Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study

Olaka, Lydia; Wilke, Franziska; Olago, Daniel; Odada, Eric O.; Mulch, Andreas; Musolff, Andreas

doi:10.1016/j.scitotenv.2015.11.161

Cited by 106 publications

(46 citation statements)

References 40 publications

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“…(Figure 9a) shows negative correlation with groundwater, indicating the water with lighter isotope had experienced longer water-rock interactions. It has been reported that isotope-depleted water contains a high-fluoride concentration [19,67]. The δ 18 O versus fluoride diagram (Figure 9a) show that there is a significant isotopic contrast between the shallow groundwater and deep groundwater.…”

Section: Genesis Of High Fluoride Groundwatermentioning

confidence: 82%

“…The occurrence of health problems related to fluoride are well documented in the Central Ethiopian rift valley, whereas hydrogeochemistry and F − enrichment mechanism in the southern Ethiopian rift valley have not yet been investigated and are poorly understood.Fluoride in groundwater is related to various rock types, that is, sedimentary rocks [13,14], igneous rock [12,15], or metamorphic rock [16,17], influenced by geochemical and climatological conditions [18]. Volcanic emissions and geothermal water are also sources of fluoride in groundwater [19][20][21]. Fluorine-bearing minerals like topaz, fluorite, tourmaline, muscovite, biotite, hornblende and villianmite, release F − through weathering and water-rock interaction [22][23][24].…”

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confidence: 99%

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Geochemical Evolution of Fluoride and Implication for F− Enrichment in Groundwater: Example from the Bilate River Basin of Southern Main Ethiopian Rift

Haji

Wang

et al. 2018

Water

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Groundwater is the most important source of drinking water. Fluoride was found in high concentrations in the groundwater from deep wells of the water supply in the southern main Ethiopian rift. The high concentration of fluoride is dominantly geogenic rather than anthropogenic in origin, as the agricultural area was not found to be contaminated with NO 3 − . Knowledge of fluoride enrichment will help to provide management plans for developing deep groundwater and minimizing the health risks of exposure to fluoride. The chemical processes of fluoride were investigated in the waters in the Bilate River basin using hydrochemical and isotopic tools. The F − concentration ranged from 0.5 to 1.29 mg/L in water from shallow wells and from 0.48 to 5.61 mg/L in water from deep wells. Seventy percent of deep well samples had F − > 1.5 mg/L higher than the World Health Organization potable guideline. The high fluoride concentration in the groundwater was mainly situated in the rift valley of the Bilate River basin, in contrast with low F − groundwater in the highland. The concentration of fluoride was lowest in Ca-Mg-HCO 3 type groundwater and highest in Na-HCO 3 type groundwater. Moreover, F − was positively correlated with HCO 3 − , Na + , Na + /Ca 2+ and pH in groundwater and Na + /Ca 2+ ratios were increased along the flow path. Hydrogeological, hydrodynamic and hydrochemical conditions are responsible for fluoride accumulation in the deep aquifers. Strong dynamic flow in highland areas flush away weathered chemical components (e.g., F − ). Thus, surficial weathering is not a major controlling factor for high concentrations of Fluoride in deep groundwater but the combination of silicate hydrolysis and ion exchange mainly control fluoride enrichment in stagnant flow environments.In past decades, researchers have studied the geographical distribution of fluoride concentration [6-8] and its relationship with dental caries, dental fluorosis and skeletal fluorosis [9][10][11] in the Ethiopian rift valley. Water quality and fluoride sources were investigated in the central Ethiopian rift [12]. The occurrence of health problems related to fluoride are well documented in the Central Ethiopian rift valley, whereas hydrogeochemistry and F − enrichment mechanism in the southern Ethiopian rift valley have not yet been investigated and are poorly understood.Fluoride in groundwater is related to various rock types, that is, sedimentary rocks [13,14], igneous rock [12,15], or metamorphic rock [16,17], influenced by geochemical and climatological conditions [18]. Volcanic emissions and geothermal water are also sources of fluoride in groundwater [19][20][21]. Fluorine-bearing minerals like topaz, fluorite, tourmaline, muscovite, biotite, hornblende and villianmite, release F − through weathering and water-rock interaction [22][23][24]. Besides natural sources, fluoride can be derived from anthropogenic activity including mining activities, industrial emissions and agricultural fertilizers [25][26][27].The south Ethiopian rift is locate...

