Application of pollution assessment models in soil contaminated by heavy metals in two steel rods markets, Port Harcourt, Rivers State, Nigeria

Abstract

Soil samples were collected at a depth of 0-30cm within two steel markets and a control site in Port Harcourt, Rivers State Nigeria to assess the level of heavy metals (Fe, Pb, Cu, Cd, Cr, Ni and As) in the environment. Atomic Adsorption Spectrophotometer was used to analyze the samples for heavy metals. The concentrations of all the heavy metals in the steel rods markets exceeded that of the control. The results indicated that heavy metals concentrations in the sites were in the order; Mile III > Kala > RSU. The average levels of contamination of heavy metals recorded followed the order Fe > Cr > Cu > Pb > Ni > As > Cd in Mile III, Fe > Pb > Cu > Cr > Ni > As > Cd in Kala and Fe > Cu > Pb > Cr > Ni > As > Cd in RSU (control). Mean concentrations obtained for heavy metals within the months of investigation were; 1420.931±9.155, 7.753±0.184, 8.730±0.050, 2.843±0.124, 9.428±0.122, 7.433±0.047 and 3.732±0.047 mg/Kg for Fe, Pb, Cu, Cd, Cr, Ni and As respectively at the mile III station, while the mean concentrations of heavy metals observed at the Kala station were; 1161.173±1.823, 9.425±0.054, 7.596±0.027, 1.425±0.020, 6.507±0.006, 5.455±0.033 and 1.901±0.010 mg/Kg for Fe, Pb, Cu, Cd, Cr, Ni and As respectively. The mean values of heavy metals concentrations observed at the RSU station within the period were; 892.064±1.025,5.603±0.007, 5.841±0.051, 0.173±0.005, 3.389±0.009, 2.309±0.010 and 0.706±0.006 mg/Kg for Fe, Pb, Cu, Cd, Cr, Ni and As respectively. Pollution assessment models used for assessing the anthropogenic input on the quality of the soil in the area using the control site as the basis of judgment were: contamination factor (CF), pollution load index (PLI), contamination degree (CD), modified contamination degree (mCD), potential ecological risk coefficient (Eir), potential ecological risk index (RI), Geo-accumulation index (Igeo) and anthropogenicity. These indices revealed that the steel markets were contaminated and polluted and poses ecological risks by heavy metals, even though the values obtained were still below the WHO acceptable limits. The steel rods markets need to be adequately monitored and regulated to avoid further soil contamination by heavy metals to a degree that will be dangerous to human health.