Distribution and accumulation of trace metals in cultivated Lithomorphic Vertisols of Kaele Far North Cameroon

Abstract

Lithomorphic Vertisols of Kaélé (Far North Cameroon) are intensively cultivated during the dry season for onion and sorghum production. This study aimed to assess the distribution patterns and controlling factors of trace metal elements (TME) in cultivated Vertisol profiles developed on granite and gneiss. Four soil profiles were described according to the World Reference Base (WRB, 2022), and samples were collected from each master horizon (A–B–C) for physicochemical and geochemical analyses. The soils are clayey to sandy clay loam, moderately to strongly alkaline (pH 6.75–9.70), with moderate to high cation exchange capacity (14.40–39.84 cmol kg⁻¹). Trace metal concentrations followed the order: Ba > Sr > Zn > Cu > Cr > Ni > Pb > Cd. Barium exhibited the highest concentrations (30.42–426.87 mg kg⁻¹). Pearson correlation analysis revealed strong positive relationships between Ba and Ni (r = 0.95), Ba and Cu (r = 0.87), and Ba and Cr (r = 0.85), suggesting similar geochemical behavior. Principal Component Analysis (PCA) indicated that trace metal distribution is mainly controlled by parent material and soil physicochemical properties (clay content, CEC, pH). The results suggest that lithology and soil characteristics play a major role in controlling trace metal distribution in these Vertisols, while anthropogenic influence appears limited. These findings provide baseline data for sustainable soil management in the Sudano-Sahelian region.