Health and Ecological Risks Associated with Heavy Metal Contamination in Surface Soils from Lagos Lagoon Wetlands, Lagos, Nigeria

Abstract

Wetlands quality and spatial distribution are being threatened by anthropogenic drivers in addition to the emerging threats of climate change. In this study, selected heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in soils from Lagos lagoon wetlands were investigated to assess spatial distribution, ecological and health risks. The data obtained were subjected to statistical analysis using GraphPad 7.0 and SPSS 22.0. Spatial distribution mapping of heavy metals was performed using ArcGIS10.0 (ESRI, Redlands, CA, USA) with Kriging interpolation. Results showed that heavy metals in the soil varied significantly (p<0.05). The contamination factors (CF) were generally low with the values for Cr, Ni, Cu, and Zn very low (<1). The CF values for some of the sampling points showed that the soils are generally moderately contaminated by Pb, Cd and Cu. The modified degree of contamination of Pb (2.35) indicates a moderate degree of contamination while that of Cd (12.60) indicates a high degree of contamination of these wetland soils. The potential ecological risk index (RI) of Pb, Cd, Cr, Ni, Cu and Zn were 70.40, 2264.40, 0.68, 1.55, 13.65, and 2.29, respectively. The RI for Pb, Cr, Ni, Cu and Zn were less than 100, hence, low, while the RI value of Cd was a very high risk (RI ≥ 400). Soils from this wetland’s areas show serious significant potential ecological risk due to Cd. Additionally, children were more susceptible to the potential health risk irrespective of the carcinogenic or non – carcinogenic risk. There were no significant carcinogenic and non – carcinogenic risks for adults and children. This wetland assessment provided important information for policymaking to reduce the potential effects of soil contamination on humans and the eco-environment.