A case-study of complex gas–water–rock–pollutants interactions in shallow groundwater: Šalek Valley (Slovenia)

The complex geochemical interactions in the
groundwater of the industrial area of S ˇ alek Valley
(Slovenia) between natural and anthropogenic fluids were
studied by means of major (Ca, Mg, Na, K, HCO3
-, Cl-
and SO4
2-) and trace elements’ (As , Cd, Cu, Pb, Zn, Hg,
Se and V) abundances, geochemical classification and
statistical analysis of data. Cation abundances indicate
mixing between a dolomitic end-member and an evaporitic
or geothermal end-member. Anion abundances indicate
mixing between bicarbonate waters and either sulphateenriched
waters (suggesting hydrothermalism) or chlorinerich
waters. Principal component analysis (PCA) allowed
the extraction of seven factors, which describe, respectively:
water–rock interaction mainly on dolomitic rocks;
redox conditions of water; Cd–Zn enrichment in chlorinerich
waters (probably from industrial wastes); hydrothermal
conditions in waters close to major faults; Pb and Cu
pollution; V and K enrichments, indicating their common
organic source; the role of partial pressure of CO2
dissolved in water, which is highest in three wells with
bubbling gases. Average underground discharge rates of
solutes from the Valley range between 0.09 t/a (V) and
1.8 9 104 t/a (HCO3
-) and indicate how natural fluids can
significantly contribute to the levels of elements in the
environment, in addition to the amount of elements
released by human activities.

Ministry of
Foreign Affairs of Italy and Ministry of Superior Instruction,
Science and Technology of Slovenia.
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo

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