Chemical Composition of Rainwater over a Mining Area in Ghana

A comprehensive study on the chemical composition of rainwater was carried out in Obuasi, a gold mining town in Ghana. Rainwater samples were analyzed for major ions (Ca super(2+), Mg super(2+), K super(+), Na super(+), NH super(+) sub(4), Cl super(-), N0 super(-) sub(3) and SO super(2) sub(4) super(-)) and trace metals (Fe, Al, Zn, Pb, Cr, and Cd). The rainwater was typically acidic with a mean pH of 4.76 plus or minus 0.47, which ranged from 4.0 to 5.6. The low pH found in the water suggests that the concentration of the alkaline particles in the rainwater were not high enough to neutralize acidic species present. SO super(2) sub(4) super(") and Cl" were the main anions, while Ca super(2+) and K super(+)were the main cations. Concentrations of trace metals in this study were compared with those of other studies conducted at different sites in the world. The result of this study generally suggests that rainwater chemistry in the area is strongly influenced by local anthropogenic sources (mining). The pollutants in rainwater samples were mainly derived from mining activities. Concentrations of Pb in all the samples were above the WHO permissible limit of 0.01 mg/L for drinking water.