Design and Evaluation of a Ceramic Candle and Trough Soil Moisture Sampler for use in Sandy Soil
Abstract
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.