Sensitivity of Capacitance Soil Moisture Sensors to Nitrate Ions in Soil Solution
Sensitivity of Capacitance Soil Moisture Sensors to Nitrate Ions in Soil Solution
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DOI：
10.2136/sssaj2010.0074
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发表时间：
2010-11-01
影响因子：
2.9
通讯作者：
Birrell, S.
中科院分区：
文献类型：
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作者：
Chighladze, G.;Kaleita, A.;Birrell, S.
电容式传感器已被广泛应用于监测土壤水分和盐分，但对其对土壤溶液中特定离子的响应知之甚少。本实验室研究的目的是研究ECH(2)O EC-5和EC-10两种电容探针对土壤溶液中NO(3)浓度的敏感性，以及了解传感器对溶液中其他离子存在的响应的差异。将均质壤土浸湿到5个体积含水率(VWC)，用9种含有不同浓度的NO(3)(-)、Cl(-)或两者兼有的溶液制备了45个均匀堆积的土壤样品。对归一化数据的两阶段分析表明，离子类型和浓度仅对工作在5 MHz频率下的EC-10探针的响应有显著影响(P类似于0.01)。EC-5探头在70兆赫工作时的反应主要由VWC的变化来解释。适用于EC-10对单个溶液的响应的多个线性回归模型表明，当模型中包括温度时，浓度仅对被NO(3)溶液润湿的样品具有统计学意义的预测值。研究证实，在相对较低的频率(5 MHz)下工作的电容探头对NO(3)浓度的变化比在氯中更敏感。我们将这种效应归因于离子质量的不同，离子质量的不同表现为离子特定频率下电导率的增加。然而，还需要更多的实验工作来准确地定义测量介电测量中离子诱导效应的最佳频率，并量化它们之间的相互关系。
Capacitance type sensors have been widely used to monitor soil water content and salinity, but little is known about their response to specific ions in soil solution. The goal of this laboratory study was to investigate the sensitivity of two capacitance probes, ECH(2)O EC-5 and EC-10, to NO(3) concentration in soil solutions, as well as to understand the differences in sensor response to the presence of other ions in the solutions. Forty-five uniformly packed soil samples were prepared using a homogenized loam soil wetted to five volumetric water contents (VWC) with nine solutions containing different concentrations of NO(3)(-), Cl(-), or both. A two-stage analysis of the normalized data revealed that ion type and concentration had a significant effect (P similar to 0.01) only for the response of the EC-10 probes operating at a frequency of 5 MHz. The response of the EC-5 probes, operating at 70 MHz, was mainly explained by changes in VWC. Multiple linear regression models fitted to the EC-10 response to individual solutions showed that concentration had a statistically significant predictive value only for samples wetted with NO(3) solutions when temperature was incorporated in the model. The study confirmed that capacitance probes operating at a relatively low frequency of 5 MHz are more sensitive to changes in NO(3) concentration than in Cl. We attributed this effect to the difference in ion mass that manifests through an increase in conductivity at ion-specific frequency. Additional experimental work is needed, however, to accurately define optimal frequencies for measuring ion-induced effects on dielectric measurement and to quantify interrelations between them.