Hydrogeochemistry of Fluoride and Salinization Mechanism of Groundwater in the Singida Region, Central Tanzania
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Date
2009
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Abstract
This study focuses on the determination of factors that control high fluoride groundwater and salinization in
basement aquifers of a semi-arid area in central Tanzania. Water samples were collected from productive
dugouts, shallow wells and boreholes. The presence of 18O, 2
H, and major cation and anion chemistry, including
fluoride, was determined with the use of standard analytical techniques. A sodium-bicarbonate type of water
dominates the study area. The 18O - 2
H relationships suggest that the infiltration of water and groundwater has
undergone evaporation while in some cases preferential flow mechanisms are suggested. Shallow wells and
dugouts were found to have higher concentrations of both fluoride and chloride and this fact is partly attributed
to the effect of evapotranspiration. The main mechanism for fluoride input into groundwater as well as
salinization is attributed to the leaching of surface and near-surface soil salts, especially trona. No clear
relationship was observed between the depth of wells/boreholes and fluoride concentration. Similarly, there is
hardly any clear relationship between the fluoride concentration and the geomorphology of the study area. A
more detailed investigation is needed to determine the relationship between sampling depth, fluoride
concentration and salinization.
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Nkotagu, H.H., 2009. Hydrogeochemistry of fluoride and salinization mechanism of groundwater in the Singida region, central Tanzania. The Basement Aquifers of Southern Africa, p.80.