ABSTRACT
Soils and groundwater qualities around dumpsites have been observed overtime to have significantly deteriorated. To this end, soils, groundwater, river water and leachate samples around Upper Ekehuan (Asoro) dumpsite in Ovia North Local Government Area, Benin, were collected in order to investigate the impact of the dumpsite on soils and groundwater. A total of fourty-two(42) samples consisting of thirty six (36) soils/sediments, three(3) groundwater, two(2) river water samples (upstream and downstream) and one(1) leachate sample were analyzed using Atomic Absorption Spectrophotometer(AAS) PG550model with air acetylene flame. The results revealed that the pH values of soil samples range between 6.19-9.21 indicating that the soils are slightly acidic to slightly alkaline while groundwater samples range between 5.08-5.58, river water samples have values of 6.52 and 6.55 and leachate has a value of 6.82, all slightly acidic. The results of soil samples show that the concentration of Cd (1.74mg/kg), Cr (6.31mg/kg), Pb (3.32mg/kg), Mn (15.54mg/kg) and Ni(3.39mg/kg) were much lower than regulatory standards(USEPA). The average values for Zn, Cu, and Pb are lower than the US Environmental Protection Agency (USEPA) for metal but average values for Cd is a little higher than that of US-EPA.The average values for Zn, Pb, Cu, Cd, Ni and Cr are lower than the severe effect range of the New York Sediment Criteria and the high effect range (ISQG-high) of the Sediment Quality Criteria. The soils, with 30-49% and 50-69% sand fractions are considered to have low to intermediate leaching potentials within the probed depth range. Hazard assessment of the heavy metals showed that the order of occurrence followed the sequence of Fe ˃ Cu ˃ Zn ˃ Cr ˃ Pb Ni ˃ Cd.
Furthermore, the application of statistical analysis [Correlation and Analysis of Variance (ANOVA)], the correlation of heavy metals with pH indicates that the pH has no effect on the soil samples because the coefficients are negative but there is moderate correlation of pH with the water samples, this means that the acidity or alkalinity has effect on the water samples.The ANOVA analysis shows the F factor to be 0.12.This value is greater than 0.05; and shows that there is a significant difference between the control location and the dumpsite locations.
Heavy metals such as Ni, Cd, Cr, Mn, Cl-, Fe and Pb as well as turbidity in the leachate results are observed to have concentrations above the World Health Organization’s (WHO) and Nigeria Standard for Drinking Water Quality (NSDWQ) maximum permissible limits. Groundwater analytical results have values for Fe and Cl- to be above regulatory standard (WHO and NSDWQ); and BH2 to have higher value for Ni. River water have above standards values for Ni and Cl-.
