Investigation of Heavy Metal Distribution and Radiation Levels in Sediments of the Benue River System

River sediments serve as important archives of both geogenic and anthropogenic contaminants, integrating inputs from watershed erosion, industrial discharge, and atmospheric deposition. This study investigates the co-distribution of heavy metal concentrations and naturally occurring radioactivity in bottom sediments of the Benue River system across five sampling transects spanning Taraba, Benue, and Kogi States, North East and North Central Nigeria. Sediment cores of 30 cm depth were collected at each transect and sectioned into 5 cm layers for depth-profile analysis. Heavy metal concentrations of cadmium, chromium, copper, lead, nickel, and zinc were determined by atomic absorption spectrometry after acid digestion. Radionuclide activity concentrations of radium-226, thorium-232, potassium-40, and cesium-137 were measured by high-purity germanium gamma spectrometry. Enrichment factor and geo-accumulation index were calculated for each heavy metal relative to local geochemical background values. Cluster analysis and principal component analysis were applied to identify common source signatures among measured parameters. Results indicate significant heavy metal enrichment near Makurdi urban center attributable to industrial and domestic waste discharges, with lead enrichment factors reaching 4.8. Cesium-137 was detected at low levels in all surface samples, confirming global fallout as a background source. Positive correlations between thorium-232 and chromium concentrations suggest co-transport from weathering of basement complex rocks. The study provides the first combined heavy metal-radionuclide sediment characterization dataset for the Benue River and identifies pollution priority zones for remediation. Keywords: heavy metals, sediment, radioactivity, Benue River, geo-accumulation