DISTRIBUTION PATTERNS AND AVAILABILITY OF HEAVY METALS IN SOILS IN THE VICINITY OF AN OPEN DUMPSITE IN WARRI, NIGERIAHELEN ATAIKIRU AND F.E. OKIEIMEN
The total and spatial variations of Cr. Pb, Zn and Mn concentrations in the soil samples collected from Esisi open dumpsite in Warri were determined and used to evaluate the anthropogenic pollution status of the soils and the apparent spatial variations of the metals in subsurface soil in the vicinity of the dumpsite. The speciations of Cr, Pb, Zn and Mn in the soil were determined to ascertain the potential public health hazard presented by the heavy metals. Aggregate test soil samples were collected from Esisi dumpsite, background soil samples were also collected at about 2 km from the dumpsite and spatial test samples were collected at various increasing distances 5-100 m from the epicenter of the Esisi dumpsite using a stainless steel augur. The physico-chemical properties, pH, TOC, CEC, the soil textural class and the total metal content of the soil samples were determined using standard procedures/methods. The soil pH was determined in water, a 1:1 soil / water slurry using a suntex digital pH meter according to the method of Folson. Total organic carbon was determined using the Walkley-Black rapid oxidation method. In order to assess the geochemical forms and bio available Mn, Cr, Pb and Zn in the soil of the open dumpsite, Tessiers sequential extraction procedures were employed. The concentrations of heavy metals ( Mn, Cr, Pb and Zn) in the various extracts were determined in a pre-calibrated atomic absorption spectrophotometer. The total metal concentrations of Pb, Cr, Mn and Zn reported in this study were higher than background samples values. The heavy metal assessment indices indicated that the soils in the vicinity of the open dumpsite were highly polluted. The metals were found mostly in the Fe-Mn oxide fraction of all the soils analyzed. This study has provided data and information on the chemical forms of the heavy metals of environmental concern in the soils in the vicinity of Esisi open dumpsite. The data obtained suggest environmental risk of the metals in the vicinity of the dumpsite in Warri metropolis.
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