Estimation of sand water content using GPR combined time-frequency analysis in the Ordos Basin, China

Abstract

Groundwater is the key factor of determining the growth of vegetation. Identifying the characteristics of groundwater is an important basis to formulate a management plan for water resources and develop the technology of controlling desertification in arid areas scientifically. It is also important to the environmental protection in China. Ground penetrating radar (GPR) signals produce a special response to the changes in water content during propagation, thus it is essential to study the propagation of electromagnetic pulse in aeolian sand with different water content. The GPR tests of aeolian sand samples with different water content were conducted by a GPR system, dielectric constant meter, and conductivity meter. The temporal and frequency spectral characteristics of electromagnetic signals measured from aeolian sand samples were analyzed. The results show that the dielectric constant and conductivity of aeolian sand increase nonlinearly as the water content increases, and the attenuation coefficient of electromagnetic pulses increases parabolically. Meanwhile, the temporal waveform fluctuates significantly at the boundary of different media, and its two-way travel time increases nonlinearly as the water content increases, the pulse velocity decreases nonlinearly. Furthermore, the peak frequency of the spectrum for a signal propagating through aeolian sand decreases as the water content increases. The peak frequency is concentrated in the 1000 to 1400 MHz range, but the shape and bandwidth of the spectrum are less affected by water content. The above-mentioned correlations can provide a water content estimation of aeolian sand with direct value to the local authorities which are involved in the decision-making process for effective water management in arid and semi-arid area.

A Thermoacoustic Imaging System for Noninvasive and Nondestructive Root Phenotyping

“…Microwave applicator arrays, especially with recent advances in silicon and GaN devices enabling the use of portable high-power microwave sources [17], can be used to efficiently beamform energy to desired depths in soil and spatially steer beams for targeted excitation. Moreover, spectroscopic approaches that measure the TA signals at different microwave frequencies can be used as a sensing knob to identify parameters of interest like soil clay composition [18] and soil water content [19].…”