Errors of dual thermal probes due to soil heterogeneity across a plane interface

The dual thermal probe enables estimation of the thermal diffusivity, volum etric heat capacity (C), and thermal conductivity of soils. it has been muc h employed for moisture estimation because of the strong dependence of C on soil water content. The present study investigates the effectiveness of du al probes near heterogeneities. Exact solutions are found for four probe/so il configurations involving heterogeneity. In one configuration the heating probe is on the plane interface between different soils. For the three oth er configurations it is located close to three different discontinuities: n ear a soil surface and outside, and behind, a wetting front. Heterogeneity errors are found to be small provided the heterogeneity is no closer to the probes than probe separation (typically 0.006 m). Estimates of C may provi de good resolution of soil water content in critical regions such as near s urfaces and fronts.