『Abstract
The semi-confined Ledo-Paniselian (Eocene) Aquifer in Flanders,
Belgium is recharged in the areas with higher topography, where
it is covered by the Bartonian Clay. Initial conditions in these
sediment were marine. Hydrogeochemical modelling of the groundwater
type distribution in the aquifer with a reaction transport model
considers recharge of fresh CaHCO3 water』
by downward flow through the overlying clay. In the aquifer, in
an upstream direction, progressively more freshened water types
are found. A typical NaHCO3 type occurs upstream
of the brackish-fresh water interface. The different stages of
cation exchange produce a chromatographic sequence of groundwater
types, which agrees well with observations. Cation exchange processes
occurring mainly in the percolated clay, result in a Na+
increase, and peaks of K+, NH4+
and Mg2+ in the aquifer, which are spatially separated
as a result of groundwater flow. Calcite equilibrium, gypsum dissolution
in the clay and sulphate reduction in the aquifer have also been
included in the modelling.』
1. Introduction
2. Geology and hydrogeology of the Ledo-Paniselian Aquifer
3. Hydrogeochemical evolution
4. Exchangeable cations in the Bartonian Clay and exchange parameters
5. Geochemical modelling of freshening of the Bartonian Clay and
Ledo-Paniselian Aquifer - Development of a chromatographic pattern
5.1. Hydraulic schematization
5.2. Chemical model
5.3. Freshening of the Bartonian
5.4. Freshening of the Ledo-Paniselian Aquifer
5.5. Freshening of the aquifer in the northern part
6. Conclusions
Acknowledgements
References