10.4122/1.1000000733
Tsakiroglou, Christos
Christos
Tsakiroglou
ctsakir@iceht.forth.gr
Tzovolou, Dimitra
Dimitra
Tzovolou
dtzovol@iceht.forth.gr
Aggelopoulos, Christos
Christos
Aggelopoulos
caggelop@iceht.forth.gr
Theodoropoulou, Maria
Maria
Theodoropoulou
mtheod@iceht.forth.gr
Dalkarani, Theodora
Theodora
Dalkarani
dalkarani@teipat.gr
Pikios, Constantinos
Constantinos
Pikios
pikios@teipat.gr
Tsakiroglou, Christos
Christos
Tsakiroglou
ctsakir@iceht.forth.gr
Solute dispersion coefficients in heterogeneous porous media as related with the migration of pesticides in groundwater
XVI International Conference on Computational Methods in Water Resources
2006
2006
During the last years, too much attention has been focused on problems related with
the diffuse pollution of groundwater by pesticides. However, in spite of the
numerous lab-scale and field-scale experimental studies and numerical approaches,
one significant factor is usually overlooked: the transverse and longitudinal
dispersivities are scale-dependent and sensitive to the variation of microscopic
properties of the pore structure and multiscale heterogeneities.
Miscible displacement and single source-solute transport experiments are performed
on long columns of disturbed soils of broad grain size distribution. The
geometrical and topological parameters of the pore space of soils are estimated by
fitting the experimental mercury intrusion/retraction curves to analytical
percolation models of the processes. The breakthrough curves of the tracer (NaCl)
concentration along the column is monitored by measuring the electrical resistance
at various axial positions from the column entrance. An inverse modeling algorithm
based on a Bayesian estimator is used to fit the experimental data to adequate
analytical and numerical solutions of the advection dispersion equation to estimate
the dispersion coefficients as functions of the pore structure heterogeneity, and
Peclet number. Moreover, this information is used to develop relevant
phenomenological models of the longitudinal and transverse dispersion coefficients.
Then, a 2-D macroscopic numerical model of the transport / sorption /
biodegradation of pesticides in heterogeneous porous media is developed in the
environment of flex-PDE (solver of partial differential equations with finite
elements) to simulate long-term fate of pesticides in groundwater. Sample
simulations are done by using literature and laboratory data concerning the
physicochemical and transport properties of four pesticides (glyphosate, phorate,
mancozeb, and 2,4-D) that are widely utilized in agricultural cultivations of
Western Greece. The simulator is employed to investigate the potential errors
caused on (1) the long-term predictions of the fate of pesticides in aquifers, and
(2) the interpretation of lab-scale mobility experiments of pesticides, when
incorrect values of dispersion coefficients are used as input data.