Environmental Contamination and Health Risk Assessment of Heavy Metals in the Stream Sediments of Oued Kasseb (Northerwest of Tunisia) in the Vicinity of Abandoned Pb-Zn Mine

Mining activities have a positive impact on the global economy by increasing the socio-economic impact of the country's economic growth. However, they pose a high environmental risk of damaging sediments, and aquatic ecosystems by accumulating potentially toxic elements. Located in northern Tunisia, Oued Kasseb is one of the outlets of the Medjerda River, Tunisia's main watercourse and a major source of irrigation and drinking water. Oued Kasseb is the nearest watercourse to the Pb-Zn mining district of Djebel Hallouf-Sidi Bouaouane, a century-old mine (1890-1986). This study focuses on evaluating the spatial distribution of heavy metals (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn)), their degree of contamination, using pollution indices, and on assessing the ecological and human health risks posed in the Oued Kasseb study area. The obtained heavy metal concentrations were in the following order: Pb > Zn > As > Cr > Ni > Cu > Cd. The spatial distribution shows that relatively high concentrations of metals were found in the vicinity of the Pb-Zn abandoned mine. The geoaccumulation index (I geo), the enrichment factor (EF), the contamination factor (CF), and the potential ecological risk index (RI) showed that the sediments are highly contaminated with As, Cd, Pb, and Zn, especially for sites surrounding the mine. The statistical analysis shows that As, Cd, Cu, and Pb are correlated strongly with Zn and appeared in the first component (F1:70.89%). The noncancerogenic risk revealed that As damages the children whereas it is not harmful to the adult group. The abandoned Pb-Zn mines are therefore the main source of heavy metals in the Oued Kasseb, causing serious environmental pollution and posing significant health risks.