ГЕОХИМИЯ, 2013, № 3, с. 229-244
ORIGIN OF FLUORINE IN MINERAL WATERS OF BUJANOVAC VALLEY
(SERBIA, EUROPE)
© 2013 г. O. Krunic", S. Parlic4, D. PolomCrc", M. Jovanovic4, S. Erie"
aFaculty of Mining and Geology, Djusina 7, Belgrade, Serbia e-mail: krunico@open.telekom.rs bNatural Mineral Waters, DZordZa Vasingtona 14/2, Belgrade, Serbia Поступила в редакцию 09.11.2011 г.
Принята к печати 20.02.2012 г.
Abstract —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/l, whereby they are singled out as typical fluoride waters. The content of calcium ions in them amounts 80 mg/l, and the values of the saturation index in relation to calcium fluoride (SI) range from 0.4 to 0.7 mg/l, 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 hydro-chemical 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/l, 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 litho-logical 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.
Keywords: fluorine content, micro components, lithological area, mineral waters, natural fluorine lowering
DOI: 10.7868/S0016752513010056
INTRODUCTION
In addition to macrocomponents determining the basic genetic type of mineral water, there are also significant microcomponents, present in small quantities, usually below 1 mg/l. They do not affect the type of mineral water by their presence, but impact on its specific composition. Fluoride ions have special position among microcomponents.
The fluoride concentration in groundwater depends on various factors such as: temperature, pH value, solubility of minerals being fluorine bearers, the anion exchange capacity of a water-bearing material (OH- for F), and the nature of geological formations the water passes through, as well as the periods of contacts with individual formations.
It is the minerals: fluorite, apatite, mica, amphibole, and some types of clay that have the highest im-
pact on the hydrochemistry of fluoride. Fluoride is a chemical constituent with upper (1.2 mg/l) and lower concentration limits (0.6 mg/l) in drinking water with identified health effects. Highly low fluoride content (<0.6 mg/l) in water contributes to tooth decay, namely caries causing effects. However, if water with higher content (>1.5 mg/l) is used, it causes dental fluorosis, namely enamel fluorosis, while high fluoride concentrations (>3.0 mg/l) can result in skeletal fluorosis. If fluoride content, taking into account its high biological activity in mineral water, exceeds 1 mg/l, it is categorized and put on sale as fluoride water.
The paper aims, on the basis of mineral water occurrences enriched by fluoride, in Serbia — the Bujanovac valley, to present characteristics of these water deposits and the origin of fluorine in the mineral water as a component that declares and limits the use of this water.
METHODOLOGY (SITE DESCRIPTION)
During explorations conducted in the period from the year 1966 to the year 2010, it was necessary to determine the values of numerous parameters such as: climatic, tectonic, geologic, hydrogeologic, geother-mal, hydrogeochemical, geophysical, etc. Within the research, there was also carried out the hydrogeologi-cal mapping of the Bujanovac valley, as well as geophysical surveys, the testing of production wells, the measuring of temperature, yield, and pH value on facilities, mineral water sampling, and the completion of chemical analyses.
The hydrogeological reconnaissance and the mapping of the terrain covered an area of about 100 km2. There were recorded 172 occurrences of groundwater and 10 occurrences of mineral water by the research whereby overall 45 water samples were taken from significant occurrences for the completion of chemical analyses. During the year 2001 the hydrogeological mapping of the terrain was carried out. It included visits to all occurrences and facilities, measuring of both quantities and temperatures of water, and taking samples for chemical analyses. Numerous geophysical surveys were carried out in the study area for various purposes [1]. Geoelectrical sounding was carried out on three profiles: Lapordinac-Ljiljance, Kraljeva
kuca-Levosoje and BoZinjevac-Trnovac on overall 25 measuring points. The aim of these surveys was to determine the position of granite and shale at the floor of Tertiary sediments and the separation of environments with various geological characteristics. In 1992 geophysical surveys were carried out determining the
presence of a young magmatic body in the floor of Tertiary sediments in the zone of Rakovac. Geophysical surveys were also carried out in the year 2002 by geo-electric sounding with 15 probes. They are related to the determination of the distribution of aquifers between the facilities: A-2 and A-4 (Fig. 3).
Monitoring of the regime of Bujanovac valley mineral waters was carried out continually in the period from 1981 to 1987 years, as well as control measurements in 1995. Monitoring of yield, temperature, and chemical composition was carried out during the years 2001 and 2002 (at the facilities of Partizanska Cesma, A-2, A-3, BH-2, BH-3 and testing of the A-4 well in 2007).
The exploration methodology is also based on hy-drochemical examinations of mineral waters of the Bujanovac valley carried out in the period from 1995 to 2010. The knowledge of macrocomponents and geochemistry of fluorine makes the basis of these explorations, the latter ranging from the most common ways of fluoride arrival to groundwater, to factors affecting the ion migration.
GEOLOGICAL SETTING
The terrain of the Bujanovac valley, as regards geological-tectonic setting belongs to Serbian crystalline core, the Serbian crystalline core (Fig. 2). This large tectonic unit spreads from Belgrade to south-western part of the Vranje valley-Presevo. It disappears to the north below Tertiary sediments of the south edge of the Pannonian basin, and in the south to Presevo below sediments and vulcanite in the form of the Strumica
I_I
Fig. 2. Detailed tectonic map of study area (according to [1])
(Legend: A — Serbo-Macedonian mass; Ai — westeren belt; A2 — Kitka area; A3 — monoclyne of Ko c ura; Bi — Vranje graben; B2 — Krivorek depression 1 — Pcinja basin; 2 — Vrtogos-Klenik fault; 3 — marginel faults of Vranje graben; 4 — Veternik-Lukovo fault; 5 — Tupal dislocation; 6 — Ljiljanska reka fault).
fault via Thessalonica and farther to the south. Terrains of the Serbian crystalline core represent a wreath mass between two geosynclines: the Carpathian- Balkan and the Dinarides. They are made of metamor-phite of high degree crystallinity with the rare occurrence of Mesozoic sediments. Crystalline complexes are metamorphosed, folded in Caledonian and Variscan orogenies with the intrusion of huge masses of granitoides. Alpine movements have included western margin part of the Serbian crystalline core. The terrains of the Serbian crystalline core are made of low metamorphosed Palaeozoic formations, Mesozoic sediments and sedimentary-volcanogenic formations with the occurrence of ultrabasite which does not occur in the Serbian crystalline core. Essential elements of the Serbian crystalline core setting were formed during Alpine movements. Tertiary sediments overlie older layers on both tectonic units. In the Cenozoic — Palaeogene longitudinal dislocations occurred, as well as the breaking into single blocks in the Serbian crystalline core whereby the intrusion of vulcanite along dislocation lines occurred, for example: Surdulica gra-nodiorite massif, Vlajna granodiorite, the Bujanovac granite massif. Since the Miocene large or small basins, having diagonal position in relation to old structures, have been formed in the Serbian crystalline
core. In this way the Bujanovac valley with the occurrence of intensive volcanic activity was formed as well.
During Caledonian and Variscan orogenies, the folding of crystalline shale occurred when the impression of the Bujanovac granite massif occurred there. Subsequently, ruptures were formed in this area, thus during the Eocene a basin was formed wherein molasse and turbidite sediments of the Upper Miocene were deposited. After the Upper Eocene there was land in this area. In the Middle Eocene it sank again. At the end of the Middle Miocene (about 12—11 million years) the whole area was taken by tectonic stress with the occurrence of several parallel deep dislocations, their strike being approximat
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