Geochemical Speciation and Principal Component Analysis of Toxic Metals in River Ogun Coastal Sediments, Southwestern Nigeria

This study investigated the influence and interactions of geochemical fractions of toxic metals in sediments of River Ogun in Nigeria. Fe, Mn, Zn, Pb, Cr, and Co were significantly present across the area, while Cu, Ni, and Cd were negligible. All the metals, except Zn, were found highly above their permissible limits in sediments. The bulk metal concentrations followed the trend: Fe >> Mn > Zn > Pb > Co >> Cu ? Cr ?Ni >> Cd. At p = 0.05, the concentrations (ppm) of Ni, Zn, Co, Mn, Fe, Pb, Cr, Cd, and Cu in the F1 were 1.72–5.84, 13.2–15.0, 1.16–3.41, 56.1–77.2, 198–212, 9.32–14.3, 1.96–3.66, 0.55–1.61, and 0.56–1.98, respectively, while the values were 12.1–13.6, 113–270, 67.8–152, 206–275, 514–637, 131–179, 18.5–27.0, 1.31–1.75, and 6.11–8.11 for the F5, respectively. Overall, Cd and Fe showed the least and highest distributions in the various geochemical forms, respectively. Moreover, the abundance and mobility of Mn, Ni, Fe, Cr, Cd, and Zn correlated significantly in exchangeable and carbonate-bond fractions. Hence, environmental monitoring of the sediments and Pisces should be carried out while remediation of the location is recommended.