Geochemical monitoring of thermal waters in Slovenia: relationships to seismic activity

Extremophilic Microorganisms in Central Europe

Extremophiles inhabit a wide variety of environments. Here we focus on extremophiles in moderate climates in central Europe, and particularly in Slovenia. Although multiple types of stress often occur in the same habitat, extremophiles are generally combined into groups according to the main stressor to which they are adapted. Several types of extremophiles, e.g., oligotrophs, are well represented and diverse in subsurface environments and karst regions. Psychrophiles thrive in ice caves and depressions with eternal snow and ice, with several globally distributed snow algae and psychrophilic bacteria that have been discovered in alpine glaciers. However, this area requires further research. Halophiles thrive in salterns while thermophiles inhabit thermal springs, although there is little data on such microorganisms in central Europe, despite many taxa being found globally. This review also includes the potential use of extremophiles in biotechnology and bioremediation applications.

Hydrogeochemical Characterization of a Warm Spring System in a Carbonate Mountain Range of the Eastern Julian Alps, Slovenia

The Alps represent an area where many deep groundwater circulations occur as thermal springs. In the Bled case study, the thermal water temperature, at it is discharged to the surface, is between 19–23 °C. In order to determine the extent (e.g., geometry) and the origin of the pronounced deep circulation system in the Bled area, chemical and isotopic measurements of waters from different hydrogeological systems were performed (e.g., surface water, thermal water, fresh groundwater). Hydrogeochemical methods were used to tie together the above-mentioned parameters. The results have shown that thermal outflow in Bled is determined by the presence of a deep-water circulation system, where the dissolution of carbonates minerals is the main hydrogeochemical process affecting chemical components of natural water flow. The correlation of the major ions suggests that the recharge area is represented by both limestone and dolomite rocks. Moreover, the results of δ18O and δ2H of all samples indicate that the recharge is mainly meteoric precipitation. The recharge altitude was estimated for two sampled fresh groundwater springs. The isotopic compositions of those two springs suggest the range from δ18O = −8.68‰, δ2H = −57.4‰ at an elevation of 629 m to δ18O = −9.30‰, δ2H = −60.1‰ at an elevation of 1216 m. The isotopic analysis has confirmed that the thermal water recharges from altitudes of 1282–1620 m a.s.l.

Hydrogeochemical and isotopic tracers for identification of seasonal and long-term over-exploitation of the Pleistocene thermal waters

The aim of the study was to develop and test an optimal and cost-effective regional quality monitoring system in depleted transboundary low-temperature Neogene geothermal aquifers in the west Pannonian basin. Potential tracers for identification of seasonal and long-term quality changes of the Pleistocene thermal waters were investigated at four multiple-screened wells some 720 to 1570 m deep in Slovenia. These thermal waters are of great balneological value owing to their curative effects and were sampled monthly between February 2014 and January 2015. Linear correlation and regression analyses, ANOVA and Kolmogorov-Smirnov two-sample test for two independent samples were used to determine their seasonal and long-term differences. Temperature, pH, electrical conductivity, redox potential and dissolved oxygen did not identify varying inflow conditions; however, they provided sufficient information to distinguish between the four end-members. Characteristic (sodium) and conservative (chloride) tracers outlined long-term trends in changes in quality but could not differentiate between the seasons. Stable isotopes of δ (18)O and δ (2)H were used to identify sequential monthly and long-term trends, and origin and mixing of waters, but failed to distinguish the difference between the seasons. A new local paleo-meteoric water line (δ (2)H = 9.2*δ (18)O + 26.3) was outlined for the active regional groundwater flow system in the Pannonian to Pliocene loose sandstone and gravel. A new regression line (δ (2)H = 2.3*δ (18)O-45.2) was calculated for thermomineral water from the more isolated Badenian to Lower Pannonian turbiditic sandstone, indicating dilution of formation water. Water composition was generally stable over the 1-year period, but long-term trends indicate that changes in quality occur, implying deterioration of the aquifers status.

Radon in a thermal spring: Identification of anomalies related to seismic activity

Anomalies have been observed in the radon content of thermal spring water at the Italian-Slovenian border. To distinguish the anomalies caused by environmental parameters (air and water temperature, barometric and hydrostatic pressure, rainfall) from those ascribed solely to earthquakes with M(L) from 1.2 to 2.5 and epicentres, R(E), within 2R(D) (R(D)--Dobrovolsky's radius), two approaches have been used: (i) correlation between time gradients of radon concentration and hydrostatic pressure, and (ii) regression trees within machine learning programs. The regression trees approach has been improved by introducing additional environmental parameters and prolonging the measuring period.

Application of decision trees to the analysis of soil radon data for earthquake prediction

Different regression methods have been used to predict radon concentration in soil gas on the basis of environmental data, i.e. barometric pressure, soil temperature, air temperature and rainfall. Analyses of the radon data from three stations in the Krsko basin, Slovenia, have shown that model trees outperform other regression methods. A model has been built which predicts radon concentration with a correlation of 0.8, provided it is influenced only by the environmental parameters. In periods with seismic activity this correlation is much lower. This decrease in predictive accuracy appears 1-7 days before earthquakes with local magnitude 0.8-3.3.