Injection/recovery lysimeter technique for unsaturated zone soil-water extraction

Abstract

Current methods of vacuum lysimetry only allow water samples to be collected from the unsaturated zone in relatively wet soils. This thesis presents the results of computer simulation and field testing of a promising new technique that allows water samples to be collected regardless of antecedent moisture content. Injection of a chemically neutral fluid will increase the moisture content of a relatively dry soil, allowing the collection of a sample that contains soil water diluted in the injection fluid. This can be analyzed to yield qualitative chemical data. Although injection was found to alter soil structure and soil-water chemistry in some instances, the technique can be used in existing lysimeters, without modification, to repeatedly obtain partially representative soil-water samples containing inorganic and organic compounds. Injection lysimetry is best suited to those applications, such as tracer tests and detection of containment leakage, where absolute chemical concentrations are not required.