Abstract:

This study assessed the hydrogeochemical characteristics, heavy metal bioaccumulation in fish and aquatic species, and associated public health risks in River Benue, Nigeria. Water samples and aquatic species including fish, shrimp, crab and molluscs were analysed for physicochemical parameters and ten heavy metals: Pb, Cd, Cr, Hg, As, Ni, Cu, Zn, Fe and Mn using standard analytical procedures and Atomic Absorption Spectrophotometry. The results revealed spatial variations in water quality, with downstream locations exhibiting elevated turbidity (8.63 ± 0.84 NTU), biological oxygen demand (4.74 ± 0.49 mg/L), and chemical oxygen demand (14.02 ± 1.53 mg/L). Heavy metal concentrations in downstream water samples exceeded World Health Organization limits for Pb (0.024 ± 0.003 mg/L), Cd (0.007 ± 0.001 mg/L), Cr (0.068 ± 0.007 mg/L), As (0.014 ± 0.002 mg/L), Ni (0.031 ± 0.004 mg/L), Fe (0.71 ± 0.09 mg/L), and Mn (0.18 ± 0.03 mg/L). Bioaccumulation analysis showed higher metal accumulation in molluscs and crabs, with Pb ranging from 0.39 ± 0.05 to 0.61 ± 0.08 mg/kg and Cr ranging from 0.44 ± 0.06 to 0.71 ± 0.09 mg/kg. Public health risk assessment indicated Hazard Quotient values for Pb ranging from 1.21 to 1.84 and Hazard Index values ranging from 1.98 to 3.12, exceeding the acceptable safety threshold. The study concludes that River Benue is under increasing hydrogeochemical and anthropogenic contamination with significant implications for aquatic ecosystem sustainability, food safety and public health.