Abstract
Consumption of high fluoride in groundwater of Langtang area, manifest in the inhabitants of the area in form of dental fluorosis and skeletal fluorosis in older group. The aim of this study was to appraise the hydrogeochemistry of fluoride in the groundwaters of Langtang area. Thirty seven surface and groundwater samples and nine rock samples were collected in Langtang area for geochemical analysis. The Inductively Coupled Plasma Emission Spectrometry (ICPOES) was used to detect cations. The anions (Cl - , SO 4 = and Br - ) were determine by Ion Chromatography method. Fluoride was determined by the Specific Ion Electrode and bicarbonate was determined by titration. Major oxides, trace elements and rare earth elements for the rock samples were determined by the XRF method and fluorine by the Fusion method. Polished thin sections for rocks were prepared and studied. Geochemical results from analysis of the samples (rock and water) show that four major rock units make up the geology of the area; coarse porphyritic biotite granite, migmatite, rhyolite and riebeckite granites, the minor ones are pegmatite, trachyte, aplite and fine to medium grained biotite granites. The rhyolite, the riebeckite granites and trachyte have the highest level of fluorine content in the area (1,470, 1000, 900 and 800 ppm) respectively. The fluorine mineral (Fluorite) crystallized in the late stage of the magma as replacement of Fe/Mg mineral probably hornblende or biotite. Fluorine is leached into the groundwater from the rhyolite under the slightly alkaline (Ca-Mg-HCO 3 evolving Na-HCO 3 ) water in the area. The two major groundwater types (Ca-Mg-HCO 3 and Na-HCO 3 ) in the area have good relationship with content of fluoride in water. Although, the riebeckite granites have high fluorine content, contribution of fluoride from them is towards the southern portion of the map, owing to the groundwater flow direction. The different water sources in the area do not show variation in content of fluoride in water. However, groundwater barriers (dykes) may be responsible for some area having low fluoride (<1.5 mg/l) content. The consumption of high content of fluoride in the area has resulted in severe dental fluorosis in both children and youths and bowing of legs ( Genu Valgum ) in children with no discrimination between the sexes. Keywords: Fluoride, Fluorite, Fluorine, Fluorosis, Riebeckite Granite, Groundwater
Highlights
IntroductionIn most rural communities in northern Nigeria, the supply of water for drinking and other purposes is solely from surface (ponds, streams and rivers) and groundwater
In most rural communities in northern Nigeria, the supply of water for drinking and other purposes is solely from surface and groundwater
Study on the geochemical appraisal of fluoride in the waters of langtang area show that, among the rocks of the study area, the rhyolites have the highest content of fluorine followed by the riebeckite granites and trachyte respectively (1,470, 1000, 800 and 900 ppm)
Summary
In most rural communities in northern Nigeria, the supply of water for drinking and other purposes is solely from surface (ponds, streams and rivers) and groundwater. Fluoride enters the human body mainly through drinking water (Dissanayake, 1991). Sources of fluoride in ground water are fluoride bearing minerals from rocks, such as fluorite, Fluor-apatite, cryolite, hydroxylapatite, biotite, hornblende among others. Where biotite and amphiboles are abundant as in granites major sources of fluoride in water bodies is formed. In sedimentary rocks apatite may be an accessory mineral contributing fluoride to water while fluorite may be cementing materials in sandstones. U. DIbal, Department of Geology, University of Jos, Jos, Nigeria. K. Schoeneich, Department of Geology, Ahmadu Bello University Zaria, Zaria, Nigeria. I. Garba, Department of Geology, Ahmadu Bello University Zaria, Zaria, Nigeria.
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