Asian Journal of Current Research

This study assessed the concentrations, spatial distribution and pollution status of selected heavy metals in surface water and sediment from the Mini-Welele River in Mgbuosimini Community, Obio/Akpor Local Government Area, Rivers State, Nigeria. Five sampling stations were established along the river to represent sections influenced by different levels of settlement, drainage and other human activities. Surface water samples were collected in clean acid-washed polyethylene bottles, preserved with nitric acid, digested and analysed by flame atomic absorption spectrophotometry. Surficial sediment samples were collected from the same stations, air-dried, homogenised, sieved, acid-digested and analysed for metals using the same instrumental technique. Surface water was analysed for Cd, Cr, Cu, Fe, Pb, Mn and Ni, while sediment was analysed for Cr, Pb and Ni. Because only station-level mean concentrations were available, the data were treated descriptively using ranges, means, standard deviations, total metal burden, comparison with guideline values and sediment pollution indices. Surface water mean concentrations followed the order Fe (1.480 mg/L) > Pb (0.658 mg/L) > Ni (0.514 mg/L) > Cr (0.353 mg/L) > Cd (0.141 mg/L) > Mn (0.119 mg/L) > Cu (0.070 mg/L). Cr, Fe, Pb, Ni and Cd exceeded the guideline values used for screening comparison, while Cu and Mn were below the respective comparison limits. Sediment mean concentrations followed the order Pb (49.18 mg/kg) > Cr (35.26 mg/kg) > Ni (19.56 mg/kg). Contamination factor values indicated low to moderate Cr contamination, moderate to considerable Pb contamination and low Ni contamination. Geoaccumulation index values generally indicated unpolluted to moderately polluted sediment conditions, while pollution load index values below 1 suggested no overall combined pollution load for the sediment metals assessed. The findings show measurable heavy metal inputs into the Mini-Welele River, particularly in surface water and Pb-enriched sediment zones. Routine monitoring, waste-control enforcement, community awareness and more detailed seasonal studies are recommended.