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首页> 外文期刊>Estuarine Coastal and Shelf Science >Delamination of smectite in river-borne suspensions at the fluvial/marine interface - An experimental study
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Delamination of smectite in river-borne suspensions at the fluvial/marine interface - An experimental study

机译：河流/海洋界面河流悬浮液中蒙脱石的分层-实验研究

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Fine fractions (<2 μm) from smectite-rich flood-plain sediments from the Elbe and Weser rivers in Germany were treated in the laboratory with synthetic sea salt solutions at different concentrations and for different periods of time to document sheet delamination of smectite particles at the fluvial/marine interface and thus simulate changes in clay minerals at the mouth of a river. The project consisted of two steps: (1) Pilot tests were made in 0.5% salt solutions (brackish environment) showing a nearly 2-min delay of the clearing of the clayey suspensions, when the suspension was redispersed 15 and 30 min later after the first measurement. This was due to an obviously increased number of fine laminae from disintegrated smectite particles. (2) X-ray diffraction studies (XRD) of the clayey material from suspensions in 0.0, 0.5,1.0, and 3.0% salt solutions after standing 10 min, and one and three weeks were made to document alteration reactions of smectite. An aliquot was pipetted periodically from each series, and oriented clay-mineral specimens were analyzed by XRD in air-dried, glycol- and glycerin-solvated states. The peak intensities in the XRD patterns of the clay minerals smectite, random-ordered mixed-layer illite/smectite (I—S), kaolinite, chlorite, and illite did not change in the salt-free series during the experiments. In contrast the peak intensities of smectite and I-S mineral in the air-dried and glycerin-solvated states after suspension in saline solutions decreased significantly. The d-values of the smectitic materials in the air-dried state also decreased after contact with the saline solutions, and in the glycerin-solvated state the full-width-at-half-maximum (FWHM) of the 001 smectite reflection increased by about 20%, indicating a reduction in grain size. The variations in FWHM, d-values and peak intensity of the smectitic material are assumed to be caused by an exchange of Na for Ca in the interlayer spaces and subsequent delamination of the particles along the Na-activated interlayers. Only those smectite particles in which adjacent sheets are still stabilized by the remaining Ca are preserved after contact with seawater. The experiments show that delamination of smectite and I—S mixed-layer minerals is likely to occur in the brackish environment at the mouth of a river. However, formation of these fine laminae is expected to be a transitional stage in the development of clay particle size, owing to the formation of floes and aggregates in the higher salt concentrations of seawater.
机译：来自德国易北河和威悉河的富含绿土的洪泛平原沉积物中的细小颗粒（<2μm）在实验室中用不同浓度和不同时间的合成海盐溶液处理，以记录在120℃下蒙脱石颗粒的薄片分层河流/海洋界面，从而模拟了河口粘土矿物的变化。该项目包括两个步骤：（1）在0.5％的盐溶液（微咸的环境）中进行的先导测试表明，在悬浮液在15分钟和30分钟后重新分散后，其悬浮液的清除几乎延迟了2分钟。第一次测量。这是由于分解的蒙脱石颗粒产生的细薄片的数量明显增加。 （2）静置10分钟后，用0.0％，0.5％，1.0％和3.0％盐溶液中的悬浮液对黏土材料进行X射线衍射研究（XRD），记录一，三周以记录绿土的蚀变反应。从每个系列中定期吸取等分试样，并通过风干，乙二醇和甘油溶剂化状态下的XRD分析定向的粘土矿物标本。在无盐系列中，粘土矿物蒙脱石，无序伊利石/蒙脱石（IS），高岭石，绿泥石和伊利石的XRD谱图的峰强度没有变化。相反，在盐溶液中悬浮后，在空气干燥和甘油溶剂化状态下，蒙脱石和I-S矿物的峰强度显着降低。与盐溶液接触后，在空气干燥状态下蒙皂石材料的d值也降低，在甘油溶剂化状态下，001蒙皂石反射的半峰全宽（FWHM）增加了约20％，表明晶粒尺寸减小。认为近晶缔合材料的FWHM，d值和峰强度的变化是由于在层间空间中Na与Ca的交换以及随后沿着Na活化的层间颗粒的分层而引起的。与海水接触后，仅保留其中相邻薄片仍被剩余Ca稳定的那些蒙脱石颗粒。实验表明，在河口咸淡的环境中，蒙脱石和IS混合层矿物很可能发生分层。然而，由于在较高盐浓度的海水中形成了絮凝物和聚集体，因此预计这些细薄片的形成将是粘土粒度发展的过渡阶段。

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