Ecological risk assessment of potentially toxic elements in the bottom sediments of a stream in Oke-Ere, Kogi State, North Central Nigeria

Sediments absorb and accumulate toxic elements, which might be re-activated and easily released into the water body, which could be a serious ecological risk to the aquatic ecosystem. It is a vital environmental medium widely used for characterizing anthropogenic contaminants. This study assessed the extent of pollution and the ecological threat posed by potentially toxic elements in the bottom sediment of a stream in Oke-Ere, Kogi State, North Central Nigeria. A total of 72 samples were collected and analyzed with inductively coupled plasma mass spectroscopy (ICP-MS), after acid digestion. The data obtained were subjected to simple descriptive and inferential statistics. Sediment pollution levels and ecological risk were evaluated based on models of sediment quality guidelines (SQGs), geo-accumulation index (I-geo), enrichment factor (EF), pollution load index (PLI), contamination factor (Cf), and potential ecological risk (E-r(i)). Based on SQGs, average levels of Zn, Pb, Cr, and Cu exceeded the threshold effect concentrations (TEC), but no collective toxicity from the studied elements as the value of mPEC-Q was < 0.5. The pollution indices studies (I-geo, EF, PLI, and Cf) revealed that the bottom sediment samples were low to moderate contaminated with the investigated elements and ecological risk revealed that the bottom sediment samples were within the low to moderate class, and Mo contributed 56% of the total potential ecological risk. However, appropriate measures should be taken to avoid serious ecological risks to the study area.