Mercury waste from artisanal and small-scale gold mining facilities: a risk to farm ecosystems—a case study of Obuasi, Ghana

Frequent discharge of mercury waste from artisanal and small-scale gold mining (ASGM) facilities into nearby farms may contaminate foodstuffs and the entire farms. High contamination levels may result in ecological risks to the soil, plants, animals, humans, and the entire farm ecosystem. This original research is the first study within the catchment areas that describes the effects of mercury waste on the entire farm ecosystem. In this study, the contamination levels and the associated ecological risks of farmland soils, plantains, and cassavas from farms sited near ASGM facilities in four communities around Obuasi, Ghana, were evaluated using the Hakanson (1980) model. Results showed that all samples except for the edible parts of plantains from Tweapease, Nyamebekyere, and Ahansonyewodea and plantain peels from Nyamebekyere and Ahansonyewodea were contaminated and may pose moderate to very high ecological risks. All farms were also contaminated and may pose considerable to very high ecological risks. The farms at Odumase were the highest contaminated with degree of contamination (Cdeg) above 20, while those at Ahansonyewodea were the least contaminated with Cdeg = 8.1. This meant that farms at Odumase may pose the highest potential ecological risk (Per) to plants, animals, humans, and the entire farm ecosystem since Per > 600, while the farms at Ahansonyewodea may pose the least ecological risks with Per = 324. There is, therefore, the need for strict control of ASGM activities in these study areas to preserve the integrity of the ecosystem.