WICK SAMPLERS

Abstract

Wick samplers have the potential to improve solute sampling in the vadose zone, but more information is needed about the effect of soil-wick sampling interface disturbances on measured fluxes and solute concentrations. The objective of this paper is to examine how the wick sampler alters the matric potential, streamlines, and solute concentrations in the native soil. Both theoretical analysis and experimental studies were performed. An equation for travel time was developed that included the effect of changes in moisture content in the soil when a wick sampler is installed. Experimental measurements of pressure head near the soil-wick interface were taken, and a travel time moment analysis of narrow solute pulses was conducted for several steady flow experiments. Model and theory agreed well and showed that even when the capillary length α−1 is similar in the soil and wick, dissimilarity of the hydraulic conductivity and cross-section flow area may significantly affect soil moisture content above the soilwick interface and on the solute pulse travel time. It was also found that in many cases solute pulse travel time was affected more by the pressure head changes that occurred at the soil-wick interface than by the flow through the wick.