Direct measurement of diffusivity within diatom aggregates containing transparent exopolymer particles
Direct measurement of diffusivity within diatom aggregates containing transparent exopolymer particles
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DOI：
10.4319/lo.2007.52.1.0001
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发表时间：
2007-01
影响因子：
4.5
通讯作者：
H. Ploug;U. Passow
中科院分区：
文献类型：
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作者：
H. Ploug;U. Passow
我们提出了第一个直接测量的表观扩散率内硅藻聚集体使用扩散率微传感器。透明的外聚合物颗粒（TEP）和聚集体干质量（TEP和细胞）在相同的聚集体扩散率测量后确定。TEP中的碳占骨料干质量的8 - 12%。然而，聚集体中TEP的（湿）体积分数平均比细胞大7.2倍，并且随着聚集体尺寸的增加而降低，与细胞相似。交换性孔隙水含量占骨料体积的87 - 98%。聚集体内的气体的平均表观扩散系数在海水中的自由扩散系数的0.90和0.95倍之间。使用扩散反应模型，我们分析了海洋雪中的草酸浓度。海洋雪中的表观扩散系数为0.9倍，其在海水中的自由扩散系数，和一个特定的净二氧化硅溶解速率为0.002小时21可以解释的观察，即海洋雪中的柠檬酸浓度显着高于环境水。
We present the first direct measurements of apparent diffusivity within diatom aggregates using a diffusivity microsensor. Transparent exopolymer particles (TEP) and aggregate dry mass (TEP and cells) were determined in the same aggregates after diffusivity measurements. Carbon in TEP comprised 8‐12% of aggregate dry mass. The (wet) volume fraction of TEP in aggregates, however, was on average 7.2‐fold larger than that of cells, and it decreased with increasing aggregate size similar to that of cells. The exchangeable pore‐water content occupied 87‐98% of the aggregate volume. The average apparent diffusivities of gases within aggregates ranged between 0.90 and 0.95 times the free diffusion coefficient in seawater. Using a diffusion‐reaction model, we analyzed silicic acid concentrations within marine snow. An apparent diffusivity of silicic acid within marine snow being 0.9 times its free diffusion coefficient in seawater, and a specific net silica dissolution rate of 0.002 h21 could explain the observation that concentrations of silicic acid are significantly higher within marine snow compared to that of the ambient water.