Pollution indices and ecological risk assessment of major elements and trace metals in the marine sediment of the western Nigeria continental shelf, Gulf of Guinea

• Published in: Scientific African 2023-11, Vol.22, p.e01923, Article e01923
• Main Authors: Popoola, Samuel Olatunde, Nubi, Ayoola Olubunmi, Unyimadu, John Paul, Ladigbolu, Ismail Adejare, Fabunmi, Idera, Udochu, Ugo, Nwamba, Elizabeth, Oba, Ismaila Ayinde, Mordi, Solomon, Adamu, Salisu
• Format: Article
• Language: English
• Subjects: Baseline compositions; Ecological risk index (RI); Gulf of Guinea; Major and trace metals; Pollution indices; Sediment core
• ISSN: 2468-2276; 2468-2276
• DOI: 10.1016/j.sciaf.2023.e01923

•Major and trace metals were investigated from sediment cores of the Gulf of Guinea, off the Nigerian Coast.•The results showed that mean concentrations of metals were lower than their corresponding background and toxicity threshold values except As and U.•PCA, CF, lgeo, EF, PLI, and RI revealed the metals are geogenic.•This study will serve as a preliminary baseline chemical composition for rational ecological protection measures. The Gulf of Guinea is known to be highly productive owing to its ecological and economical significance. Given its importance, detailed evaluation of the major elements (Fe, Mn, Ca, Mg, Na, Al, K and Si) and trace metals (Cu, Zn, Pb, Cr, Ni, As, Sc, V, Th and U) were analyzed from the sediment core within this basin for the first time. This study aims to determine their baseline composition, pollution level, and ecological risk. Analyses of these metals using inductively Coupled Plasma Optical Emission Spectrophotometer (ICP-OES) with Agilent SPS3 Autosampler showed the descending order of Na > Fe > Ca > Si > Mg > Al > K > Mn and Zn > U > V > Ni > Cr > Th > Pb > As > Cu > Sc for major and trace element respectively. The pollution indices and sediment qualities were assessed using the contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), potential ecological risk factor (Er), modified hazard quotient (mHQ), pollution load index (PLI), ecological risk index (RI), single metal toxic risk index (TRIi) and integrated Toxic risk index (TRI) at three stations (stations A, B, and C). Except for As and U, the mean concentrations of the metals were lower than their respective background values. Based on the pollution indices, the studied trace metals were found to have severe EF (>25) with respect to Zn and V, considerable CF (3 ≤ CF ≤ 6) for As, and high CF (> 6) for U. The Igeo values of all the trace metals indicated unpolluted to moderately polluted status (0 ≤ lgeo ≤ 1). The Er ranges (0.05–41.80) indicate low to moderate ecological risk, while mHQ (< 1) values indicate very low severity of contamination. There was no significant risk from the combined metals recovered from the sediment core of the study area to the marine ecosystems according to RI (