Geochemical and Geotechnical Characteristics of Soil within Oke-diya Dumpsite in Sagamu South Western Nigeria

Abstract

This research was to determine geotechnical and geochemical characteristics of soil around Oke diya dumpsite in Sagamu Southwestern Nigeria. Five soil samples were collected within dumpsite at depth of 0-20 cm to determine their engineering properties in accordance with the British Standards. Another eight (8) soil samples were collected vertically at the depth of 1m interval for geochemical analysis using Inductively Coupled Plasma-Mass Spectrophotometer method (ICP MS). The specific gravity value ranges between 2.78–3.00 which fall within moderate degree of laterization and dehydration. The soil generally can be classified as silty sand of intermediate to high plasticity or compressibility based on the percentage grain size distribution and Casagrande Plasticity Chart. Permeability tests showed low permeability within the range of 1.8 x 10-6 cm/s – 2.12 x 10-6 cm/s. Therefore the soil has capacity to provide long term protection of groundwater by natural attenuation as a result of the thickness of the unsaturated zone, high silt content and low permeability. Thirty one elements were determined in the soil samples. The relative abundance of the major and significant trace elements followed the order Al > Fe > K > Mg > Ca > Ti > Na > S > P and V > Mn > Cr > Ba > Sr > Cu > Zn > Pb > Zr > Ni > Sc > Y > Co > Mo respectively. There was a general trend of decrease in metals concentration as the depth of sampling increases. Result of geo-accumulation index showed that the soil samples were practically uncontaminated with Mn, Ni, Zn, Ba, Cr, Sc, Co, Sr, Cu, Zr and Y, practically to moderately contaminated with Pb and V and was moderately contaminated with Mo. Other contamination assessment showed that the soil fall within low contamination factor with all the trace elements except with Pb which falls within moderately contamination.