[A-HW22] 流域の物質輸送と栄養塩循環－源流域から沿岸海域まで－

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

*中屋 眞司¹、高田 遼吾¹、安元 純²、吉谷 純一¹、ルゴディシャ イノセント³、ルインボ ズベリ³、コマケッチ ハンス⁴、モレル トーマス⁵ (1.信州大学工学部水環境・土木工学科、2.琉球大学農学部地域農業工学科、3.ネルソンマンデラ科学技術大学、4.ネルソンマンデラ科学技術大学ワイズフューチャー、5.タンザニアさくら女子中学)

キーワード：フッ素、大地溝帯、タンザニア、メルー山流域

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.