Monitoring and Assessment of Heavy Metals Contamination in Surface Water and Sediments in Bonny Estuary, Niger Delta

The study of heavy metals contamination on surface water, and sediment in the Upper Bonny Estuary was investigated. Samples of surface water, and sediment were collected at 5 selected stations namely: Okochiri River (S1), Ekerekana Creek (POD, S2), Okari-Ama River (S3), Ogoloma Creek (S4) and Bonny Estuary (Control, S5). Physico-chemical parameters (pH, temperature, DO, conductivity, salinity, TDS, TOC, and THC) were analyzed according to standard procedures for surface water (APHA), while heavy metal parameters (As, Cd., Cr, Pb, Hg, V and Zn) were analyzed for water, and sediment using Atomic Absorption Spectrophotometer. The results obtained indicated that the physico-chemical parameters varied significantly (P < 0.05). These parameters such as pH, temperature, conductivity, salinity, TDS and TOC were higher in the dry season while, THC was higher in content it presents above the permissible limit of 20 mg / l (FMEnv) at the point of effluent discharge (Ekerekana Creek S2) during the wet season and TDS in all sampled measured were above permissible limit. However, DO were values below FMEnv of 5.0 mg / l in most sampled stations in both seasons. Heavy metals (As, Cd, Cr, Pb, Hg, V and Zn) analysed were below detectable limit in water. Total metal content in sediment were higher than the levels recorded in water. The mean concentration in sediment was in the order Zn >Pb> Ni > V> Cd. As and Hg were not detected in the study. The degree of contamination in sediment revealed that the Contamination Factor of the studied metals in both seasons were all <1 except Pb during the dry season in (S4) and (S5) which were (1.07 mg/kg and 1.05 mg / kg) respectively. Further indices using Pollution Load Index (PLI) and Geo-accumulation Index (Igeo) revealed <1 in all the stations in both seasons. Comparison with USEPA (SQG) and WHO (SQG), proved that the levels of heavy metals were below permissible limit in the sampled stations.