Concentration, ecological risk and enrichment factor assessment of selected heavy metals in sediments from New Calabar River, Nigeria

Abstract

The New Calabar River is an important commercial river in Rivers State. Surface sediment samples were collected from four stations and analyzed for some heavy metals concentrations. The results obtained revealed that the concentrations of the metals were iron (Fe) > zinc (Zn) > nickel (Ni) > chromium (Cr) > copper (Cu) > lead (Pb) > cadmium (Cd) > arsenic (As). Their respective mean values were; Fe, 147.84±90.13; Zn, 5.49±2.01; Ni, 3.50±1.48; Cr, 3.42±1.00; Cu, 2.48±1.11; Pb, 2.42±1.09; Cd, 0.089±0.12 and As, 0.006±0.005 mg/Kg. The results were further evaluated with some model indices (contamination factor, ecological risk and enrichment factor assessments. Sediment contamination factor analysis showed that the sediments were slightly contaminated. Ecological risk assessment revealed that the metals at the present concentrations are not harmful or cannot cause risk to the environment. However, enrichment factor analysis indicated that all the metals had significant anthropogenic enrichment at the various stations except As at Aluu, Choba and Iwofe and Cd at Aluu. Therefore, adequate and continuous monitoring should be put in place to prevent upsurge of anthropogenic heavy metals input into the river.

Keywords: Heavy metals, ecological risk, enrichment factor, sediment quality