ABSTRACT
Percolate soil water samplers, including the pan and wick types, rely on gravity and/or capillary action to intercept both matrix and preferential flow from precipitation or irrigation wetting fronts. Other advantages of percolate soil water samplers include larger sample volumes, no need for a continuous vacuum, less potential for losing volatile compounds, and greater confidence with fewer samples, as a 70% confidence level is obtained with half the number of samples required for tension samplers. Site operations may be hindered by the installation and operation of soil water samplers and cause sample bias. The exact cleaning procedure proposed for soil water samplers for a given site should be specified in the approved quality assurance/quality control (QA/QC) plan and rigorously followed. Quality assurance/quality control for soil water samplers must be done in accordance with the QA/QC plan that governs soil water sampling at a particular site.
