INVESTIGATION OF THE IMPACT OF POTENTIALLY TOXIC ELEMENTS FROM URBAN FLOODED AREAS IN PORT HARCOURT CITY, NIGERIA

Abstract

Flooding transports significant environmental contaminants in soils especially potentially toxic elements (PTEs). The prevalence of PTEs in the environment poses serious threat to human health. Anthropogenic activities contribute to elevation of PTEs contents in soils. In this study, a total of 24 soil samples collected from six study areas within Port Harcourt city were analysed to determine level of some elements (As, Cd, Cr, Pb and Ni) following the acid digestion methods. Samples were taken from different soil profiles ranging from topsoil (0 – 30 cm) to sub-soil (30 – 60 cm). Each sample was subjected to three acid digestion procedures namely: aqua regia, reversed aqua regia and multi-acid attack. For purposes of quality control, levels of the elements of interest in the digested samples along with blanks were measured using atomic absorption spectrometer (AAS). A wide range of total concentrations of the toxic elements was found, with high level of concentration obtained in the topsoil. The proportion of elements released by the multi- acid attack method was higher than those of aqua regia and reversed aqua regia methods. This finding suggests that the heavy metals bound to silicate minerals are not easily dissolved in simple mineral acids. A correlation analysis revealed a strong association between Pb and total organic carbon (r = 0.950012), indicating that the source of Pb contaminants may be derived from organic matter contents. The potential health risk associated with PTEs indicated non-carcinogenic risk for children and carcinogenic risk for adults living in the flooded areas. Further monitoring of flooded areas in Port Harcourt metropolis is recommended for other environmental contaminants beside the PTEs monitored.