Design and Evaluation of a Ceramic Candle and Trough Soil Moisture Sampler for use in Sandy Soil
Rainey, Michael W.
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Various tension lysimeters have been employed to quantify the loss of soluble soil constituents from the vadose zone. Typically, ceramic cup samplers have been the most widely used. However, conventional ceramic cup samplers proved highly unreliable for collecting soil moisture from sandy soils in Portage County. The objective of this research was to develop and evaluate a more reliable sampler for use in sandy soils. Theoretically, the ceramic candle and trough sampler of Duke and Haise (1973) seemed more suitable. Their design was modified to reduce cost and complexity. The resulting sampler consisted of a combination porous, ceramic candle extractor and a 6 ft. long and 6 in. wide PVC trough. This sampler was evaluated both in the field and laboratory. In addition, prepared standard solutions were drawn through ceramic candles to observe changes in water quality. Candle tests demonstrated the ability of ceramic candles to absorb and desorb ions as water passes through the ceramic filter. Candles can reach equilibrium, but significant changes in ionic concentration or composition reactivate adsorption/desorption reactions. In the field candle/trough samplers were 82% reliable in extracting soil water. However, the divergence of water around the trough reduced the recovery of gravitational flow. Field studies also identified significant in-treatment variability induced by this sampling device. Laboratory research verified low percent recovery of gravitational water. Low moisture recovery, possibily augmented by the ionic absorption of ceramic candles, resulted in a 20% reduction of overall ionic concentration for collected samples compared to ambient concentrations.