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.
 
 
Highlights
Wetlands are distinct ecosystems that are inundated by water, either permanently or seasonally, with their characteristic vegetation of aquatic plants, adapted to the unique hydric soil (Keddy, 2010)
Wetland soils pollution by heavy metals has been regarded as a critical problem because of their toxicity, persistence, and bioaccumulation (Njoku et al, 2013; Adesuyi et al, 2018)
Our primary aim was to determine the distribution of heavy metals, evaluate the degree of heavy metal pollution based on contamination factor, pollution index, ecological risk indices and the health risks associated with the wetland soils
Summary
Wetlands are distinct ecosystems that are inundated by water, either permanently or seasonally, with their characteristic vegetation of aquatic plants, adapted to the unique hydric soil (Keddy, 2010). Wetland soils pollution by heavy metals has been regarded as a critical problem because of their toxicity, persistence, and bioaccumulation (Njoku et al, 2013; Adesuyi et al, 2018) They adversely affect ecosystems, and they can be associated with direct and indirect human health risks when they pollute soils. Metals without known biological functions (such as lead, cadmium and arsenic) and even some essential metals for human beings (copper, zinc and chromium) can cause health risks when present in excess levels Some metals, such as Pb, As, Cd and Cr have been classified as carcinogenic elements by the International Agency for Research on Cancer (Bai and Zhao, 2020). The ecological risks assessment is part of the contemporary research in soil pollution studies and environmental management, it indicates the tendency of the adverse effects of heavy metals on the ecological health (Ogundele et al, 2020). Our primary aim was to determine the distribution of heavy metals, evaluate the degree of heavy metal pollution based on contamination factor, pollution index, ecological risk indices and the health risks associated with the wetland soils
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