土壤介电特性与其影响因素的相关性研究

Study on correlation among soil dielectric properties and its influencing factors

以北京市海淀区八家试验苗圃的黏壤土为研究对象,使用矢量网络分析仪NA7300A和平行板技术,探索40~150 MHz频率范围内,土壤体积含水率(6%~36%)、土壤尿素含量(0~1%)、土壤容重(1.2~2.6 g·cm-3)、温度(10~50℃)和含盐量(0~0.42%)对土壤介电特性的影响,并构建表征土壤介电特性的电抗估算模型。结果表明:土壤体积含水率在6%~30%范围内,不同测试频率下,电抗与含水率均具有良好的线性关系,电抗随含水率的增加而增大,当测试频率为100 MHz时,二者的线性度尤其好,决定系数(R2)大于0.97;尿素不会引起电抗值有规律的改变;随着土壤容重、含盐量增大以及温度升高,电抗增大。以电抗为因变量,含水率、容重、温度、含盐量、测试频率为自变量建立的多元线性回归模型的判定系数(R2)为0.92,概率P值小于显著性水平0.05,说明该模型可作为土壤介电特性估算模型,用于北京地区粘壤土的介电特性研究。

Clay loam in Haidian District,Beijing was selected as research object and the impacts of soil volume moisture content（ 6%-36%）,soil urea content（ 0-1%）,soil bulk density（ 1. 2-2. 6 g·cm-3）,temperature（ 10-50 ℃）,salt content（ 0-0. 42%） on soil dielectric properties were explored and analyzed by vector network analyzer NA7300 A based on parallel plate technology within the test frequency（ 40-150 MHz）,and estimation model of reactance with soil dielectric properties was built. It was shown that the reactance had good linear relation with soil moisture content at the range of 6%-30% under different test frequencies. The reactance value increased with the increase of moisture content. When the test frequency was 100 MHz,the determination coefficient（ R2） of the constructed linearity was higher than 0. 97. Urea did not cause the change of reactance value regularly. With the increase of bulk density,soil salinity and temperature,reactance value increased. The multiple linear regression model was established with reactance as the dependent variable and soil moisture content,bulk density,temperature,salt content and test frequency as independent variables,of which the determination coefficient（ R2） was 0. 92,andthe probability（ P） was less than the significance level of 0. 05. The results showed that the model could be used as estimation model to study the dielectric properties of clay loam in Beijing.