Heavy Metal Contents of Effluents and Receiving Waters from Various Industrial Groups and their Environs in Ibadan, Nigeria

The effluent and receiving water and soil quality from thirty three industries from seven different industrial groups, namely: Food (10), Chemical (6), Plastic (7), Pharmaceutical (2), Steel (4), Cardboard (2) and Glass (2) in Ibadan metropolis was investigated. Heavy metals (cobalt, chromium, copper, iron, magnesium, manganese, lead and zinc), anion (nitrate and chlorides) and cation (phosphate and ammonium) contents of the samples were determined using standard methods. Results show that soils around food and chemical industries had significantly higher (p< 0.05) heavy metal contents. Soil lead content around food and chemical industries are significantly higher (p< 0.05) than values obtained for effluents, receiving waters and plants in their environs. Lead content is highest in soils (2.48 mg L 1) but lowest in the effluents discharged (0.13 mg L 1), the receiving water (0.22 and 0.25 mg L 1) and plants (0.28 mg L 1) around steel industries. A similar pattern was observed for Pharmaceutical and Glass Industries. Pb discharge is highest in effluents from Cardboard and Paper industries while significantly lower values were obtained for the other industries. Lead contents are 0.14, 0.21, 0.17, 0.21 mg L 1 and 0.12, 0.19, 0.12 and 0.19 mg L 1 in the effluent, plants, upper receiving and lower receiving waters in soils around chemical and plastic industries, respectively. Magnesium and cobalt, manganese and magnesium, manganese and cobalt, cobalt and zinc were highest in effluents released by steel, cardboard, pharmaceutical and glass industries, respectively.