Assessment of Surface and Groundwater Quality in Gussoro Gold Mining Site, Niger State, North-Central Nigeria

Abstract

The water quality in Gussoro area of Niger State, North-central Nigeria was investigated in this study. Gussoro is located at the downstream of River Shiroro where the community carries out farming, artisanal mining and fishing activities. Field geological mapping of the area revealed that schist is the major lithological unit in the area. The schist was intruded by medium grained granite on the north-eastern part of the study area. The results of the laboratory analysis of both the surface and groundwater samples indicate that the pH of the water in some locations is slightly acidic. The concentrations of all the analyzed major cations (sodium, calcium, magnesium and potassium) as well as major anions (sulphate, chloride, bicarbonate, carbonate and nitrate) are below World Health Organization maximum permissible limits However, in some locations, the concentrations of fluoride, iron, nickel, manganese and arsenic were higher than the recommended maximum permissible limits. Their enrichment in the surface and groundwater system in the area may be attributed to artisanal mining and farming activities in the area. The slightly acidic nature of the water in the area enhances chemical weathering as well as rock dissolution process, thereby enriching the water with these elements. Presently, there are no cases of dental fluorosis in the study area, despite the high concentration of fluoride in some locations. High concentration of fluoride in the water can be attributed to weathering of fluoride bearing mineral such as apatite and fluorite in granitic rock located at north-eastern part of the study area. Nickel, manganese, lead and arsenic are pathfinder elements to gold and are often discarded as gangue into the surrounding soils and surface water This partly explains the concentrations of these metals are higher in surface water compared to groundwater High concentration of iron in the water is due to the oxidation and weathering of pyrite that is associated with the gold mineralization in the area. Water types in the area from Durov and Piper diagrams revealed Na Ca/CI+50, facies. Gibbs diagram also indicated that weathering is the major hydrogeochemical processes controlling the discharge of ions in water sources in the area. Water in areas with anomalous concentration of fluoride and heavy metals should be treated before use.