低频探地雷达地波法测定土壤含水量的可行性研究

利用地波法来探讨低频探地雷达(GPR)在土壤含水量测定方面的可行性。分别采用50 MHz和100 MHz天线的探地雷达地波法对黄淮海平原潮土地区砂壤土和砂土中的含水量进行了探测研究。结果表明,50 MHz天线GPR分辨率过低,在砂土和砂壤土中均无地波信号。100 MHz天线在砂壤土中无地波信号,但在砂土中可清晰读取出空气波和地波。TDR测得含水量为6.3%的砂土,用100 MHz天线地波法3次测定结果分别为5.9%,6.2%和6.5%,绝对误差均在0.4%以内。采用共中点法(CMP)和固定间距法(FO)相结合探测土壤含水量,在FO最佳天线间距1 m时测得灌水前后的砂土含水量分别为6.5%和20.2%,与TDR测定结果6.3%和19.7%相比,绝对误差在0.5%以内。100 MHz天线CMP和FO相结合的方法兼顾了CMP法读取地波的精确和FO法的快速便捷,在砂土的含水量测定应用中是可信、可行的。

Determining soil water content by using low-frequency ground-penetrating radar ground wave techniques

The feasibility of low-frequency ground-penetrating radar (GPR) in measuring soil water content by using ground wave technique was investigated in order to provide a new method for soil water content measurement in small-scale region. Water contents of sandy loam and sandy soils with GPR ground wave technique were measured in Huang-Huai-Hai Plain. Antenna separations of GPR were 50 MHz and 100 MHz respectively. The results showed that ground wave can neither be interpreted in sandy soil nor sandy loam with 50 MHz antenna and in sandy loam with 100 MHz antenna due to the strong attenuation of the GPR signal, but can be clearly read out in sandy soil with 100 MHz antenna. Sandy soil water content measured with 100 MHz antenna GPR ground wave techniques were 5.9%, 6.2% and 6.5% respectively for three replicates, while 6.3% with TDR measurement, absolute error was within 0.4%. Soil water content before and after irrigation were 6.5% and 20.2% respectively determined by CMP-FO (the combination of Common Mid-Point and Fixed Offset ) method and were 6.3% and 19.7% respectively by TDR, the absolute error was within 0.5%. CMP-FO method is accurate and time-saving, it is feasible and credible to determine soil water content in arid area with 100 MHz antenna GPR.