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AN APPROXIMATE SOLUTION TO THE CONVECTION-DISPERSION EQUATION OF SOLUTE TRANSPORT IN SOIL1.

Shao, M.2; Horton, R.3; Miller, R. K.4

Technical Articles

This paper uses a boundary-layer method to solve the convection-dispersion equation (CDE) to predict solute transport in soil. The boundary-layer solution describing chemical transport for a semi-infinite soil column or field soil profile has the advantages over the corresponding exact solution of simplicity in expression and flexibility in manipulation. Comparisons of the boundary-layer solution to the exact solution are conducted for a range of parameter values. Results show that the boundary layer solution is in good agreement with the exact solution. An important application of the boundary-layer solution is the estimation of transport parameters of solute movement through soils under both laboratory and field conditions. This leads to a new method for estimating parameters of solute transport in soils. The new method requires observation of the advance of the depth of boundary layer (solute front) with time. This can be done visually by using a tracer solution with dye in it. The new method is simple, saves time, and is applicable to both laboratory soil columns and field soils.

1Contribution as Journal paper no. J-17033 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Projects no. 3262 and 3287, and supported by the Hatch Act and State Funds.

2Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shaanxi, China, 712100.

3Dept. of Agronomy, Iowa State Univ., Ames, IA 50011. Dr. Horton is corresponding author. E-mail: rhorton@iastate.edu

4Dept. of Mathematics, Iowa State Univ., Ames, IA 50011.

Received July 14, 1997; accepted January 5, 1998.

© Williams & Wilkins 1998. All Rights Reserved.