Abstract form

Groundwater under salt affected soils
Barbara KERÉK*, László KUTI, Ubul FÜGEDI
Department of Environmental Geology, Geological Institute of Hungary
*Corresponding author’s e-mail: kerek@mafi.hu
The project on studying changes in groundwater chemistry started in 1995 at the
Nyírőlapos model area, Hortobágy. After the first results, it became clear that the
regular observations have to be extended to other model areas. Between 1995 and 2004
new observation wells were located in different parts of the Great Hungarian Plain (in
two bigger salt-affected plains: Hortobágy and Apajpuszta; others in the smaller saline
lakes at Fülöpszállás, Fülöpháza, Bugac, Csólyospálos, in the Danube-Tisza Interfluve).
At some locations the observation is available from different depths at the same place.
Wells are monthly sampled and groundwater level, conductivity and pH are measured in
the field. Water samples are filtered and conserved, then they are analysed in the Water
chemistry Laboratory of the Geological Institute of Hungary. Total water analysis (Na,
K, Ca, Mg, Fe, Mn, NH4, Cl, SO 4 , HCO 3 , NO 3 , NO 2 , hardness, alkalinity, total soluble
salt content), and microelement determination (Cr, Zn, Co, Ni, Ba, AL, Cu, Sr, Mo, B,
Pb, Cd, Li) are completed on every water samples. Based on our results, in some
extremely salt affected areas not just the concentration of the groundwater changes, but
its chemical composition too.
Precipitation has a great importance in the changes of the salt content in the
groundwater. Rainwater, fallen on the surface, infiltrate into the geological media and
going through the layers above the groundwater, can dissolve significant amount of
soluble salt and transport them to deeper layers. Poorly permeable layers on the surface
hinder or slow down the filtration of precipitation into the groundwater, so the leaching
effect of percolating rainwater cannot or just partly can predominate. Evaporation
clearly increases salt concentration in groundwater, and if the groundwater becomes
saturated in any compound, its precipitation alters the chemical composition of the
groundwater.
Changes in groundwater chemistry could also be caused by lateral water movements
and inflow. Groundwater level above see level in wells at Nyírőlapos-model area shows
that lateral groundwater flow has to be taken into account even in absolutely flat areas.
The flow direction can sometimes reverse. The groundwaters of the areas close to each
other have different chemical composition and concentration, so they can be mixed up
by lateral water flow.
The composition of the groundwater is influenced by meteorological factors, the
thickness-, the rock development-, and the quality of the layers above the groundwater
level. These factors influence the chemistry of the infiltrating rainwater and the
chemical composition of the groundwater changes, too.
Key words: groundwater, salt affected soils, changes in chemical composition
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