Heavy Metal Concentrations and Spatial Variation in Fish, Water, and Sediments of River Niger: A Comparative Analysis

Abstract

There are many persistent heavy metals released into our environment, among which are heavy metals. This study was conducted to determine the concentrations of selected heavy metals—cobalt (Co), manganese (Mn), iron (Fe), and silver (Ag)—in fish, water, and sediment samples collected from three sites along the River Niger: Atani, Bridgehead, and Otuocha. The concentrations were measured using atomic absorption spectrophotometry (AAS 240FS). Results revealed site-specific variations in heavy metal accumulation across sample types. The highest concentrations of Co (0.665 ± 0.018 mg/L), Mn (13.780 ± 3.507 mg/L), and Fe (48.77 ± 0.382 mg/L) in water were found at the Otuocha site. Similarly, Otuocha recorded the highest levels of these metals in both fish and sediment samples. Iron (Fe) concentration in Otuocha fish tissue reached 47.12 ± 0.785 mg/kg, indicating significant bioaccumulation. In contrast, manganese was completely absent in the water, sediment, and fish samples from Bridgehead.Silver (Ag) exhibited a different trend, with the highest concentrations consistently observed in all sample types from the Bridgehead site: 0.729 ± 0.001 mg/kg in fish, 0.781 ± 0.036 mg/L in water, and 0.668 ± 0.044 mg/kg in sediment. This study demonstrates significant site-specific variations in heavy metal distribution within the River Niger ecosystem. The elevated concentrations of cobalt, manganese, iron, and silver—particularly the high Fe levels in fish tissue at Otuocha and Ag enrichment at Bridgehead—indicate localized contamination sources and potential ecological risks. These findings emphasize the urgent need for continuous monitoring, effective pollution control, and sustainable management strategies to safeguard aquatic biodiversity and public health.