ASSESSMENT OF HEAVY METAL CONCENTRATIONS OF SOIL AND WATER IN THE VICINITY OF GURMANA GOLD MINING SITE, NIGER STATE, NIGERIA

Abstract

The release of mining waste containing different toxic heavy metals have reached an alarming rate that deserves prompt attention. Hence, the purpose of this study was to determine extent of contamination of soil and water from Gurmana Gold Mining Site. A total of seventeen (17) samples comprising twelve (12) soil and five (5) water samples were collected. The samples were digested using nitric-perchloric acid mixture (3:1) and analysed for selected heavy metals (Cd, Cu, Cr, Pb, Mn, Ni and Zn) using an Atomic Absorption Spectrophotometer. The results revealed that the soil pH, organic matter and cation exchange capacity have values in the range of 6.37 – 6.80, 1.74 – 1.95% and 6.88 – 8.11 cmol/kg respectively. While pH of the water samples has a range 6.74 – 7.69 is lower than 6.5 – 8.5 (USEPA recommended standard). The heavy metal contents: Cu, Fe, Mn, Ni, Pb and Zn in soil samples had concentrations that ranged from 6.38 mg/kg, 72.4522.78 to 457.53164.71 mg/kg, 11.054.95 to 27.9320.39 mg/kg, 2.48 1.31 to 3.893.35 mg/kg, 1.381.38 to 3.343.34 mg/kg and 15.5715.57 to 26.60 26.60 mg/kg respectively. These concentrations were within the FAO/WHO maximum permissible limits of 100 mg/kg, 50,000 mg/kg, 2000 mg/kg, 50 mg/kg, 100 mg/kg and 200 mg/kg respectively except cadmium which was not detected all through the sampling sites. The water samples from well, spring, borehole and river from Gurmana revealed the presence of Cu, Fe, Mn, Ni and Zn in the range of 0.05 – 0.11 mg/dm3, 1.93 – 48.78 mg/dm3, 0.11 – 1.15 mg/dm3, 0.02 – 0.07 mg/dm3, and 0.02 – 0.07 mg/dm3 respectively. Cd and Pb were below detection limit throughout in the water samples, while Fe was below detection limit in river and borehole samples and Zn was also below detection limit in the spring, borehole and river water samples. The contamination factor of soil samples ranged from very slightly contamination to slightly contamination, while that of water samples ranged from low contamination to a very high contamination level. The contamination of soil and water by these heavy metals could be attributed to mining activities in the area. The levels of potentially toxic heavy metals in soil and water should be assessed and monitored regularly in order to forestall the impending health risk associated with heavy metals arising from illegal mining activities.