Assessment of Qualities of Surface Water, Sediments and Aquatic Fish from Selected Major Rivers in South-Western Nigeria

Available sources of portable water for drinking, domestic and industrial chores in Nigeria are dwindling because of concomitant increase in population, urbanization and industrial activities. This study assessed the qualities of Surface Water (SW), Sediment (SD) and Tilapia Fish (Oreichromis niloticuss) (TF) samples collected from Asejire, Oni, Ona, Ogun, Ogunpa, Eleyele and Majidun rivers and Lagos lagoon in south-western Nigeria. Samples of SW, SD and TF were collected at strategic locations from each water source and analyzed using standard procedures. SW for all locations were grossly polluted with organics as indicated by high COD (72.8-292 mg/L) and BOD (30.8-143 mg/L) and low DO (1.04-6.68 mg/L) levels. Lead levels in SW for all locations exceeded WHO and NIS limits for drinking water. Cadmium levels in sediments from Oni, Ona, Ogun and Ogunpa rivers also exceeded Canadian Interim Sediment Quality Guidelines (ISQG) of 0.6 mg/kg. Fish from Lagos lagoon were most polluted with Pb, Cr, Ni and Cu. Principal Component analysis showed that 86.4% of overall metal load for SW was from Ogunpa and Eleyele rivers, whereas 62.9% metal load for S was from Ogunpa, Eleyele and Ogun rivers. The metal pollution index order was Pb>Cu>Co>Ni>Cr>Cd. Lead and nickel showed strong positive correlation between SW and SD, suggesting common source while Pb and Cr showed strong negative correlation with Cd between SW and TF. Unsafe disposal practices of wastes into or within the vicinity of water bodies should be discourage.