Origin of fluorine in mineral waters of Bujanovac valley (Serbia, Europe)

This paper deals with mineral and thermomineral water occurrences of the Bujanovac valley in south eastern part of Serbia related to granitoides of the Bujanovac massif along both the margin and the floor of the valley. In past decades (1966–2010) numerous hydrogeological, hydrogeochemical and geophysical explorations were carried out. One of results of these explorations is the completion of test holes and exploratory—production wells. They provide groundwater for three water bottling factories: “Heba”, “Bivoda”, “Prohor” as well as the “Vrelo Bujanovac Banja Spa Centre” for rehabilitation, treatment, and prevention. All stated consumers use the same mineral water aquifer. The content of fluoride in the majority of examined mineral waters is higher than 4 mg/1, whereby they are singled out as typical fluoride waters. The content of calcium ions in them amounts 80 mg/1, and the values of the saturation index in relation to calcium fluoride (SI) range from 0.4 to 0.7 mg/1, which points to mineral waters saturated in relation to fluorite. However, in the study area, there are mineral water occurrences with the content of fluoride significantly lower than in the majority of analysed waters representing hydrochemical anomalies. These waters occur as hydrochemical anomalies in marl and sandstone wherein Secondary mineral water aquifers, originating from cracked granite of the Bujanovac massif, are formed. When mineral waters from granite (with the increased content of fluoride) reach these secondary aquifers, the content of fluoride ions lowers to about 1 mg/1, which is of great significance from the point of view of mineral water utilisation as table bottled water. In this paper, it is proved that, in addition to the presence of some minerals as basic fluorine bearers, the role of the lithological environment where the natural process of defluoridation occurs is significant, which is confirmed by the revitalization of the A-4 well. The paper deals with mineral water deposits of the Bujanovac valley, and the natural way of lowering of fluorine content in the given waters.