Intrinsic and model polymer hydrogel-induced soil structural stability of a silty sand soil as affected by soil moisture dynamics
Intrinsic and model polymer hydrogel-induced soil structural stability of a silty sand soil as affected by soil moisture dynamics
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DOI：
10.1016/j.still.2015.06.014
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发表时间：
2015-12-01
影响因子：
6.5
通讯作者：
Schaumann, G. E.
中科院分区：
文献类型：
--
作者：
Buchmann, C.;Bentz, J.;Schaumann, G. E.
水分动力学可以通过土壤颗粒的重新定向和有机结构的粘合来促进稳定土壤结构的形成。虽然土壤自然暴露于水分动力学，但如果土壤有机质（SOM）或粘土含量不足，结构稳定性相当低。虽然人们普遍认为水凝胶形成、可膨胀的有机物质可以增强结构稳定性，但由于缺乏适当的测试方法，其潜在机制尚未完全了解。我们研究的目的是了解土壤水分动态对掺入水凝胶膨胀特性的影响及其对土壤结构特性的影响。将一种物理不稳定的粉质砂土用聚丙烯酸（PAA）作为高度可膨胀的模型聚合物进行处理，并进行干燥/重冻循环或恒湿处理。在某些测量点，我们使用H-1核磁共振弛豫仪（H-1 NMR弛豫仪）研究了膨胀过程和水结合，以表征水凝胶和土壤孔隙中水的状态，并将这些信息与土壤样品的流变特性相结合。与未经处理的土壤相反，聚合物处理的土壤在屈服点表现出更高的变形（gamma）和更高的最大剪切应力（tau(max)），这是动态反应，但不是可逆的。H-1核磁共振弛豫仪测定的结构稳定性随着paa相关水的比例明显增加。这一关系表明，水凝胶的胀缩过程可以解释水凝胶诱导土壤结构稳定的滞后性和时间依赖性。总而言之，H-1核磁共振弛豫测量和流变学的结合将有助于研究土壤结构稳定性和som相关水依赖于环境动力学的发展机制。(C) 2015 Elsevier B.V.版权所有
Moisture dynamics can favour the formation of stable soil structure by reorientation of soil particles and their gluing by organic structures. While soils are naturally exposed to moisture dynamics, structural stabilization is rather low if the soil organic matter (SOM) or clay content is insufficient. Although it is accepted that hydrogel-forming, swellable organic substances can enhance structural stabilization, the underlying mechanisms are not yet fully understood due to the lack of appropriate testing methods. The objective of our study was to understand the impact of soil moisture dynamics on the swelling properties of an incorporated hydrogel and their implications for soil structural properties. A physically unstable, silty sand soil was treated with polyacrylic acid (PAA) as highly swellable model polymer and subjected either to drying/remoistening cycles or to constant moisture. At certain measurement points, we investigated swelling processes and water binding using H-1 nuclear magnetic resonance relaxometry (H-1 NMR relaxometry) in order to characterize the state of water entrapped in the hydrogel and soil pores and combined this information with rheological characteristics of the soil sample. Contrary to the untreated soil, the polymer-treated soil revealed both higher deformation (gamma) at the yield point and higher maximum shear stress (tau(max)), which reacted dynamically, but not reversibly on moisture dynamics and water redistribution. Structural stability clearly increased with the proportion of PAA-associated water assessed by H-1 NMR relaxometry. This relation suggests that swelling-shrinking processes in the hydrogel could explain the hysteretic and time-dependent nature of hydrogel-induced soil structural stabilization. All in all, the combination of H-1 NMR relaxometry and rheology will help to investigate mechanisms governing the development of soil structural stability and SOM-associated water in dependence of environmental dynamics. (C) 2015 Elsevier B.V. All rights reserved.