East African magadi (trona): fluoride concentration and mineralogical composition

Nielsen, Joan Maj

doi:10.1016/s0899-5362(99)00107-4

Cited by 32 publications

(24 citation statements)

References 9 publications

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“…The two most likely explanations for this observation are firstly that these waters do not remain in extended contact with the rock, and secondly that alteration products (such as paleosoils), while common in the lahars, are largely absent. No calcrete or lacustrine salty deposits with salty soils and scooped magadi (Nielsen, 1999) occur in this area. All these readily leachable products rather are found in the Uwiro graben and elsewhere in the lower lying and flatter land away from the volcano itself.…”

Section: Prospecting Strategymentioning

confidence: 91%

Prospecting for safe (low fluoride) groundwater in the Eastern African Rift: the Arumeru District (Northern Tanzania)

Ghiglieri

Balia

Oggiano

et al. 2010

Hydrol. Earth Syst. Sci.

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Abstract.A multidisciplinary research effort, including geological, hydrogeological, hydro-chemical, geophysical and hydrological investigations, was aimed at locating a source of safe groundwater for a district of northern Tanzania, within the western branch of the East Africa Rift Valley, where water shortage is common and much of the surface water carries unacceptable levels of dissolved fluoride. The 440 km 2 study area lies in the northern part of Arumeru district and is dominated by Mt. Meru (4565 m a.s.l.). The local climate is semi-arid, with distinct wet and dry seasons. Four hydrogeological complexes were identified, occurring within different volcanic formations, either alone or superimposed upon one another. The groundwater flow system was interpreted from the spatial distribution of the springs, combined with a lithology-and geometry-based reconstruction of the aquifers. The dominant pattern consists of a multi-directional flow from the higher elevations in the south towards the lower areas in the north, but this is complicated by structures such as grabens, faults, lava domes and tholoids. After the identification of the major fluoride source, an interference pattern between groundwater and high fluoride surface water was drawn. Finally, vertical electrical soundings were performed to define the location of aquifers in regions where release of fluoride was prevented. The methodological approach for the prospecting of safe water in a semi-arid, fluoride polluted region was validated by the drilling of a 60 m deep well capable of supplying at least 3.8 l/s of low fluoride, drinkable water.

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Section: Prospecting Strategymentioning

confidence: 91%

Prospecting for safe (low fluoride) groundwater in the Eastern African Rift: the Arumeru District (Northern Tanzania)

Ghiglieri

Balia

Oggiano

et al. 2010

Hydrol. Earth Syst. Sci.

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“…These phases can be directly precipitated from super-saturated solutions and frequently form, sometimes in conjunction with zeolites, crusts, hardpans and calcrete, as in the calcrete OLD9, in breccias (OLD3, 4 and 5) and in the crust of a lake deposit (2474 C). Trona is referred to locally as "scooped magadi" when it forms an efflorescent crust on the soil surface in association with mixtures of halite, quartz, villiaumite, kogarkoite and thermonatrite (Nielsen, 1999). This assemblage was not present in samples in which trona was associated with either natrite, sylvite, aphthitalite, goethite, phillipsite, chabazite and analcime of probably secondary formation (ENG8b), or calcite, cancrinite, phillipsite, chabazite and secondary analcime (2474 C).…”

Section: Mineralogymentioning

confidence: 99%

Hydrogeology and hydrogeochemistry of an alkaline volcanic area: the NE Mt. Meru slope (East African Rift – Northern Tanzania)

Ghiglieri

Pittalis

Cerri

et al. 2012

Hydrol. Earth Syst. Sci.

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Abstract. The objective of this study is to analyze the geochemical conditions associated with the presence of fluoride (F − ) in the groundwater of an area of Northern Tanzania. The studied aquifers are composed of volcanic rocks such as phonolitic and nephelinitic lavas, basalts, lahars of various ages and mantling ash. Sedimentary rocks consisting of fine-grained alluvial and lacustrine deposits occur as well. Samples collected from springs, borehole and surface water, during two monitoring surveys, were analyzed for the various physico-chemical and isotopic parameters. The geochemical composition of water is typically sodium bicarbonate. High values of F − (up to 68 mg l −1 ) were recorded. The highest values of fluoride agreed with the highest values of pH, sodium and bicarbonate. Dissolution of major ions, exchange processes and precipitation of Ca 2+ from supersaturated solutions joined with the local permeability and hydraulic gradients, control the fluoride mobilization and the contamination of the area.

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“…Ground salt also contains high content of fluoride, an issue not seen with ash filtrate, which can lead to exceed the daily consumption limit (Mabelya et al 1997;Nielsen 1999;Nielsen & Dahi 2002;Kaseva 2006). Given its potentially numerous negative effects, these results support previous findings which suggest ground salt should not be used as a cooking additive.…”

Section: Discussionsupporting

confidence: 85%

“…There are several sources proximate to Northern Uganda capable of producing ground salt; Lake Magadi, Kenya; Lake Katwe, Uganda; Lake Natron, Tanzania; and El-Atrun, Sudan (Nielsen 1999;Nielsen & Dahi 2002). Collectively, this ground salt is referred to as 'magadi' in eastern Africa, a salt which is usually scooped from the topmost layer of earth and which can also contain a mixture of other elements and soil (Nielsen 1999). Aside from personal use, ground salt is also transported to various town markets for sale by volume.…”

Section: History and Importance Of Indigenous Salt Use In Rural Ugandamentioning

confidence: 99%

Use of filtrate from crop residue ash for cooking in rural households in Northern Uganda.

Bergeson¹

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East African magadi (trona): fluoride concentration and mineralogical composition

Cited by 32 publications

References 9 publications

Prospecting for safe (low fluoride) groundwater in the Eastern African Rift: the Arumeru District (Northern Tanzania)

Prospecting for safe (low fluoride) groundwater in the Eastern African Rift: the Arumeru District (Northern Tanzania)

Hydrogeology and hydrogeochemistry of an alkaline volcanic area: the NE Mt. Meru slope (East African Rift – Northern Tanzania)

Use of filtrate from crop residue ash for cooking in rural households in Northern Uganda.

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