Identification of low fluoride areas using conceptual groundwater flow model and hydrogeochemical system analysis in the aquifer system on the flanks of an active volcano: Mount Meru, Northern Tanzania

George Bennett, Jill Van Reybrouck, Ceven Shemsanga, Mary Kisaka, Ines Tomašek, Karen Fontijn, Matthieu Kervyn, Kristine Walraevens

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Abstract

This study investigates the localities of low and high F groundwaters in the aquifer system on the flanks of Mount Meru to come up with guidelines to provide groundwater that can be used for drinking water supply without health impacts on the population. Our study focuses on parts of the flanks which were only partially or not at all covered by previous research. Results show that the groundwater chemistry of F-rich NaHCO3 alkaline groundwater in the area is controlled by dissolution of weathering aluminosilicate minerals, dissolution of F-bearing minerals, the precipitation of carbonate minerals as secondary products and the dissolution of magmatic gases. The low F groundwaters which can be used for drinking water supply without health impacts under the WHO limit (1.5 mg/L) are the low-fluoride springs from the high altitude recharge areas on the eastern and north-western flanks of Mount Meru inside Arusha National Park, whereas on the western flank the groundwater meets the Tanzanian limit (4.0 mg/L). On the south-western flank, the shallow aquifer composed of alluvium deposits at lower elevations, shows F values that meet the Tanzanian limit. One of the three investigated deep boreholes on this flank also meets the Tanzanian limit, suggesting a possibility of finding relatively low F groundwaters in the deep aquifer. Yet, in general, the deposits at lower elevations are found to contain high to very high F values, whereas the deposits at high elevations contain groundwater of low F values. Thus, the internal texture and grain size of geological formations, the burial depth of these formations and the water residence times are the factors determining the groundwater mineralisation and F concentrations in the area. The study identified that the deep hydrothermal system has influence on the high F groundwaters on the eastern and north-eastern flanks of Mount Meru.

Original languageEnglish
Article number152682
Number of pages17
JournalScience of the Total Environment
Volume814
DOIs
Publication statusPublished - 25 Mar 2022

Bibliographical note

Funding Information:
The authors thank the Tanzania Commission for Science and Technology (COSTECH) and Tanzania National Parks Authority (TANAPA) for providing research permits. Also, the authors thank Laura Segers and Stefanie Rombaut for their assistance during fieldworks. Thanks to Martine Leermakers and Natacha Brion (AMGC, Vrije Universiteit Brussel) for their help with chemical analysis of some water samples. Ines Tomašek acknowledges the support received from the VUB Strategic Research Program (SRP) and the Agence Nationale de la Recherche of the French government through the program “Investissements d'Avenir” (16-IDEX-0001 CAP 20-25). Karen Fontijn acknowledges support from F.R.S.-FNRS MIS grant F.4515.20. We also thank the two anonymous reviewers for their thoughtful comments that greatly improved this manuscript. Findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of VLIR-UOS. This research was funded by the Flemish Interuniversity Council - University Development Cooperation (VLIR-UOS) in the framework of project TZ2017TEA450A105 ‘Optimizing the valorization of water and rock resources for improved livelihoods in the Arusha volcanic region’.

Funding Information:
The authors thank the Tanzania Commission for Science and Technology (COSTECH) and Tanzania National Parks Authority (TANAPA) for providing research permits. Also, the authors thank Laura Segers and Stefanie Rombaut for their assistance during fieldworks. Thanks to Martine Leermakers and Natacha Brion (AMGC, Vrije Universiteit Brussel) for their help with chemical analysis of some water samples. Ines Tomašek acknowledges the support received from the VUB Strategic Research Program (SRP) and the Agence Nationale de la Recherche of the French government through the program “Investissements d'Avenir” (16-IDEX-0001 CAP 20-25). Karen Fontijn acknowledges support from F.R.S.-FNRS MIS grant F.4515.20 . We also thank the two anonymous reviewers for their thoughtful comments that greatly improved this manuscript. Findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of VLIR-UOS.

Funding Information:
This research was funded by the Flemish Interuniversity Council - University Development Cooperation (VLIR-UOS) in the framework of project TZ2017TEA450A105 ‘Optimizing the valorization of water and rock resources for improved livelihoods in the Arusha volcanic region’.

Publisher Copyright:
© 2021 Elsevier B.V.

Copyright:
Copyright 2022 Elsevier B.V., All rights reserved.

Keywords

  • Alkaline groundwater
  • East African Rift System
  • Hydrogeochemistry
  • Magmatic degassing

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