SOLID-PHASE FRACTIONATION OF HEAVY METAL IONS IN SOILS FROM MUNICIPAL WASTE DUMPSITE IN PORT HARCOURT, NIGERIA

In many cities across the developing countries solid wastes are disposed indiscriminately without recourse to the human health risk. Heavy metals found in solid wastes may likely be released into the environment via flood runoff. To assess whether the contaminants can affect the groundwater, soil samples were collected for analysis in two seasons – dry and wet seasons. To determine level of the metals in the soil matrix, the samples were subjected to acid digestion followed by atomic absorption spectroscopy analysis. The different solid-phases associated with heavy metals were evaluated from the soil samples by using sequential extraction method. The geo-accumulation index and mobility factor were considered to assess the level of contamination and migration of the metals present in the soil. The soil metal contents strongly correlated with the soil pH and organic matter. The exchangeable fraction has Cr > Pb > Co in the order of its mobility in the soil, whilst in the residual fraction suggesting the most immobile species with Pb > Co > Cr > Ni present in the soil. The geo-accumulation index showed that the degree of pollution of the dumpsite during the dry and wet seasons was mostly unpolluted. The study indicates that the metals of interest may not likely pose environmental risk due to their relatively low concentrations and the chemical species in which they exist in soil.