Geochemical assessment of heavy metal impact on soil around Ewu-Elepe Dumpsite, Lagos State, Nigeria

Abstract

The concentrations of certain heavy metals in the top soils around the Ewu-Elepe dumpsite and its environs were determined with a view to  ascertaining the level of metal pollution in the soils of the dumpsite vicinity. Thirty-two (32) soil samples were randomly collected within the dumpsite vicinity and one control sample was collected from a distance of about 9.0 km from the dumpsite. The samples were prepared according  to standard procedures and analyzed for some heavy metals (Ni, Mn, Co, Cd, Cu, Pb, and Zn) using the Atomic Absorption Spectrophotometer at the Geochemistry Laboratory of the Department of Geology, Obafemi Awolowo University, Ile-Ife. The geochemical data was subjected to both  univariate and multivariate statistical treatments and comparisons were made with various world standards. The results obtained showed that the mean concentrations of Ni (12.00 ppm), Mn (525.60 ppm), Co (5.64 ppm), Cu (44.59 ppm), and Zn (105.28 ppm) were within the acceptable limits for agricultural soils while those of Cd (1.40 ppm) and Pb (33.74 ppm) exceeded the limits. Geo-accumulation index and contamination factor revealed that the soils around the dumpsite were moderately contaminated with Cd and slightly contaminated with Pb. The overall decreasing order of heavy metal concentration in the dumpsite soil is: Cd > Pb > Zn > Cu > Mn > Co > Ni. The study concluded that the soils around the Ewu-Elepe dumpsite was contaminated with Cd and Pb and as such should be discouraged in its usage for agricultural related purposes as these highly toxic trace elements can be absorbed by plants. A well-engineered landfill that takes into consideration the local geology and the topography of the area should be designed so as to prevent infiltration of leachates into the soil and shallow groundwater systems.

Keywords - Heavy metals, Soil,Ewu-Elepe,Nigeria,Dumpsite,Contamination.