Assessment of Heavy Metal Levels, Pollution Indices and Ecological Risks of Floodplain Sediments in Urban Areas in Delta State, Nigeria

The aim of this study is to assess heavy metals levels, pollution indices and ecological risks of floodplain sediments in urban areas in Delta State, Nigeria. The levels of nine heavy metals (Cd, Pb, Cr, Ni, Cu, Co, Mn, Zn and Fe) were measured in floodplain sediments of urban areas in Delta State, Nigeria. Sediment samples from the nine urban areas were collected for three months (July-September) covering the wet season. The sediment samples were digested with aqua regia, and the heavy metal levels in the digests were quantified by means of atomic absorption spectrometry. The levels of heavy metals in the sediments were: Cd 1.13-7.38, Pb 5.05-8.05, Cr 4.16-9.17, Ni 3.48-4.48, Cu 7.49-12.9, Co 6.27-14.2, Mn 310-744, Zn 71.3-133 and Fe 1036-1692 mg kg-1. The results showed significant spatial variation in the metal distribution patterns. The pollution indices suggested that Cd is the main heavy metal contaminant in the floodplain sediments. The ecological risk indices indicate that very high ecological risks are associated with exposure to these heavy metals but with significant impact from Cd.