Spatial Distribution and Pollution Assessment of Heavy Metals in the Sediments of River Gwagwalada

Abstract

Sediments serve as long-term sinks for heavy metals in river systems, reflecting the cumulative effects of natural and anthropogenic inputs. This study assessed the concentrations, spatial distribution, seasonal variation, and contamination status of seven heavy metals (Cd, Co, Cr, Fe, Mn, Ni, and Zn) in sediments from River Gwagwalada, Nigeria. Sediment samples were collected from twelve stations during the wet and dry seasons and analyzed using Atomic Absorption Spectrophotometry (AAS). Mean metal concentrations (mg/kg) were Cd (0.52), Co (17.46), Cr (11.43), Fe (1643.67), Mn (350.03), Ni (11.16), and Zn (23.26), with generally higher concentrations observed at downstream locations. Analysis of variance (ANOVA) revealed significant seasonal variations for Cd (p = 0.032), Fe (p < 0.001), and Ni (p = 0.002), whereas Co, Cr, Mn, and Zn showed no significant seasonal differences (p > 0.05). Contamination factor (CF) and pollution load index (PLI) were used to evaluate sediment quality. Cadmium exhibited moderate contamination (CF = 1.73), while the remaining metals showed low contamination levels (CF < 1). The overall PLI (0.25) indicated that the sediments were generally unpolluted. These findings provide baseline information for environmental monitoring and sustainable management of River Gwagwalada.