Risk assessment of potentially toxic elements in water, sediment, aquatic mussels, and edible crops from a gold-mining-stressed river in Northern Nigeria

Abstract

The degradation of aquatic ecosystems by Potentially Toxic Elements (PTEs) arising from artisanal gold mining is a major global ecotoxicological concern. The health and ecological risk assessment of key PTEs such as cadmium (Cd), Cr(VI) (Cr), copper (Cu), lead (Pb), and nickel (Ni) in water, sediment, bivalves, cassava, and spinach from the Chanchaga River, a vital resource for gold prospecting, irrigation, and domestic purposes, was investigated. Water and biota samples were collected according to standard procedures, and PTE concentrations were quantified by Atomic Absorption Spectrophotometry. Spatial analysis revealed significant (p < 0.05) variation in PTE concentrations across sampling stations, with all metals, except Cu, exceeding the WHO guideline values in water by approximately 10-fold. The concentration of PTEs in sediment was in the order, Station 4 > Station 3 > Station 1 > Station 2 > Station 5. The distribution of PTEs in the biota was in the order Cr > Pb > Ni > Cd > Cu, with BAFs > 1 for all metals, indicating efficient mobilization from environmental media into edible and aquatic organisms. Pollution indices classified most sites as moderately to highly contaminated. Elevated levels of PTEs were strongly associated with gold mining activities. Human health risk assessment showed that oral exposure through drinking water and consumption of local crops and bivalves may pose significant non-carcinogenic and carcinogenic risks to both adults and children. There is a need for stringent regulation of illegal gold mining, provision of safe alternative water sources, and reduced consumption of locally contaminated produce.