Abstract
Siloam’s groundwater is reportedly characterized by high fluoride. In response to the reported high incidence of dental fluorosis in the area, sources of elevated fluoride in the groundwater were investigated. Total fluoride (TF) was determined using Ion Chromatograph and Fluoride Ion Selective Electrode. The mineral composition of rocks and soils were determined using X-ray Fluorescence and X-ray diffraction, respectively. Results revealed that groundwater fluoride concentration ranged from 3.92 to 4.95 mg/L. Na-Cl water type was found to be dominant in the water samples. TF content of the rocks and soils ranged from 10 to 2000 mg/L. Leachates were obtained by making a slurry from the samples at a predetermined temperature and time. TF in leachates ranged between 0.27 and 14.88 mg/L and 0.05 to 10.40 mg/L at induced, and non-induced temperatures, respectively. The possible source of fluoride has been previously inferred to be caused by fluorite minerals occurring at greater depth. However, this study proves that fluoride decreases with depth and the elevated fluoride in the groundwater is caused by smectite-kaolinite clay, muscovite and chlorite minerals abundant in the area. Geothermal temperature exhibited by the groundwater in the area is a major factor enhancing the release of fluoride from the clay materials.
Highlights
Water is an important basic resource necessary for human development and economic growth
One soil and rock samples were collected from the surface in the study area while twelve borehole cuttings from the subsurface were sampled for analysis
Fluoride levels exceeding 1.5 mg/L recommended by the WHO was determined in the groundwater of the study area
Summary
Water is an important basic resource necessary for human development and economic growth. The supply of clean and safe water over the last decade has improved progressively globally[1] Despite this recorded success, millions of people are not connected to water supply infrastructure and often resort to several alternative sources for their domestic water n eeds[2,3]. Amongst which are the presence of elevated levels of arsenic, lead, cadmium, mercury, fluoride, nutrients and microorganisms[9,10,11]. Some of these contaminants are more linked to geogenic sources than others. The consumption of fluoride rich water has been linked to various public health burden notable among which are dental and skeletal fluorosis[12,13,14]. Occurrence of elevated fluoride in groundwater is an emerging world-wide threat that affects over 200 million people worldwide and over 80 million people in East A frica[21]
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