Finite mass diffusion through soil: a 1D application
Jonathan Tenório de Lima1; Michelle Matos de Souza2; Maria Claudia Barbosa2
1 IRD/CNEN; 2 COPPE/UFRJ
Baixar PDF doi:10.20906/CPS/CB-05-0072
Resumo
A great challenge for scientists and engineers who work in the field of geoenvironmental engineering is to simulate accurate finite mass contaminant transport in soil. This is so because most of the models (analytical and numerical) used take into account an infinite mass source of contamination, which is far easier to represent. Commercial software, capable of handling finite mass, are available, but can be an extra expense in a short-budget project or even for simplified analysis. Analytical solutions are not always possible to obtain, nevertheless, if existent they can deliver an accurate response, however, they can be time consuming and delay the project schedule. Beyond that, analytical solutions are not readily workable and many times one must implement a new solution for each change in project instead of simply changing values. This work provides a free numerical solution to easily solve the parabolic 1D partial differential equation (PDE) for reactive diffusion transport in soil. Reactions are represented by adsorption isotherms such as linear, Freundlich and Langmuir. The numerical code is based on the assumption that mass flow through the soil top surface concur to decrease the concentration in the overlying reservoir. In this case, a first-type boundary condition may be assumed on top of the soil layer while an impermeable boundary condition (second-type) is set at the bottom according with experimental set up. The code was written in FORTRAN 90 syntax and compiled with GCC/GNU free platform for windows MINGW. It uses a forward in time and centered in space (FTCS) numerical scheme which can be easily reproduced even in a standard personal computer. Here, the numerical code was tested to calibrate experimental data and to evaluate its capability and was proven feasible. The tests used are the result of a previous work on the diffusion transport of potassium chloride in a processed kaolin clay soil. This soil was commercially acquired and has been though processed by the company following ceramic and pap
Palavras-chave: finite mass; contaminant transport; FDM