Geochemical study of heavy metals in samples from dumpsites at Onitsha, Anambra Basin, Southeastern Nigeria

Core (0-60cm) samples were collected from selected dumpsites at Onitsha and control site at Awka, Nigeria. Physiochemical parameters (particle size distribution, cation exchange capacity (CEC), pH, Organic Matter (OM in %)) and heavy metals (Lead (Pb), Copper (Cu), Zinc (Zn), Chromium (Cr), Nickel (Ni), Aluminium (Al), Cobalt (Co), Molybdenium (Mo), Cadmium (Cd), Manganese (Mn) and Silicon (Si)) were analyzed using standard methods. The result of the physiochemical analysis shows that the samples were generally sandy with acidic pH values (4.89-6.24); OM ranged from 5.693-27.71%; CEC ranged from 0.072-0.62(Cmol/kg). Comparatively, DS 5 (Obosi) has the highest levels of these heavy metals followed by DS 2 (Woliwo). The order is Bida < Okpoko <Obosi 1 < Woliwo < Obosi 2. The levels of these heavy metals were above the control values. They were equally above national and international guidelines. Enrichment Factor (EF) values varied between no enrichment to extremely severe enrichment. Pollution load index (PLI) indicated that all the sampled sites were polluted while the ecological risk of heavy metals varied between low contamination to high contamination. The prevailing indiscriminate disposal of wastes occasioned by nonexistence of appropriate disposal facilities is the direct cause of the situation. Proactive measures and regular environmental monitoring must be taken to minimize further deterioration as the contaminants pose serious deleterious effects on human and soil organisms.