Assessment of Metal Contamination and Human Health Risk in the Buffalo River Estuary, Eastern Cape, South Africa

Metal contamination in estuarine environments poses environmental and public health concerns, particularly where surface waters support domestic and subsistence uses. This study assessed the seasonal distribution, controlling mechanisms, and non-carcinogenic health risks of selected metals (Mg, Al, Ba, Fe, Mn, and Zn) in the Buffalo River Estuary, Eastern Cape, South Africa. Water samples were collected from 11 stations during wet and dry seasons and analyzed using standard methods. Descriptive statistics, Pearson's correlation analysis, and principal component analysis (PCA) were applied to evaluate metal distribution, inter-element relationships, and dominant controlling processes. Marked seasonal variability was observed, with higher concentrations of Al (97-1708 μg/L), Ba (7.4-29 μg/L), Fe (54-1751 μg/L), Mn (4-116 μg/L), and Zn (4-23 μg/L) during the wet season, while Mg concentrations were elevated in the dry season (10686-851 382 μg/L) relative to the wet season (1056-1313 μg/L). PCA indicated that wet-season metal dynamics were governed by lithogenic and hydrological processes linked to runoff and suspended sediments, whereas dry-season variability reflected sedimentary geochemical controls, redox processes, conservative mixing, and secondary anthropogenic inputs. Non-carcinogenic health risk assessment for Al, Ba, Fe, Mn, and Zn showed Mn as the largest contributor to risk, although cumulative hazard indices for adults (2.19 × 10^-2-1.39 × 10^-1) and children (8.10 × 10^-2-5.01 × 10^-1) remained below unity, indicating low health risk. These findings highlight the dominance of seasonal geochemical processes, providing essential baseline data for water-quality management, and underscore the need for continued monitoring to support effective water-resource management.