An Integrated Approach to Characterising Sulphur Karst Springs: A Case Study of the Žvepovnik Spring in NE Slovenia

We present an integrated approach to characterizing the Žvepovnik sulphur spring, comprising detailed basic geological (mapping), geochemical (physico-chemical, elementary), isotopic (δ2H, δ18O, δ13CDIC, δ34S and 3H), and microbiological analyses. We used a multi-parameter approach to determine the origin of the water (meteoric or deeper infiltration), the origin of the carbon and sulphur, and water retention times. Our special research interest is the origin of the sulphur, as sulphur springs are rare and insufficiently investigated. Our results show that the Žvepovnik spring occurs along the fault near the contact between the dolomite aquifer and overlying shales and volcanoclastic beds. The spring water is the result of the mixing of (1) deeper waters in contact with gypsum and anhydrite and (2) shallow waters originating from precipitation and flowing through the surface carbonate aquifer. The results of δ2H and δ18O confirm local modern precipitation as the main source of the spring. δ13CDIC originates from the degradation of organic matter and the dissolution of carbonates. We therefore propose four possible sources of sulphur: (1) the most probable is the dissolution of gypsum/anhydrite; (2) barite may be a minor source of sulphur; (3) the microbial dissimilatory sulfate reduction; and (4) the oxidation of pyrite as the least probable option.