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Section: Genesis Of High Fluoride Groundwatermentioning

confidence: 82%

mentioning

confidence: 99%

Geochemical Evolution of Fluoride and Implication for F− Enrichment in Groundwater: Example from the Bilate River Basin of Southern Main Ethiopian Rift

Haji

Wang

et al. 2018

Water

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“…High F groundwater is commonly found associated with volcanic deposits (e.g. Olaka et al 2016); high As groundwater is commonly associated with sedimentary aquifers as well as mineralised basement settings, and elevated concentrations have been found in mining areas (Smedley 1996). Naturally occurring high salinity/brackish groundwater sources are also found within some arid and coastal settings (e.g.…”

Section: Resultsmentioning

confidence: 99%

Urban groundwater quality in sub-Saharan Africa: current status and implications for water security and public health

et al. 2017

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Groundwater resources are important sources of drinking water in Africa, and they are hugely important in sustaining urban livelihoods and supporting a diverse range of commercial and agricultural activities. Groundwater has an important role in improving health in sub-Saharan Africa (SSA). An estimated 250 million people (40% of the total) live in urban centres across SSA. SSA has experienced a rapid expansion in urban populations since the 1950s, with increased population densities as well as expanding geographical coverage. Estimates suggest that the urban population in SSA will double between 2000 and 2030. The quality status of shallow urban groundwater resources is often very poor due to inadequate waste management and source protection, and poses a significant health risk to users, while deeper borehole sources often provide an important source of good quality drinking water. Given the growth in future demand from this finite resource, as well as potential changes in future climate in this region, a detailed understanding of both water quantity and quality is required to use this resource sustainably. This paper provides a comprehensive assessment of the water quality status, both microbial and chemical, of urban groundwater in SSA across a range of hydrogeological terrains and different groundwater point types. Lower storage basement terrains, which underlie a significant proportion of urban centres in SSA, are particularly vulnerable to contamination. The relationship between mean nitrate concentration and intrinsic aquifer pollution risk is assessed for urban centres across SSA. Current knowledge gaps are identified and future research needs highlighted.

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“…Groundwater isotope compositions have been applied to evaluate processes and identify recharge sources in many tropical aquifers (Adomako et al, , ; Ayenew et al, ; De Vries et al, ; Fantong et al, , ; Faye et al, ; Gibrilla et al, ; Joshi et al, ; Kamtchueng et al, ; Mukherjee et al, ; Njitchoua et al, , ; Olaka et al, ; Sánchez‐Murillo et al, ; Shamsuddin et al, ; Taylor & Howard, ; Yeh & Lee, ). Evidence is mounting in support of the following hypothesis: that high‐intensity rainfall contributes disproportionately to recharge—that is, recharge ratios of intensive rainfall exceed recharge ratios of less intensive rainfall.…”

Section: Threshold Rainfall Intensities For Rechargementioning

confidence: 99%

Global Isotope Hydrogeology―Review

Jasechko

2019

Reviews of Geophysics

218

124

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Groundwater 18O/16O, 2H/1H, 13C/12C, 3H, and 14C data can help quantify molecular movements and chemical reactions governing groundwater recharge, quality, storage, flow, and discharge. Here, commonly applied approaches to isotopic data analysis are reviewed, involving groundwater recharge seasonality, recharge elevations, groundwater ages, paleoclimate conditions, and groundwater discharge. Reviewed works confirm and quantify long held tenets: (i) that recharge derives disproportionately from wet season and winter precipitation; (ii) that modern groundwaters comprise little global groundwater; (iii) that “fossil” (>12,000‐year‐old) groundwaters dominate global aquifer storage; (iv) that fossil groundwaters capture late‐Pleistocene climate conditions; (v) that surface‐borne contaminants are more common in younger groundwaters; and (vi) that groundwater discharges generate substantial streamflow. Groundwater isotope data are disproportionately common to midlatitudes and sedimentary basins equipped for irrigated agriculture, but less plentiful across high latitudes, hyperarid deserts, and equatorial rainforests. Some of these underexplored aquifer systems may be suitable targets for future field testing.

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Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study

Cited by 106 publications

References 40 publications

Geochemical Evolution of Fluoride and Implication for F− Enrichment in Groundwater: Example from the Bilate River Basin of Southern Main Ethiopian Rift

Geochemical Evolution of Fluoride and Implication for F− Enrichment in Groundwater: Example from the Bilate River Basin of Southern Main Ethiopian Rift

Urban groundwater quality in sub-Saharan Africa: current status and implications for water security and public health

Global Isotope Hydrogeology―Review

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