A Three-Dimensional Field Study of Solute Transport Through Unsaturated, Layered, Porous Media 1. Methodology, Mass Recovery, and Mean Transport

A field experiment is reported which monitored the three-dimensional movement of cubic solute plumes through an unsaturated, loamy sand soil. The plumes were created with one of two methods, a two-dimensional flux application and an initial resident distribution. Soil coring was used to sample resident concentrations for the three solutes studied. The data were analyzed using the method of moments. In addition to the solute transport experiments, a detailed set of physical properties of the field was obtained by excavating three pits to a depth of 5.0m and also by taking soil cores throughout the study area. This paper explains the experimental methodology, summarizes the relevant site characteristics, and describes the observed transport based on the zeroth and first order spatial moments. Mass balance varied between 78 and 138%. The field-averaged gravimetric water content and dry bulk density were used to accurately predict the mean vertical plume displacement. These plumes spread relatively little in the horizontal direction