Fórizs, I., Kuti L., Tóth, T. 2004. Isotope hydrological study of soil salinization 
in a sodic grassland on the Hortobágy, Hungary. Berichte des Institute für 
Erdwissenschaften Karl-Franzens-Univeersitat Graz. 8:30-34

One of the most characteristic native sodic grassland of Hungary, the Nyírolapos, a small
area of 600x800 m site on Hortobágy (Great Hungarian Plain) was selected for studying the salt
accumulation in the soil by different methods: water level observation, soil bulk electrical
conductivity (ECa), water chemistry, and stable oxygen and hydrogen isotope analyses. Water
samples were taken from monitoring wells at 9 points in every month for chemical analysis.
During the sampling campaign of 5 June 2002 water samples were taken for stable isotope
measurements as well. At five out of nine points three wells were installed for monitoring water
at different depths. The bottoms of the shallowest wells are at two meters below the water table
(usually 3-4 meters below the ground surface). The bottoms of the medium deep wells are at
about 6 meters below the ground surface, and the bottoms of the deepest wells are at about 10
meters below the ground surface.
The water infiltrated from a precipitation which originated from a place where the relative
humidity of air was high, or the infiltrating water suffered evaporation effect during the
infiltration. Both can be imagined during the Ice Age, because the climate was cold and dry. The
water line of the samples of the studied area is a mixing line, where the old ascendingwater mixes
with the infiltrating water from the modern precipitation. The spatial distribution of mixing ratio
is not homogeneous. The flux of the upwelling water is maximum, where the permeability of the
alluvial sedimentary layers is highest. At some sites the d18O values of the deeper water samples
are less negative than that of the shallowest one, while at other sites this relation is the opposite,
indicating a very complex mechanism of the mixing process.