Evaluating the Pollution Levels and Ecological Risks of Heavy Metals in Sediments of Apapa Port in Lagos, South-western Nigeria

Abstract

The coastal sediments of Apapa Port in Lagos, Southwestern Nigeria were studied to determine the status of contamination due to the present of heavy metals and its effect on the ecosystem. The sediments samples were subjected to Particle Induce X-ray Emission (PIXE) technique analysis to determine heavy metals present in them. Ten (10) heavy metals were detected with which their concentrations ranged as Ti (2787.0 - 5672.9 mg/kg), Cr (95.4 - 285.9 mg/kg), Mn (124.8 - 526.7 mg/kg), Fe (20263.7 – 49953.7 mg/kg), Cu (8.0 – 13.4 mg/kg), Zn (280.1 – 1246.5 mg/kg), Rb (58.6 – 336.1 mg/kg), Sr (39.3 – 233.5 mg/kg), Zr (89.3 – 190.1 mg/kg), and Pb (13.3 – 31.1 mg/kg). The extent of contamination of the heavy metals was enumerated by comparing their concentrations with the USEPA guidelines, TEL and PEL. Different pollution indices such as enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), modified degree of contamination (mCd), pollution load index (PLI), and potential ecological risk index (PERI) were applied to estimate the level of toxicity imposed on the ecosystem by the detected heavy metals. These showed that the studied sediments were severely enriched with Zn at site 5 and moderately enriched with Cr and Rb at stations 5 and other respectively but the sum of all risk factors for those heavy metals is low. Statistical analysis such as the cluster analysis and Pearson’s correlation coefficient were also employed to determine the relationships of those heavy metals with respect to their origin. These revealed strong positive and negative correlations among the heavy metals and are cluster in terms of similarities as (1) Ti-Fe-Mn (2) Rb-Pb (3) Sr (4) Cu-Zn-Cr-Zr. This studied area requires proper monitoring to avert increase in ecological risk factor due to anthropogenic influences.