Measurement of soil water diffusivity of an undisturbed forest soil using dual-energy gamma radiation technique

A procedure is described to measure the soil water diffusivity of a heterog eneous porous medium, a clay-loam forest soil,A dual-energy gamma-ray appar atus was used to determine nondestructively water content variations in soi l samples during infiltration. The general principles of the dual-source te chnique (in particular correction of the Compton effect caused by cesium ph otons in the americium window) are reviewed, and a calibration method to de termine the mass attenuation coefficients of soil is described. Infiltratio n measurements on disturbed soil samples were obtained by dual-energy gamma -ray technique to validate the calibration procedure. Imbibition tests were done on undisturbed soil core samples, and the soil water diffusivity of s oil was calculated with a classical Boltzmann method, An optimization techn ique was used to determine the parameters of the hydraulic diffusivity mode l.