Jorgensen B B, Des Marais D J
NASA, Ames Research Center, Moffett Field, CA 94035, USA.
Limnol Oceanogr. 1990;35(6):1343-55. doi: 10.4319/lo.1990.35.6.1343.
Oxygen microelectrodes were used to analyze the distribution of the diffusive boundary layer (DBL) at the sediment-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.
利用氧微电极分析了沉积物 - 水界面处扩散边界层（DBL）的分布情况，以及其与表面地形和流速的关系。从盐池中采集的沉积物被一层微生物垫覆盖，该微生物垫具有高耗氧率和明确的表面结构。通过DBL的扩散构成了沉积物吸氧的重要速率限制。随着上覆水的流速从0.3增加到7.7 cm s-1（在微生物垫上方1 cm处测量），平均有效DBL厚度从0.59减小到0.16 mm。同时，吸氧速率从3.9增加到9.4 nmol cm-2 min-1。通过以0.1 mm的空间分辨率对沉积物 - 水界面和DBL上边界进行三维测绘，研究了表面粗糙度和地形对DBL厚度和分布的影响。DBL边界遵循特征尺寸大于1/2 DBL厚度的微生物垫结构，但相对于微生物垫，DBL的起伏较小。沉积物 - 水界面和DBL上边界的有效表面积分别比平面大31%和14%。因此，相对于根据垂直氧微梯度计算的一维扩散通量，表面地形使通过沉积物 - 水界面的氧通量增加了49%。
