Using a gamma-ray spectrometer for soil moisture monitoring: development of the the gamma Soil Moisture Sensor (gSMS)

A new type of soil moisture sensor has been developed that uses gamma-rays emitted by the soil to determine the soil moisture content. Natural radionuclides emit radiation that is detected by this gamma Soil Moisture Sensor (gSMS). Gamma-rays are attenuated by moisture in the soil and therefore the flux of gamma photons could act as a proxy for the amount of moisture present in the soil. Preliminary results show that the total gamma flux seen by the sensor is also influenced by variations in atmospheric radon concentrations. Therefore, the total gamma count cannot be used as a proxy for soil moisture and spectral analysis is needed to filter out the radon-induced noise and correlate the
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K and
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Th concentration with the soil moisture content. Static measurements have been initiated to determine the accuracy needed for establishing the soil moisture content variation over time.