Impact Assessment of Tin Mining on Heavy Metals Accumulation in the Soils of Bukuru Jos North Central Nigeria

This research was carried out to assess the impact of tin mining on the soils of Bukuru-Jos, North Central Nigeria. The study was conducted in three (3) locations of Bukuru study area namely, Gyel, Rabi and Fwarti. Twelve (12) profile pits were cited, three (3) of which were cited at the mined sites and one (1) at the unmined sites (control) in each location of the study area. A total of sixty (60) soil samples were collected from all the profile pits taken at 0-10 cm, 10 -20 cm, 20 -30 cm, 30 - 40 cm and 40 -50 cm, in 4 replications in each of the three locations of the study area. The result of laboratory analyses revealed eight (8) heavy metals identified at Gyel and Rabi locations, namely, Zn, Pb, Cu, Fe, Mn, Cr, Ni and Cd. At Fwarti location, however, seven (7) of the heavy metals were identified, namely, Zn, Pb, Cu, Fe, Mn, Ni and Cd. Comparism of the mean values of these heavy metals with their respective FAO/WHO critical limits for agricultural soils showed that Gyel location was contaminated with Zn, Pb, Cu, Fe, Mn, Cr and Ni. Rabi location was contaminated with four of the heavy metals identified, namely, Pb, Cu, Fe and Mn, while the abandoned tin mine at Fwarti was contaminated with five (5) of the heavy metals, namely, Pb, Cu, Fe, Mn and Ni. The mean concentrations of the heavy metals identified at both the mined areas and control were above their respective WHO/FAO (2001) critical limits in agricultural soils except for Cd which was below its own critical limit, and Co which was not detected. Therefore, both the mined areas and the control, at least a kilometre away from the mined areas were contaminated with the identified heavy metals except for Cd. Bukuru soils were therefore contaminated with Zn, Pb, Cu, Fe, Mn, Cr, Ni, which occurred in the followingorder; Fegreater than Mn greater than Cr greater than Pb greater than Zn greater than Cu greater thanNi.