Stream sediments geochemical and heavy metal pollution assessment of Irese, Igoba and Ilado areas (north of Akure), Southwestern Nigeria

Abstract

<title>Abstract</title> This study examines geochemical characteristics and heavymetal pollution of stream sediments and rocks in Irese, Igoba and Ilado, where no prior assessment exists. Thirty streamsediment samples were systematically collected (1 sample per 4 km², 1 m depth), along with six petrographic and twenty ICPMSanalyzed rock samples. Grapher, Surfer, SPSS and Excel facilitated evaluation of enrichment levels, pollution indices and multivariate relationships. Elevated Fe, Al, Pb, Zn, and Cu concentrations at several sites suggest derivation from mafictointermediate source rocks and potential sulphide mineralization under hydrothermal influence. Univariate statistics show negative skewness for Cu, Zn, Cd, Ba and positive skewness for Fe, Pb, Ni, Co, Mn, Cr, indicating multimodal distributions and diverse provenance. Factor analysis yielded three components: (1) CuPbZn linked to sulphide mineralization, (2) polymetallic pathfinder assemblages, and (3) weathered elements reflecting prolonged alteration. Hierarchical clustering grouped elements into aluminosilicate/siderophile (FeAl), sulphide-related (CuPbZnCd) and lithophile (NiCoMnCr) clusters, underscoring varied source contributions, including felsic and mafic rocks. Correlation patterns corroborate mixed sediment origins. Index of Geoaccumulation values show unpolluted conditions for most metals, moderate Pb pollution likely from anthropogenic activities, and localized Fe enrichment. Enrichment Factors indicate minimal enrichment for most elements, whereas Pb and Zn display moderatetosignificant enrichment, highlighting prospective lead-zinc sulphide mineralization zones in the area. The study provided a baseline geochemical dataset crucial for future environmental monitoring, landuse planning, guiding mineral exploration, and resource development strategies.