[A-HW22] Materials transport and nutrient cycles in watersheds; from headwaters to coastal seas

[AHW22-19] Water Source Zones and Hydrochemical Properties of Fluoride Water in Mt. Meru Watershed, Tanzania

*Shinji Nakaya¹, Ryogo Takada¹, Jun Yasumoto², Junichi Yoshitani¹, Innocent Lugodisha³, Zuberi Dominicus Lwimbo³, Hans Komakech⁴, Thomas Reuben Mollel⁵ (1.Department of Water Environment and Civil Engineering, Faculty of Engineering, Shinshu University, Japan, 2.Department of Regional Agriculture Engineering, University of the Rykuyus, Japan, 3.School of Materials, Energy, Water and Environmental Sciences, NM-AIST, Tanzania, 4.WISE-Future, NM-AIST, Tanzania, 5.SGSS and Institute of resources assessment-UDSM, Tanzania)

Keywords:Fluoride, Great Lift Valley, Tanzania, Mt. Meru watershed

Fluoride is leaching to natural water system from volcanic rocks and ashes with alkali volcanic activity along Great Lift Valley in east Africa. Tanzanian people in Great Lift Valley are also suffering drinking water including high fluoride ( > 1.5 mgF/L of WHO) and water shortage. We investigated the groundwater and river water fluoride pollutions in area between Arusha of Mt. Meru watershed and Moshi of Mt. Kilimanjaro watershed in September, 2018 to provide the solutions to these issues as No. 6 of SDGs. We find some results below:

1. Average fluoride content is 4.0 mgF/L in Mt. Meru watershed, and 0.5 mgF/L in Mt. Kilimanjaro watershed.

2. Fluoride concentrates in Na-HCO₃ type water, and Fluoride tend to increase with Na and pH.

3. Groundwater fluoride tends to be increasing with residence time, but in recent twenty five years, fluoride is
higher in younger groundwater.
4. Well waters supplied to Arusha city come from the recharge zone of 2,000 m to 3,000 m in altitude
of Mt. Meru, and the fluoride content tend to increase with the recharge altitude.