Computational & Technology Resources
an online resource for computational,
engineering & technology publications 

CivilComp Proceedings
ISSN 17593433 CCP: 80
PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: B.H.V. Topping and C.A. Mota Soares
Paper 11
Numerical Methods for Modelling Leaching of Pollutants in Soils and Groundwater M.I. Asensio+, L. Ferragut+, G. Sangalli* and B. Ayuso*
+Department of Applied Mathematics, University of Salamanca, Spain
M.I. Asensio, L. Ferragut, G. Sangalli, B. Ayuso, "Numerical Methods for Modelling Leaching of Pollutants in Soils and Groundwater", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Fourth International Conference on Engineering Computational Technology", CivilComp Press, Stirlingshire, UK, Paper 11, 2004. doi:10.4203/ccp.80.11
Keywords: mathematical modelling, convectiondiffusionreaction, stabilized finite element, residualfree bubbles, pollutants leaching.
Summary
Pesticides used in crop production and herbicides used for weed
control are the major source of nonpointsource pollutants to
groundwater. Their discharge to the surface water may be a
contributing factor toward the decline of the living resources and
the deterioration of ecosystems. In fact, the raising presence of
this kind of pollutants in the aquifers with high concentrations
has become a serious environmental problem.
Physicallybased environmental simulation models can be costeffective tools as an alternative to costly and prolonged field monitoring strategies. Environmental fate and transport simulation models vary in their complexities and purposes. The more complex the model is, the more comprehensive in the level of detail, but their use, in practice, may be hampered by lack of sufficient data that justify their complexity. Leaching of pollutants (pesticides, herbicides, etc.) in soils and groundwater is a complex process. Agricultural practices, soils properties, climatic conditions are some of the most important aspects to be considered. Several simulation models, more or less complex, have been developed and used by several authors in order to simulate the behaviour of soil and aquifers for the chosen pollutants (see [1] and [2] as examples). A summary of several models and its theoretical basis can be found in [3] and [4]. The two models studied in this paper are a linear equilibrium and a linear non equilibrium adsorption models based on the onedimensional convection diffusion equation. The models account for processes such as diffusive mass transfer, biochemical degradation, crop uptake, volatilization, linear equilibrium adsorption and gravity drainage. The mathematical problem to be solved is an unsteady linear convectiondiffusionreaction onedimensional problem. The use of a numerical method to approximate the solution this problem allows to solve different problems modifying the initial, boundary and physical conditions, and it is a first step for future works dealing with more realistic multidimensional problems. Most of the previous works on leaching of pollutants simulations use analytical solutions of much simpler models. As an example, in [5] integrated massbalance equations are used to approximate the average solute concentration on each zone (rootzone, vadosezone and groundwater) and then, the corresponding timedependent first order differential equation is analytically solved. The advantages of using a numerical approximation is that it may be generalized in a straightforward way to the case of different zones without simplifying assumptions. The main difficulty in the numerical approximation of this kind of partial differential equations, is the accurate modelling of the interaction between convective, diffusion and reaction processes. In this work we consider several stabilization techniques, including also the LinkCutting Bubble strategy recently proposed in [6]. As it will be shown by means of numerical experiments, this stabilization technique is the one that produces better results when approximating the problems derived from the models developed in this work. References
purchase the fulltext of this paper (price £20)
go to the previous paper 
