Thermal properties of an upper tidal flat sediment on the Texas Gulf Coast
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Increased land use change near fragile ecosystems can affect the ecosystem energy balance leading to increased global warming. One component of surface energy balance is soil storage heat flux. In past work, a complex thermal behavior was noticed in the shrink-swell sediment of the upper Nueces Delta (upper Rincon) during summer months as it dried. Soil storage heat flux was found to first increase, then decrease, as the soil dried. It was suggested that the complex behavior was due to the relationship between thermal diffusivity and soil moisture, where thermal diffusivity increases to a local maximum before decreasing with respect to decreasing soil moisture. This study explores the observed phenomenon in a controlled laboratory environment by relating the sediment shrinkage curve to changing heat transfer properties. Due to the complicated nature of the drying-shrinking sediment, it was necessary to measure the sediment shrinkage curve and heat transfer properties in separate experiments. The shrinkage curve was found by correlating measured sample volume with gravimetric moisture content. Heat transfer properties were found using a single needle heat pulse probe. A normalized gravimetric moisture content was used as a common variable to relate the shrinkage curve and heat transfer data. Data suggests that the shrink-swell Rincon sediment portrays different behavior in drying than that which occurs for a non-shrink-swell soil. For the shrink-swell Rincon sediment, thermal conductivity is seen to increase with decreasing moisture, the suggested mechanism being increased surface area contact between particles as the shrinking sediment dries.
Cramer, Nicholas C. (2006). Thermal properties of an upper tidal flat sediment on the Texas Gulf Coast. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from