Utility of pollution indices in assessment of soil quality around Madaga gold mining site, Niger state, North-central Nigeria
The quality of soil in the vicinity of Madaka mining sites were investigated in this study using Environmental Pollution Indices. Geological mapping of the study area indicated that the area was dominated by schist and granite. The static water level measurement revealed a westward groundwater flow direction which also coincides with the regional structural trend of the area. Laboratory analyses of soil and stream sediment were carried out in National Geosciences Research Laboratory Kaduna. The results of the soil analyses revealed high concentrations of mercury, cadmium, lead and arsenic. The results of the laboratory analysis were further elucidated using pollution indices such as geo-accumulation index, contamination factor, degree of contamination, elemental contamination index and metal pollution index. These environmental indices revealed that the soil is seriously polluted with mercury, cadmium and lead, moderately polluted with arsenic, lightly polluted with iron and copper and very lightly polluted with manganese, zinc, nickel and cobalt in the order of: Hg > Cd >Pb> As > Fe > Cu > Mn > Zn > Ni > Co. The mean concentrations of the first four metals (Hg, Cd, Pb and As) exceeds their average crustal abundance, which is an indication of possible pollution. The concentrations map of the analyzed heavy metals indicated a westward decrease in concentration away from the mine sites. This was in agreement with the flow direction and the possible reduction in pollution intensity away from the mine sites could be attributed to the natural attenuation mechanism of soil in the course of groundwater migration as well as hydrogeological attributes of the area. The study recommends that the miners be grouped into association and trained on modern mining techniques that are environmental friendly. The polluted soils in the area should be remediated and proper sensitization on the dangers associated with artisanal mining should be carried out in the area. Periodic monitoring of the soil quality in the area is advocated.
Keywords: Utility, Environmental Pollution Indices, Impact, Artisanal Gold Mining, Madaga, Niger State, North-central Nigeria