Seasonal water chemistry variability in the Pangani River basin, Tanzania
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Date
2017-09-17Author
Selemani, Juma
Zhang, Jing
Muzuka, Alfred
Njau, Karoli
Zhang, Guosen
Maggid, Arafa
Mzuza, Maureen
Jin, Jie
Pradhan, Sonali
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Show full item recordAbstract
The stable isotopes of δ18O, δ2H, and 87Sr/86Sr and
dissolved major ions were used to assess spatial and seasonal
water chemistry variability, chemical weathering, and hydrological
cycle in the Pangani River Basin (PRB), Tanzania.
Water in PRB was NaHCO3 type dominated by carbonate
weathering with moderate total dissolved solids. Major ions
varied greatly, increasing from upstream to downstream. In
some stations, content of fluoride and sodium was higher than
the recommended drinking water standards. Natural and anthropogenic
factors contributed to the lowering rate of
chemical weathering; the rate was lower than most of tropical
rivers. The rate of weathering was higher in Precambrian than
volcanic rocks. 87Sr/86Sr was lower than global average
whereas concentration of strontium was higher than global
average with mean annual flux of 0.13 × 106 mol year−1.
Evaporation and altitude effects have caused enrichment of
δ18O and δ2H in dry season and downstream of the river.
Higher d-excess value than global average suggests that most
of the stations were supplied by recycled moisture. Rainfall and groundwater were the major sources of surface flowing
water in PRB; nevertheless, glacier from Mt. Kilimanjaro has
insignificant contribution to the surface water.We recommend
measures to be taken to reduce the level of fluoride and sodium
before domestic use.