Environmental impacts assessment of shipping activities on water quality of Apapa Bay, Lagos, Nigeria

Activities at seaports can contribute to ecological hazards, particularly water pollution. This study investigated the environmental impacts of shipping activities at Apapa Bay, Lagos, Nigeria, focusing on the physicochemical characteristics and potentially toxic metals (PTMs) in the water. Water and sediment samples were collected from four different terminals in Apapa Bay and from Takwa Bay, which served as a control site due to its lack of shipping activity. The surface water of Apapa Bay exhibited the following ranges: temperature 26.35 to 27.38ºC, pH 7.03 to 7.85, conductivity 1100 to 1588 µS/cm, and total alkalinity 72.85 to 77.28 ± 0.41 mg/l. The biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) values ranged from 36.5 to 72.4 mg/l and 199.1 to 236.7 mg/l, respectively, both exceeding permissible limits. Low concentrations of phosphate (0.363 to 0.652 mg/l) and sulfate (11.10 to 36.92 ± 14.10 mg/l) were recorded. PTM concentrations in Apapa Bay ranged as follows: Cd (1.210 to 3.024 mg/kg), Fe (30.000 to 35.625 mg/kg), Pb (1.756 to 65.902 mg/kg), and Cu (10.859 to 13.423 mg/kg), compared to Takwa Bay concentrations of 0.600, 6.876, 8.585 and 10.859 mg/kg, respectively. Sediment Quality Guidelines (SQGs) were applied to assess metal toxicity risks. Significant (p < 0.05) correlations were observed among Cd, Pb, Fe, and Cu, suggesting similar sources for these metals. According to the SQGs, Apapa Bay is classified as heavily polluted in terms of Cd and Fe, but non-polluted for Pb and Cu. These findings provide baseline data for future policies aimed at protecting the marine environment of Apapa Bay.   Key words: Bay, terminal, physicochemical, potentially toxic metals, pollution.