Assessment of Heavy Metal Contamination in Water, Sediment, and Fish Tissues from Biu Reservoir, Borno State, Nigeria

Abstract

Heavy metals are naturally occurring elements with high atomic weights and densities at least five times greater than water. Known for their toxicity, persistence, and bioaccumulation, they pose serious risks to aquatic ecosystems and human health. This study evaluated the contamination levels of six heavy metals; zinc (Zn), lead (Pb), cadmium (Cd), copper (Cu), manganese (Mn), and chromium (Cr); in water, sediment, and two fish species (Oreochromis niloticus and Clarias gariepinus) from Biu Reservoir, an important freshwater source in southern Borno, Nigeria. Using Atomic Absorption Spectrophotometry, results showed Clarias gariepinus accumulated more metals, particularly in gills. Lead in water (0.016 mg/L) and cadmium in O. niloticus gills (0.058 mg/kg) exceeded WHO safety limits. While other metals remained within permissible ranges, the elevated Pb and Cd levels pose potential health risks. Continuous environmental monitoring and pollution control are recommended.