Advancements in pipe monolith lysimeter designs

The self-contained field lysimeter, patented by ABC Laboratories, Inc. (U.S. Patent # 5,594,185) has been used to test the mobility and dissipation of various agrochemicals in a variety of field sites and soil types. In this paper we present data to support the functionality of the pipe lysimeter design and describe some recent design modifications that have been made to improve its performance. The previous design, presented at the ASTM Eighth Symposium on Environmental Toxicology and Risk Assessment, Atlanta, Georgia, April 1998, used a steel soil core casing, which for some test substances could result in unwanted wall sorption or catalyzed degradation. The use of a stainless steel core casing, while generally considered to be inert for most test substances, can become very expensive, increasing the overall cost of the field project. For these reasons, the modular lysimeter design was modified to allow the use of PVC and other non-metallic soil core casing materials. The utilization of non-metallic soil core casing materials requires the use of a custom manufactured cutting tip and pressing ring for generation of the soil core. Other significant modifications include enhanced methods for the leachate and over-flow module attachment to the soil column, and the instrumentation used for the leachate collection void at the base of the soil column. Development of the monolith lysimeter design to include non-metallic soil core casings provides a comprehensive method for use of all potential core casing materials in the generation of intact, undisturbed soil columns. Benefits of the PVC lysimeter modification include minimal compaction during soil-core generation, chemically inert casing materials for some test substances, and reduced materials costs. In addition, the instrumentation scheme used for the PVC lysimeter allows for more pre-fabrication prior to field deployment, and minimal labor requirements in the field for instrumentation and installation, significantly reducing the overall cost of field lysimeter projects.