Evaluation of pollution indices in Gold Mining communities in the Central Region of Ghana

Abstract

The impact of artisanal small-scale gold mining (galamsey) is of global concern due to its threat to soil, water resources, food production and human health. For this reason, pollution indices of heavy metals in soils at the mining communities of Twifu Ati-Mokwaa District in the Central Region of Ghana where illegal mining is gaining notoriety were evaluated. An agricultural soil auger was used to collect 27 samples to a depth of 20 cm. Physicochemical properties including soil organic matter, moisture, pH, soluble salts, electrical conductivity and ash were determined. The concentrations of As, Cd, Hg and Pb were determined with Agilent AA 240 and AF 70 Atomic Absorption Spectrophotometer. Cadmium was not detected in any of the soils. Concentrations of Pb (0.62 - 12.7mg/kg) were all below pre-industrial values and FAO/WHO guidelines. Levels of As (3.64 - 39.84mg/kg) varied greatly with nine sites recording concentrations above the FAO/WHO permissible limit. Concentrations of Hg (0.02 – 6.47 mg/kg) were also high with eighteen of the twenty-seven site levels above FAO/WHO permissible limit. The observed differences in means from each site were statistically significant (p < 0.05) in all three communities. Degree of contamination, geoaccumulation and ecological risk indices were high for Hg and As but low for Pb. The PINemerow and PLI values however signalled slight pollution to severe pollution at 85.2% of the sample sites. The implication of these findings is that artisanal gold mining should be discouraged and lands should be thoroughly remediated before cultivated for agricultural production.

Keywords

• artisanal small-scale gold minig
• contamination degree
• geoaccumulation index
• ecological risk factor
• pollution load index