Modelling of Pollutants Dispersion in Groundwater

 للكاتب :

Y. R. Fares

The British University in Egypt, Faculty of Engineering

Sherouk City, Cairo-Ismailia Road, Cairo, Egypt

Abstract

A numerical model capable of predicting the dispersion of pollutant discharges along a

homogeneous aquifer is presented. The advection-dispersion equation (ADE) is utilised in

predicting the concentration levels for cases of continuous and instantaneous release modes.

The Crank-Nicholson equation is employed in the presented model and the solution is carried

out using the implicit Gauss-Seidel method with over- and under-relaxation coefficients,

depending on the state of convergence. The performance of the numerical scheme has

improved significantly by removing the zero- and first-order truncation errors in the ADE

with a reaction term. The computed concentration profiles are compared with measured

values for cases of non-reactive (tracer) and reactive (organic) solutes with continuous

injection in homogeneous isotropic soils. The analysis of results has shown that for the case of

non-reactive solutes, reliable simulations are produced. While for the case of solutes

undergoing adsorption, accurate concentrations can be predicted by adjusting the influent pore

water velocity by using a retardation factor, which is suitable for aquifers with low organic

carbon content and undergoing hydrophobic partitioning. Finally, the mechanisms relating to

the soil/pore water interactions, such as ion exchange, chemi-sorption and physic-sorption,

can be embraced in the model for simulating dispersive reactive solutes within the saturated

zone.

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