Trace Metal Contamination Characteristics and Health Risks Assessment of Commelina africana L. and Psammitic Sandflats in the Niger Delta, Nigeria

Abstract

The purpose of this study was to investigate and quantify trace metal concentrations in Commelina africana L. and psammitic sandflats from an intertidal coastal ecosystem in Niger Delta, Nigeria, and to evaluate their spatial distribution, degree of contamination, and source apportionment. The environmental risks associated with soil contamination were elaborately assessed using potential ecological risk index, sediment quality guidelines, and enrichment relative to background levels. The mean concentrations of Cd, Cr, Ni, Pb, and Zn in sandflat soil samples are 0.76±9.0×10-2, 7.39±8.7×10-1, 2.28±0.35, 0.024±4.0×10-3, and 74.51±2.55 mg/kg, respectively. Metal levels indicate strong variability with sampling sites. The order of trace metal concentrations in the Commelina africana L. samples is Zn>Ni>Cr>Pb>Cd. The concentrations varied with the sample locations; and the levels of Pb (0.05 to 0.08 mg/kg) at all locations are found to be significantly below permissible level of 0.3 mg/kg. Potential sources of metal loadings may be associated with localised or diffused anthropogenic activities. The average carcinogenic risks are below 1.0×10-6 threshold values, and the sandflat soils are not considered to pose significant health effects to children and adult males and females. However, the carcinogenicity and noncarcinogenicity risks ranking decrease following the order children>adult males>adult females. Comparatively, the hazard quotient and hazard index indicate that the psammitic sandflats might pose a health risk to children in future.