Variations in Concentrations of Arsenic and Other Potentially Toxic Elements in Mine and Paddy Soils and Irrigation Waters from Southern Ghana

Abstract

This study was undertaken to ascertain the impact of gold mining on soil and water chemistry as well as on rice grain quality. Samples collected from both gold mining and non-gold mining regions of southern Ghana were analysed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of arsenic and other potentially toxic elements (PTEs). Significant differences were observed between sites with respect to soil As, Co, Cu, Pb and Zn concentrations. Paddy soils from the Anum Valley Irrigation Project site, located close to the old Konongo Gold Mine in the Ashanti region, contained up to 103 mg arsenic/kg. Although higher arsenic concentrations were recorded in mine soils from Bogosu in the western region, paddy soil samples from this region contained relatively low concentrations of arsenic, suggesting that the contribution of gold mining to soil contamination is a function of distance from the point source of contaminants. Transfer of soil arsenic to rice grain was significantly higher in gold mining regions compared to non-gold mining regions. At the Anum Valley Irrigation Project site, where surface waters containing 144 μg arsenic/l were used for paddy irrigation, rice grain arsenic concentration reached 0.59 mg/kg, indicating a potential risk of arsenic transfer to the food chain.