ASSESSMENT OF HEAVYMETALS IN OLD MINING SITES IN JOS SOUTH LOCAL GOVERNMENT AREA OF PLATEAU STATENIGERIA.

Abstract

The purpose of this study was to assess the concentration of some heavy metals:namely Cu, Cd, Pb, Zn and Cr in abandoned tin mined soils around Du and Zawan, Jos south local government area, Plateau state. A total of 30 soil samples were collected randomly from the sites at a depth of 0 to 15cm and two common plants grown (maize and beans) were collected for this study. Physicochemical properties of the soil samples were determined. The soil samples were subjected to sequential extraction and total metal determination and the extract for the heavy metals was analyzed using Atomic AbsorptionSpectrophotometer. The statistical analyses were conducted using one way analysis of variance. The mean pH and electrode potential ranged from 5.33 to 6.14 and 49.7 to 82.7 respectively, while the electrical conductivity and organic matter ranged from 33.7 to 94.3 and 2.04 to 3.81 respectively. The mean concentration levels of heavy metals ranged from Zn > Cu > Cr >Pb> Cd for total metal determination and it was observed that the mining sites showed more concentration of heavy metals than the control. The results obtained for sequential extraction followed the same trend for copper, chromium and lead which showed higher concentrations at the residual fraction while cadmium and zinc had more concentration at the non-residual fraction. The pollution potentials for all the metals were calculated and was observed that cadmium for both Du and Zawan mining sites were higher than the maximum permissible limit allowed by World Health Organization (WHO).While chromium, lead, zinc and copper followed same trend of low contamination. The analysis of the food samples from the 3 sites had low concentrations of metals and are good for consumption since the metals are below WHO maximum permissible limits. But there is a gradual build up of cadmium in the abandoned mined sites and the consumption of food grown on these soils may harm the consumers.