Contamination Status of Residential and Farmland Surface Soils Within the Sunyani Municipality of Ghana

Exposure to heavy metals poses serious human health and ecological threats, especially in developing countries where ecological risk assessment and remediation are often ignored. While many studies have reported heavy metal toxicities in rapidly urbanizing cities with increased anthropogenic activities, limited information exists on metal toxicities and their ecological risks in soils within the Sunyani Municipality. Top soils were sampled from residential and farmland surface soils and analyzed for the concentration and potential risks for nine heavy metals within Sunyani Municipality. Apart from As and Mn, the two study sites generally recorded elevated levels of all metals than the pristine soil samples from the University of Energy and Natural Resources botanical garden. Levels of chromium, copper, lead, and zinc were however marginally higher in residential surface soils than in the farmlands. The soil contamination factor and geoaccumulation index both revealed moderate As, Hg, and Mn contamination at the two study locations. Furthermore, the soil enrichment factor showed significant enrichment for arsenic and moderate enrichment for cadmium in residential soils, while the farmland soils revealed moderate enrichment of As, Hg, and Mn. The potential ecological risk indices also showed considerable risk at both study locations, while the pollution load index revealed higher cumulative pollution in residential areas (PLI = 0.48) compared to the farmland surface soil (PLI = 0.40). The study therefore recommends the regulation of human activities and the use of chemicals that are possible sources of metal contamination to maintain the metals’ baseline levels in the soil, and reduce their health and environmental impacts.