The study determined the following heavy metals: cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) concentrations in surface water and in fish pond (water, sediments and farmed fish (Clarias gariepinus)) from a fish farm cluster with the view of assessing its pollution level and associated human health exposure risk to these heavy metals through fish consumption. Samples were digested with aqua regia and metal concentrations were determined with an atomic absorption spectrophotometer equipped with an air acetylene flame. Mean concentrations of the heavy metals (ppm) in surface and pond water ranged as follows: cadmium (below detection limit (bdl): 0.298); chromium (bdl: 0.257); copper (bdl: 0.067); manganese (bdl: 0.163); lead (bdl: 0.736) and zinc (bdl: 0.078) while in sediment, the ranges (mg/kg dry weight) were as follows: cadmium (1.156–3.329); chromium (9.439–14.373); copper (26.710–121.819); manganese (3.143–37.202); lead (0.340–1.537) and zinc (87.681–371.060). The mean concentrations of the metals in surface water were significantly different (p < 0.05) from those in sediment in all the sampling sites. The mean metal concentrations (mg/kg dry weight) in C. gariepnus were in the following ranges: cadmium (0.733–1.405); chromium (0.593–1.692); copper (175.882–245.321); manganese (bdl: 3.326); lead (0.221–0.263) and zinc (248.191–292.333). Some of the heavy metal concentrations obtained in water, sediment and catfish analyzed were above the permissible limit set by some National (DPR) and International organisations (WHO, FEPA and FAO). The pollution studies showed that lead, cadmium and chromium contaminated the surface water samples. Sediment from all sites showed low to considerable contamination by the heavy metals. The human exposure risk assessment of the metals showed that the total hazard index was less than one which indicates no probable adverse health effect from the consumption of fish from the ponds, although this case is different for Pb since there is no estimation of oral reference dose (RfDo) for lead according to EPA.

Assessing water quality is necessary to ascertain its viability for domestic, industrial, and agricultural purposes. A total of 48 water samples were, respectively, drawn from the Rivers Karawa and Iyiaji located in Ezeagu and Uzo-uwani which are typical rural areas in Enugu State, Nigeria. These samples were taken in two seasons (early rainy season and late dry season). Physicochemical properties were determined using standard methods. The scaling and corrosivity potentials of the water were evaluated using the Larson-Skold index, aggressive index, Puckorius scaling index, and Ryznar stability index models. Additionally, seven irrigation evaluation criteria, as well as spatial distribution maps, were used to determine the suitability of the river waters for irrigation purposes and to interpolate the spatial distribution of the river water quality parameters. Major ion chemistry was used in the assessments. The physicochemical properties of river waters fell within the recommended standard values. However, NO₃⁻ greatly exceeded the recommended range in both rivers. The cations and anions from River Karawa were Ca²⁺ > Mg²⁺ > K⁺ > Na⁺ and NO₃⁻ > Cl⁻ > SO₄²⁻ > HCO₃⁻ > CO₃⁻ > PO₄⁻, while those from River Iyiaji were Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ and Cl⁻ > SO₄²⁻ >NO₃⁻ > PO₄⁻ > HCO₃⁻ > CO₃⁻. A piper plot showed the predominance of Ca²⁺ and Mg⁺, as well as SO₄²⁻ and Cl⁻, in both rivers. The seven irrigation assessment indices indicated that the water of the Rivers Karawa and Iyiaji is suitable for irrigation purposes. In addition, the scaling and corrosivity models predicted that the river waters have high scaling and corrosivity potentials. Specifically, while the aggressive index suggested that it is severely corrosive, the Langelier saturation index suggested that the water from both rivers is supersaturated and, thus, has potential to scale.