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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of a Simple Method for Estimating Solute Transport Parameters: Laboratory Studies

Authors
item Lee, J - IOWA STATE UNIVERSITY
item Jaynes, Dan
item Horton, R - IOWA STATE UNIVERSITY

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 20, 2000
Publication Date: March 5, 2000
Citation: Lee, J., Jaynes, D.B., Horton, R. 2000. Evaluation of a simple method for estimating solute transport parameters: Laboratory studies. Soil Science Society of America Journal. 64:492-498.

Interpretive Summary: Scientists have a wide array of computer models for predicting the fate and transport of agrichemicals applied to soil. Before these models can be accurately applied to specific situations, the parameters required for the model need to be measured or estimated for the specific soil of interest. One group of models, that is very useful for estimating rapid movement of water and chemicals through preferred pathways in the soil, has been little used outside of the laboratory because of the difficulty in measuring the required model parameters. This research validates a new method for measuring these parameters that is easy, quick, and adaptable for use in the field. We show that the new method gives model parameter estimates that are as reliable as the more traditional, but time consuming measurement method. Now that the new method has been validated, scientists will be able to use the method with confidence in estimating parameter values for soils of specific interest. The method will allow more accurate modeling of water and chemical transport through soils and better estimates of ground water contamination by agrichemical use.

Technical Abstract: A two-domain, physical nonequilibrium solute transport model contains the parameters immobile water content and mass transfer coefficient which must be determined for a soil before applying the transport model. The purpose of this paper was to test in laboratory soil columns a simple method of estimating parameters by comparing it to the conventional BTC analysis method of parameter estimation. The experiments involved 12-cm-long and 4-cm-diam. columns packed with five different soil materials. The BTCs were performed on each column using a sequential application of four fluorobenzoate tracers. Each tracer was applied for a different length of time. The soil columns were sectioned at the end of the BTC experiments. The simple method gave results of immobile water content and mass transfer coefficient based upon the sectioned soil samples, and the BTC analysis gave results of immobile water content and mass transfer coefficient based upon effluent concentrations. Most of the estimated mass transfer coefficient values using the simple method were within the 95% confidence interval (CI) of the BTC estimates. For 7 of 10 soil columns, the estimates of immobile water fraction, from the simple method were within the 95% CI of the estimates obtained from BTC data. The simple method provides estimation of immobile water content and mass transfer coefficient from easy to obtain soil samples in the field.

Last Modified: 12/22/2014
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