PRELIMINARY STUDIES ON THE DISTRIBUTION CHARACTERISTICS OF POTENTIALLY TOXIC METALS IN SOILS AROUND A GOLD MINING SITE IN IJERO, EKITI STATE, NIGERIA

Abstract

Metal pollution in soils arising from mining activities has become a growing
concern especially in developing countries like Nigeria. Illegal mining of solid
minerals pervades the entire country leaving behind their deleterious effects on the
environment. This research focused on the preliminary studies on the distribution
characteristics of nine potentially toxic metals in soils around a mining site in Ekiti
State, Nigeria. Thirteen (13) soil samples were randomly collected in and around
the vicinity of the mining site and a control sample at a farther distance from the
mining site. The soil samples were air dried, sieved through a 63 mm mesh sieve
and 1g of each of the samples was digested using a microwave digester for two
hours. The potentially toxic metal concentration was determined using an Agilent
7700s Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The
concentration of the metals analysed in the samples were within the following
ranges; As (0.20 to 83.49 mg/kg), Cd (0.03 to 0.39mg/kg), Cr (0.65 to 38.16 mg/kg),
Cu (3.11 to 11.46 mg/kg), Fe (2.46 to 137.63 mg/kg), Mn (45.88 to 557.20 mg/kg),
Ni (0.30 to 10.84 mg/kg), Pb (2.83 to 20.28 mg/kg) and Zn (5.68 to 24.16 mg/kg).
Concentrations of As and Cd were above the permissible levels in the environment.
The calculated pollution index (Pi) values for As (location 2) and Cd (location 5)
under the study exceeded 1 confirming that the soils are highly polluted particularly
with As and Cd. Therefore, it is recommended that farmers should not grow
agricultural foods such as edible vegetables, rice and potato in these soils unless the
soils have been treated and remediated. In addition, mining activities had impacted
negatively on the surrounding environment and the results of this analysis suggests
that the metal concentrations of the sites resulted from mining activities are
expected to be higher in the nearest future due to bioaccumulation and as such, the
activities should be regulated and arrested.