THE DIFFUSIVE BOUNDARY-LAYER OF SEDIMENTS - OXYGEN MICROGRADIENTS OVER A MICROBIAL MAT
THE DIFFUSIVE BOUNDARY-LAYER OF SEDIMENTS - OXYGEN MICROGRADIENTS OVER A MICROBIAL MAT
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DOI：
10.4319/lo.1990.35.6.1343
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发表时间：
1990-09-01
影响因子：
4.5
通讯作者：
MARAIS, DJD
中科院分区：
文献类型：
--
作者：
JORGENSEN, BB;MARAIS, DJD
采用氧微电极分析了沉积物-水界面扩散边界层（DBL）的分布与表面形貌和流速的关系。从盐水池中收集的沉积物被一层微生物席覆盖，该微生物席具有高耗氧率和明确的表面结构。通过DBL的扩散是沉积物吸氧速率的重要限制因素。随着上覆水流速从0.3 cm s-1增加到7.7 cm s-1（在垫面上方1 cm处测量），平均有效DBL厚度从0.59 mm减少到0.16 mm。同时，吸氧速率从3.9 nmol cm-2 min-1增加到9.4 nmol cm-2 min-1。通过0.1 mm空间分辨率的沉积物-水界面和DBL上部边界三维制图，研究了表面粗糙度和地形对DBL厚度和分布的影响。DBL边界遵循垫层结构，其特征尺寸为bbb1 /2 DBL厚度，但DBL相对于垫层有一个阻尼起伏。沉积物-水界面和DBL上部边界的有效表面积分别比平面大31%和14%。因此，相对于由垂直氧微梯度计算的一维扩散通量，表面地形使穿过沉积物-水界面的氧通量增加了49%。
Oxygen microelectrodes were used to analyze the distribution of the diffusive boundary layer (DBL) at the sedimen-water interface in relation to surface topography and flow velocity. The sediment, collected from saline ponds, was covered by a microbial mat that had high oxygen consumption rate and well-defined surface structure. Diffusion through the DBL constituted an important rate limitation to the oxygen uptake of the sediment. The mean effective DBL thickness decreased from 0.59 to 0.16 mm as the flow velocity of the overlying water was increased from 0.3 to 7.7 cm s-1 (measured 1 cm above the mat). The oxygen uptake rate concurrently increased from 3.9 to 9.4 nmol cm-2 min-1. The effects of surface roughness and topography on the thickness and distribution of the DBL were studied by three-dimensional mapping of the sediment-water interface and the upper DBL boundary at 0.1-mm spatial resolution. The DBL boundary followed mat structures that had characteristic dimensions > 1/2 DBL thickness but the DBL had a dampened relief relative to the mat. The effective surface area of the sediment-water interface and of the upper DBL boundary were 31 and 14% larger, respectively, than a flat plane. Surface topography thereby increased the oxygen flux across the sediment-water interface by 49% relative to a one-dimensional diffusion flux calculated from the vertical oxygen microgradients.