Assessment of Heavy Metals in Water from Lake Kivu, Rwanda

Heavy metals are among the pollutants that threaten living organisms including human beings. Heavy metals in water are of great concern due to their toxicity and ability to bio-accumulate in aquatic organisms. There is a need to regularly monitor their concentration in an aquatic medium. The present study was conducted to evaluate the level of heavy metals in lake Kivu. Water samples from lake Kivu were taken from three sites, namely: Rusizi, Karongi, and Rubavu. Heavy metals were analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Copper, lead, cadmium, chromium, manganese, mercury, and arsenic were analyzed in the water samples. The concentration of copper ranged from 3.240 to 10.011 µg/L, the concentration of lead varied from 8.81 to 37.44 µg/L, cadmium ranged from 5.014 to 14.012 µg/L. Chromium concentration was between 139.5 and 226.6 µg/L, and that of manganese was between 598.3 and 795.7 µg/L, mercury concentration ranged from 0 to 0.047 µg/L while Arsenic was not detected. Thus, except for arsenic, the concentrations of heavy metals in Kivu lake waters were above the Environmental Protection Agency (EPA) maximum permissible limit for class III surface water intended for fish consumption, recreation, propagation, and maintenance of a healthy population of fish and wildlife. There is a need to further establish the sources of lake water pollution and limit the amounts of heavy metals entering lake Kivu to avoid the excess heavy metals beyond the maximum tolerable limit.