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Assessment of Heavy Metal Pollution in a Trans-Boundary River: The Case of the Akagera River

F. Nshimiyimana, I. Nhapi, U. G. Wali, H. Nsengimana, N. Banadda, I. Nansubuga, F. Kansiime

Abstract


Lake Victoria one of the biggest fresh water lakes in the world is faced with serious water quality deterioration as a result of the activities of the riparian population and the uncontrolled pollution of its tributary rivers. The Akagera River drains Burundi, Rwanda, Tanzania and Uganda and is one of the major rivers discharging into Lake Victoria. Although the status of water quality in Lake Victoria has been studied, little is known about actual sources, especially the role of trans-boundary rivers. This study focused on quantifying and monitoring heavy metal levels mainly Cadmium, Chromium, Copper, Iron, Lead, Manganese, Zinc, and Conductivity, pH, Temperature, and Turbidity in the Akagera River. Sampling was conducted monthly from February, 2008 to March, 2009 based on eleven sampling points, four of which are on the tributary rivers, Nyabarongo, Akanyaru and Muvumba (origin Burundi). Cadmium, Chromium and Lead were analyzed using an Atomic Absorption Spectrometer. Copper, Iron, Manganese and Zinc were analyzed using a colorimeter, whilst conductivity, temperature, turbidity and pH were measured in the field using HACH field kits.

The results indicate that the levels of Copper and Lead in Akanyaru are higher than those in other rivers, while Muvumba River shows high concentration of Cadmium of about 0.965 mg/L. The mean values observed are 0.965 mg/L for Cadmium, 0.015 mg/L for Chromium, 0.045 mg/L for Lead, 0.415 mg/L for Copper, 0.553 mg/L of Zinc, 14.62 mg/L for Manganese and 0.56 mg/L for Iron. These parameters show that the river contains high values of Cadmium, Lead and Manganese, compared to the WHO Guidelines for Drinking Water Quality and Canadian Water Quality Guidelines for the protection of aquatic life. This presents serious problems to the aquatic life and to the different water users. The high levels in the river were attributed to agricultural, industrial and high erosion levels in the catchment. Since this is a trans-boundary river, it was recommended that the riparian countries come together and develop appropriate measures (including institutions) to identify and control the sources of pollution.


Keywords


Akagera River, heavy metals, land use activities, pollution, Transboundary River, water quality.

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