Capillary‐Wick Unsaturated Zone Soil Pore Water Sampler

Abstract

Existing unsaturated zone soil water samplers have several deficiencies that jeopardize their utility for field sampling. Suction cups function only when a vacuum is applied, and sample from an unknown volume of soil. Pan samplers sample only saturated flow. A capillary‐wick sampler was developed to overcome these problems and was tested in both the laboratory and field to evaluate its performance. Breakthrough curves for selected inorganic ions and organic chemicals were established in the laboratory. No adsorption/desorption of these chemicals was found for the capillary‐wick sampler made entirely of glass. Banks of eight capillary‐wick samplers were installed in field plots of Padina sand (loamy, siliceous, thermic, Grossarenic Paleustalf), Weswood silt loam (fine‐silty, mixed, thermic Fluventic Ustochrept), and Lufkin clay (fine, montmorillonitic, thermic Vertic Albaqualf) soils. Saturated soil Br breakthrough curves were determined at each location and used to estimate the number of samplers required to characterize the flow of contaminants. To achieve 95% confidence in the chemical data from the three soils and plot sizes tested, 31 samplers were required for the sandy soil, six for the silt loam soil, and only two for the clay soil. The wick‐activated sampler collected soil solution samples from soils having soil water potentials ranging from 0 to −6.0 kPa. The capillary‐wick sampler collected samples continuously across this range of water potentials without the need for a continuous vacuum and is thus an improvement over existing samplers. While the capillary‐wick samplers usually collected sample volumes representative of the flux at potentials of −5 kPa, samples collected at greater and lesser potentials were not representative of the flux.

Nitrogen Fertilizer Rate and Crop Management Effects on Nitrate Leaching from an Agricultural Field in Central Pennsylvania

“…Soil pH and other nutrients were maintained at optimum levels for all crops and recommended varieties and management were used to optimize yields. In 1995, eighteen 0.3 × 0.3 m wick lysimeters based on the design of Holder et al [6] were installed at the 1.2 m depth in tunnels on the opposite side of the access pits [5]. The wicks were placed such that there was up to 0.5 m water tension on the lysimeter surfaces.…”

Water and Bromide Recovery in Wick and Pan Lysimeters under Conventional and Zero Tillage

“…Zhu, Fox, and Toth (2002) attributed the oversampling by wick lysimeters to the possibility that the samplers were behaving as sinks, when more drainage had been recorded than precipitation observed during a very wet 1997 season. Holder et al (1991) attributed this overestimation of drainage to converging flow lines toward the sampler when water potential was high, describing the wick sampler as a possible sink.…”

Evaluation of fast growing tree water use under different soil moisture regimes using wick lysimeters

“…Among different possible sources of raw material for bioenergy production, short-rotation plantations can be a valuable choice for marginal land where conventional agriculture is not effective (Gupta & Mohan 1982). In our work we investigated the tree species black locust (Robinia pseudoacacia L.), widely used for short-rotation forestry and agroforestry systems for biomass production in East Germany and Hungary (Tsakov & Alexandrov 2005, Rédei & Veperdi 2009, Grünewald et al 2009.…”

“…They further require high technical maintenance; in addition the pumps need power supply, which is a supplementary impediment, when the installation is in secluded areas. An acceptable compromise between the two extremes of lysimeter typology is the tension controlled wick lysimeter (Weihermüller et al 2007), where the stagnancy is avoided by constant suction performed by a hanging water column through the wick material (Holder et al 1991, BenGal & Shani 2002. The improved drainage efficiency of the wick lysimeter against the zero-tension lysimeter has already been described in a critical comparison (Zhu et al 2002, Mantovani et al 2011).…”