Assessment of levels of contamination and estimation of ecological risk by potentially toxic elements in Chanchaga River of Minna, Nigeria

Abstract

This research investigated the geochemical characteristics, contamination indices and ecological risk assessment of stream sediments from Chanchaga area of Minna Metropolis, North-Central Nigeria. Eight samples were collected from River Chanchaga and its tributaries and sieved to less than 2 mm grain size following air drying for 48 hours. The samples were subsequently analysed for the concentration of major and trace elements using X-ray fluorescence (XRF) spectrometry. Contamination indices (enrichment ratio, enrichment factor and index of geoaccumulation) and potential ecological risk index (PERI) were used for assessing the level of risk that exists with respect to potentially toxic elements (PTEs). The research has found significant enrichment of Pb and Cu in stream sediments of Chanchaga area, indicating possible contamination by human activities. Based on the indices of geoaccumulation, the sediments are considered to be moderately to heavily contaminated with respect to these two PTEs. Potential ecological risks exist with respect to PTEs in these sediments, with PERI values in the range of 12.88 to 167.76, averaging 58.63. Pb presented higher monomial ecological risk index, falling within the considerable risk band and contributed significantly to the PERI values, compared to that of Cu. It is therefore concluded that human activities within Chanchaga area of Minna metropolis, Nigeria have had a negative impact on stream sediment quality and there is likelihood of mobilisation of PTEs into the water column from sediments under right environmental conditions. It is recommended that the partitioning of PTEs, especially Pb and Cu in these sediments be studied in order to ascertain their ease of dissolution and eventual biogeoaccessibility.