Thermal Properties of Desert Soils Irrigated with Industrial and Municipal Wastewater.

The soil thermal properties are important to understand the coupled flow of heat and moisture in the vadose zone. Thermal conductivity (λ), thermal diffusivity (α), thermal resistivity (r), and volumetric specific heat (C), were measured using KD2 probe, Decagon Devices, Inc., for three different soils irrigated with tapwater and wastewater, separately.   Core and bulk soil samples were collected from areas irrigated with treated wastewater for different amounts of time: 0 year, 8 years and 14 years. Volumetric moisture content (θ) was measured using pressure plate apparatus at 0, -0.3, -1, -3,-5, -10, and -15 bars suctions. Good agreement was observed between modeled and measured λ values. Initial results showed significant difference for λ, r, α, and C at lower water potentials (-5, -10, and -15 bars) and non significant at saturation (0 bar) between soil treated with wastewater and normal tapwater. Lower λ, C, α, and higher r was observed in the soil treated with wastewater compared with the soil treated with normal tapwater. In addition, lower λ, C, α, and higher r was observed during 8 and 14 years of wastewater application than 0 year of wastewater application. Hence the quality of the irrigation water can play an important role in water and energy transport through soil.