Effect of mucilage on water properties in the rhizosphere monitored by 1 H-NMR relaxometry
Effect of mucilage on water properties in the rhizosphere monitored by 1 H-NMR relaxometry
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DOI：
10.1016/j.micromeso.2017.07.044
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发表时间：
2017-07
影响因子：
5.2
通讯作者：
M. Brax;C. Buchmann;G. Schaumann
中科院分区：
文献类型：
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作者：
M. Brax;C. Buchmann;G. Schaumann
根尖产生的粘液是一种土生生物水凝胶，其骨架是一个三维的多糖聚合物网络，其水分含量可达90%以上。粘液的特殊生物水凝胶特性，如体积膨胀和收缩，会影响土壤的力学和水力特性。尽管如此，控制粘液和多孔土壤系统之间相互作用的物理化学机制仍然大多不清楚。据我们所知，目前还没有一种方法允许区分多孔土壤系统中的生物水凝胶相和孔隙水。在这项工作中，我们使用1H核磁共振弛豫法来分析土壤中生物水凝胶的存在和性质。土壤中的粘液导致了一种层次化的孔隙结构，由被土壤颗粒表面包围的聚合物生物水凝胶网络组成。与不含粘液的土壤相比，包裹在含粘液土壤中的水分子表现出加速的体松弛和更高的表面松弛系数。在模型土壤中，我们量化了凝胶效应，在这里定义为粘液对质子松弛的影响。对于含粘液和不含粘液的土壤，横向松弛速率和纵向松弛速率之间的差值被绘制为模型土壤颗粒倒数直径的函数。因此，凝胶效应的特征是加速的整体松弛和加速的表面松弛，分别被含有粘液的土壤的y截距增加和线性系数增加所削弱。
Mucilage produced at the root tips is a soil-born biohydrogel, whose framework is a three-dimensional polysaccharidic polymer network, which can contain over 90% water. The specific biohydrogel properties of mucilage, such as volumetric expansion and shrinkage, affect soil mechanical and hydraulic properties. Still, the physico-chemical mechanisms governing the interactions between mucilage and the porous soil system remain mostly unclear. To our best knowledge, no currently applied method allows the distinction between biohydrogel phases and pore water in the porous soil system.In this work, we used1H NMR relaxometry to analyze the presence and properties of biohydrogels in soil. Mucilage in soil leads to a hierarchical pore structure, consisting of the polymeric biohydrogel network surrounded by the surface of soil particles. Water molecules entrapped in mucilage-containing soils revealed an accelerated bulk relaxation and a higher surface relaxivity in comparison with soils not containing mucilage. In model soils, we quantified the gel effect, here defined as the influence of mucilage on proton relaxation. The difference between transversal and longitudinal relaxation rates was plotted as a function of the reciprocal diameter of the model soil particles for soils containing and not containing mucilage. The gel effect was thereby characterized by anaccelerated bulk relaxationand anaccelerated surface relaxation, traduced respectively by an increased y-intercept and an increased linear coefficient for mucilage-containing soil.