Bioaccumulation Factors (BAF) for Heavy Metals in Freshwater Fish, Water and Sediment of Some Aquatic Habitats in Sokoto State, Nigeria

Abstract

This study was conducted to determine and compare the Bioaccumulation Factors (BAF) for Heavy Metals in Fresh Fish, Water and Sediment of Some water bodies in Sokoto State, heavy metals contents of all the samples were found by atomic absorption spectrometry (AAS), Clarias gariepinus consistently exhibited the highest median BAFs for cadmium (Cd) and zinc (Zn), followed by Oreochromis niloticus. At the same time, Bagrus bayad showed the lowest accumulation for these metals. The elevated BAFs for Cd—particularly in C. gariepinus—are ecologically and toxicologically significant. The baseline assessment of heavy metal contamination across four aquatic systems in Sokoto State—Wurno River, Rima River, Romo Lake, and Shagari Dam—revealed distinct spatial and matrix-specific pollution profiles, with Shagari Dam emerging as a hotspot for Zn (0.387 mg/kg) and Mn (0.336 mg/kg) in sediment. At the same time, Rima River showed elevated levels of Cu (0.198 mg/kg) and Cd (0.070 mg/kg). Temporal analysis of Zn in water revealed pronounced seasonal fluctuations, particularly at Wurno River and Romo Lake, where concentrations peaked during months March, April, and October, potentially linked to agricultural runoff or industrial discharge cycles (Figure 2) and The high Mn concentrations in water, particularly at Wurno River and Romo Lake (exceeding WHO guidelines of 0.05–0.1 mg/L). Therefore, monitoring and managing these potential pollution sources is crucial to protecting the lake's ecosystem and the local population's health. The concentrations observed in the fish, particularly in B. bayad, are a clear indication that the dam's ecosystem is under stress from these pollutants.