Abstract
In Hungary, 0.5 million m3 of thermal water is exploited every day for diverse purposes. After utilization, this enormous amount
of thermal water becomes sewage water with a high concentration of salts, heavy metals, ammonia, nitrate, an unfavorable ion
composition and high temperature. A common treatment is to dispose of waste water into a surface recipient through uninsulated
channels surrounded by arable land. By infiltration, sewage water can cause potential salinization/sodification/alkalinization and
contamination of soil and groundwater. This work investigates the manifestation of these problems in different soil types,
Chernozem, Phaeozem and Arenosol, representing case studies regarding the environmental risks of used thermal water.
The results conclude that seeping thermal water has a high Na+-concentration and salt content, which represents risk of soil
sodification/salinization, while leaching facilitates a rise in the salty groundwater table, and a change in the chemical type (Na+-
dominance) surrounding the channel. Together, these factors lead to soil degradation in the investigated Chernozem and
Phaeozem profiles. In Arenosol, the aforementioned processes were not observed, but infiltrating thermal water reached
groundwater adjacent to the channel and enhanced its total salt content and Na+-rate. Referring to the Chernozem and Phaeozem
soils, statistical analyses were carried out to determine the significant variation in soil properties between profiles located at
different distances from the channel. Via principal component analysis combined with discriminant analysis, Mg2+-mobilization
and salinization processes were identified near the channel. On the basis of the computed discriminant function, sample groups of
two localities (control and thermal water affected) can be unambiguously distinguished.