Seasonal analysis of heavy metaloids concentrations in water and sediments of selective Karu rivers, Nigeria: Ecological implications and risk assessment

There is currently no universally agreed-upon standard for acceptable levels of heavy metals in the surface water and sediment of selected Nigerian rivers. In the study, the concentrations of heavy metals were determined in the surface water and sediments of rivers located in Karu, Nasarawa state, Nigeria. An inductively coupled plasma mass spectrometer was employed to analyze both water and sediment samples. When both seasons are considered, the mean levels of zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd), lead (Pb), and arsenic (As) in water samples from the cold season are approximately two times higher than the mean values in the hot season. The mean values for the cold season were 0.238, 0.278, 0.272, 0.003, 0.075, and 0.082 mg/L for zinc, copper, iron, cadmium, lead, and arsenic, respectively. In sediment samples, the mean concentrations of Zn, Cu, Fe, Cd, Pb, and As in the cold season were 1.72, 0.57, 372.45, 0.80, 0.68, and 14.35 mg/kg, respectively. The geo-accumulation index (Igeo) and the potential ecological risk index (RI) indicated that the contamination levels of the river sediment were low. Nevertheless, a more comprehensive analysis of heavy metals in both water and sediment is required to fully evaluate the health of the ecosystem and effectively manage any potential risks. •Surface water was slightly acidic, with pH ranging from 6.3 to 6.5.•Electrical conductivity and TDS values remained within acceptable limits.•Heavy metal concentrations were higher in cold seasons for both water and sediment.•Sediment samples showed elevated iron and cadmium levels, posing ecological risks.•Cancer risk from arsenic in sediment exceeded safe levels, especially in children.