Pollution status and ecological risk of heavy metals in surface water and sediment of the coastal creeks of Ondo state, Nigeria

Abstract

Despite the irreplaceable value of the aquatic ecosystem to livelihoods, the continuous release of heavy metals into the marine environment have remained an issue of global concern due to their bioaccumulation, and potential toxicity in biological systems and humans. This study investigated the Pollution Status and Ecological Risk of Heavy Metals in Surface Water and Sediment of the Coastal Creeks of Ondo State. Water and sediment samples were collected from four stations between June, 2019 and April, 2021. Heavy metals in the samples were analyzed with GBC Savant AA Sigma Flame Atomic Absorption Spectrometer (AAS). The results of the mean level of heavy metals were in the order; Fe>Zn>Cu> Ni> Co>Pb> Cd>Cr for surface water; and Fe> Cu> Co> Ni >Zn > Pb > Cr> Cd for sediment. The single-factor pollution index revealed slight to serious pollution of the water, and low to moderate pollution of the sediment. The degree of contamination (Cd) and the geoaccumulation factors (Igeo) of individual metals were also low. The ecological risk (Er) of individual metal showed low risk in the sediment, except for Cadmium that showed moderate risk (40<Eir ≤ 80) across the stations. On the other hand, the potential ecological risk (RI) revealed low risk (RI <150) of heavy metals in the sediment. The enrichment factors (Ef) for individual metals were greater than 40 (Ef ≥40), which suggests extremely high enrichment of heavy metal in the sediment through anthropogenic sources. This study provided insights into the pollution status of the surface water and sediment of the coastal creeks of Ondo state and it associate potential ecological risks.