A Comparitive Analysis of Boundary Layer Methods in Solving Convectiondispersion Equation of Solute Transport
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S153.5

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Supported by the Chinese Academy of Sciences Strategic Priority Program(No. XDA23070202)

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    Abstract:

    [Objective] Understanding the behaviours of solute transport in soils is of great importance to agricultural management, resource utilitzation and environmental protection. Introducing boundary-layer theory to solve solute transport problems provides a simple and accurate alternative method to predict solute profile distribution and estimate transport parameters. Appropriate selection of boundary layer solutions requires an overall understanding of the characteristics of boundary layer solution accuracy under different conditions.[Method] This study compared the accuracy of the polynomial solution, exponential solution, combined solution, logarithmic solution and small flux solution based on multiple parameter combinations. Solute front movement with time in soil column experiments was further used to evaluate the performance of boundary layer solutions for parameter estimation.[Result] The accuracy of boundary layer solutions for predicting solute concentration profile increased first and then decreased with time. Comparison of different boundary layer solutions indicated that the cubic polynomial solution was optimal at the beginning while the exponential solution turned to be better afterwards for most cases. Importantly, the boundary layer methods performed better in estimating retardation factor than dispersion coefficient. The retardation factor obtained from boundary layer solutions was almost the same but with an exception of the small flux solution. The dispersion coefficient was greater than the breakthrough curve fitting method and varied between boundary layer solutions. The cubic polynomial and logarithmic solutions had a minimum error in the determination of the dispersion coefficient.[Conclusion] Boundary layer solutions can be used to accurately predict solute profile distribution for the early stage of solute transport processes. Cubic and exponential solutions had better performance than other solutions. Neverthless, cubic and logarithmic solutions can be the first choice for estimating parameters.

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WANG Jiao, SHAO Ming'an. A Comparitive Analysis of Boundary Layer Methods in Solving Convectiondispersion Equation of Solute Transport[J]. Acta Pedologica Sinica,2022,59(4):964-974.

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History
  • Received:September 24,2020
  • Revised:August 27,2021
  • Adopted:October 19,2021
  • Online: October 20,2021
  • Published: April 11,2022