Department of Automatics, Electrical Engineering and Electronic Technology, Technical University of Cartagena, 30202 Murcia, Spain.
Department Plants, Soils and Climate, Utah State University, Logan, UT 84322, USA.
Sensors (Basel). 2020 Nov 22;20(22):6678. doi: 10.3390/s20226678.
The number of sensors, ground-based and remote, exploiting the relationship between soil dielectric response and soil water content continues to grow. Empirical expressions for this relationship generally work well in coarse-textured soils but can break down for high-surface area and intricate materials such as clayey soils. Dielectric mixing models are helpful for exploring mechanisms and developing new understanding of the dielectric response in porous media that do not conform to a simple empirical approach, such as clayey soils. Here, we explore the dielectric response of clay minerals and clayey soils using the mixing model approach in the frequency domain. Our modeling focuses on the use of mixing models to explore geometrical effects. New spectroscopic data are presented for clay minerals (talc, kaolinite, illite and montmorillonite) and soils dominated by these clay minerals in the 1 MHz-6 GHz bandwidth. We also present a new typology for the way water is held in soils that we hope will act as a framework for furthering discussion on sensor design. We found that the frequency-domain response can be mostly accounted for by adjusting model structural parameters, which needs to be conducted to describe the Maxwell-Wagner (MW) relaxation effects. The work supports the importance of accounting for soil structural properties to understand and predict soil dielectric response and ultimately to find models that can describe the dielectric-water content relationship in fine-textured soils measured with sensors.
利用土壤介电响应与土壤含水量之间的关系，传感器的数量在不断增加，包括地面传感器和远程传感器。 这种关系的经验表达式在粗质地土壤中通常效果很好，但对于高表面积和复杂材料（如粘性土壤）可能会失效。 介电混合模型有助于探索机制，并对不符合简单经验方法的多孔介质中的介电响应（如粘性土壤）产生新的认识。 在这里，我们使用频域中的混合模型方法来研究粘土矿物和粘性土壤的介电响应。 我们的建模重点是使用混合模型来探索几何效应。 为粘土矿物（滑石、高岭石、伊利石和蒙脱石）以及以这些粘土矿物为主的土壤在 1 MHz-6 GHz 带宽内提供了新的光谱数据。 我们还提出了一种新的土壤水分保持方式分类法，希望这能成为进一步讨论传感器设计的框架。 我们发现，通过调整模型结构参数可以很好地解释频域响应，这需要进行调整以描述 Maxwell-Wagner (MW) 弛豫效应。 这项工作支持了考虑土壤结构特性的重要性，以了解和预测土壤介电响应，并最终找到可以描述用传感器测量的细质地土壤介电-含水量关系的模型。
