A bromide tracer was applied on a 2.2 m long and 0.4 m wide plot at the location of a hydrophobic soil in the southwest of The Netherlands. At the end of the experiment, the plot was excavated to a depth of 0.7 m using 100 cm3 samples, yielding a total of 1680 samples to quantify the three-dimensional spatial distribution of water content, pH, bromide concentration and degree of water repellency. Measured water content and solute distributions indicated that unstable (fingered) flow prevails. It is considered that contaminant transport under such conditions can proceed at rates that are higher than that which would normally occur if the flow were stable. This article illustrates an attempt at modeling contaminant transport under unstable flow conditions using measurements obtained from the experimental plot. A finite element solution of the two-dimensional Richards equation forms the basis for the unstable flow simulation, while a particle tracking random walk solution of the two-dimensional convection-dispersion equation forms the basis of the transport simulation. The water flow simulation and the solute transport simulation were compared with the measured data. Initial results indicate that model predictions compared fairly well with measured water content and solute transport data.
Bibliographical noteFunding Information:
Published as Paper No. 981120024 of the scientific journal series of the Minnesota Agricultural Experiment Station on research conducted under Minnesota Agricultural Experiment Station. This study was executed within the framework of (i) the Environment and Climate Research Program of the European Union, as part of the research project ‘Analysis and improvement of existing models of field scale solute transport through the vadose zone of differently textured soils with special reference to preferential flow’, and (ii) the Research Program 223 ‘Physical Soil Quality’ of the Dutch Ministry of Agriculture, Nature Management and Fisheries. The modeling part was supported by the Army High Performance Computing Research Center under the auspices of the Department of the Army, Army Research Laboratory cooperative agreement number DAAH04-95-2-0003/contract number DAAH04-95-C-0008, the content of which does not necessarily reflect the position or the policy of the government, and no official endorsement should be inferred. Collaboration on the research was supported by the NATO Collaborative Research Grant No. 960704.
- Hydrophobic soil
- Particle tracking method
- Preferential flow
- Solute transport
- Unstable flow