[01] Abata Emmanuel Orimisan, Department of Chemistry, School of Sciences Federal University of Technology, Akure, Nigeria. [02] Victor Oluwatimilehin Dada, Department of Chemistry, School of Sciences Federal University of Technology, Akure, Nigeria. [03] Micheal Oluwasen Fatukasi, Department of Chemistry, School of Sciences Federal University of Technology, Akure, Nigeria. [04] Joshua Akinropo Oyetade, Department of Chemistry, School of Sciences Federal University of Technology, Akure, Nigeria.

The total digestion method for determining the mobility and bioavailability of metals in sediments is not enough to fully evaluate the ecological impact of these heavy metals; hence the need for speciation is important by understanding its geochemical forms. Prior to the sequel extraction, certain parameters this includes determination of the sediment pH with the use of pH meter alongside its conductivity. The sequential extraction method involving was used to determine the distribution of heavy metals. The heavy metals studied are Iron, copper, zinc, lead, and cadmium from five distinct fractions prepared by the selection of five sampling area under study. The physicochemical parameters investigated for the fractions are classified as water soluble, exchangeable, carbonate, Fe-Mn oxide, organic and residual. The Fe-Mn oxide fraction has the highest amount in iron (42.9%), while exchangeable fraction has its highest amount in copper, zinc and lead were bound in non-residual fraction while residual has its highest amount in cadmium. The bioavailability of these metals can be related to the solubility of the geochemical forms of the metals. Therefore the mobility for these metals in the sediments are in decreasing order are; Iron > Lead > Zinc > Copper > Cadmium. The pH and electrical conductivity of these locations were found to range within the slightly acidic medium (5.26 – 6.02) and 30.5 – 53.0 µs/cm respectively. The values of the heavy metals from the result showed that Iron and lead was appreciably associated with the non-residual fractions in the sediments and thus, more potentially bio-available in comparison to other heavy metal studied. The residual fraction was discovered to consist of Copper, zinc, and Cd having average values of 73.2%, 67.6%, and 96%. However, Iron was found to bioavailable in the entire fraction with the highest% in Fe- Mn. It can be deduced that these metals (i.e. Copper and Zinc) possess low mobile fraction consequently, has a low potential risk for the aquatic life. Lead, on the other hand, has the highest portion in the mobile fraction and thus poses a high risk to aquatic environments.

Sediments, Metals Speciation, AlaRiver, Heavy Metals

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