water oxygen, and pore water pH from three stations between 2300 and 3000 m depth on the Ontong-Java Plateau in the western equatorial Pacific. One of these stations is also the site of a concurrent benthic chamber incubation experiment [Jahnke et al., 1994]. The pore water oxygen data and a steady state diffusion and reaction model constrain the depth-dependent rate of oxic respiration in the sediments and imply a diffusive flux of oxygen to the sediments of 10–21 μmol cm−2 yr−1. Given these respiration rates, the pore water pH data cannot be explained without calcite dissolution driven by metabolically produced CO2. The dissolution necessary to explain the observations, quantified by a statistical approach, is 3.5–6 μmol cm−2 yr−1, which corresponds to at least 20–40% of the calcite rain to these sediments. Over 65% of the total dissolution is driven by metabolic CO2. Oxygen fluxes and net calcite dissolution constrained by the electrode data are compatible with the benthic chamber measurements of Jahnke et al. [1994]. The dissolution flux, while a significant part of the early diagenesis of calcite in these sediments, is less than would be predicted by earlier models of dissolution, and Jahnke et al. [1994] probably could not distinguish it from zero with the benthic chamber technique. The dissolution rates found in this study are lower than previous estimates because the respiration reaction is concentrated near the sediment-water interface, and the calcite dissolution rate constants are very small. The statistical evaluation of the pore water pH data and model constrain the calcite dissolution rate constant to 0.005–0.16% d−1, following the general trend of lower values determined by in situ techniques rather than by laboratory methods.