Assessment of some selected heavy metals in water samples at kombolcha town, south wollo zone, Ethiopia

Water quality in rapidly industrializing towns is increasingly threatened by heavy metal contamination, yet updated site-specific quantitative evidence on metal burdens and their seasonal/spatial variability needed for targeted wastewater management remains limited. In Kombolcha town, Ethiopia, where many chemical-using industries discharge poorly treated wastewater into nearby river systems, this study addresses that research gap. Heavy metals (Pb, Cd, Ni, and Cu) were quantified in the Luyele, Worka, and Borkena river systems and in the Kombolcha Industrial Park across four seasons (August, November, February, and May). Triplicate acid-cleaned samples were collected from selected upstream-to-downstream sites. Physico-chemical parameters (including pH and electrical conductivity) were measured in situ, while dissolved and total heavy metals were determined in the laboratory by atomic absorption spectroscopy after digestion and optimization of HNO3:HCl ratios. All sites showed detectable heavy metals. Mean Pb concentrations ranged from 0.034±0.006 to 0.091±0.035 mg/L and exceeded the WHO permissible limit for drinking water (0.01 mg/L). Cd ranged from 0.020±0.005 to 0.041±0.005 mg/L and also exceeded the WHO drinking water guideline (0.003 mg/L). Ni (0.075±0.011–0.098±0.012 mg/L) and Cu (0.697±0.126–1.385±0.091 mg/L) were detected throughout; Cu remained below the WHO drinking water limit (2.0 mg/L). Electrical conductivity and metal levels generally increased from upstream to downstream, supporting an industrial discharge influence. Method accuracy was supported by 90–98% recovery. Practically, the results provide baseline data to prioritize the mitigation of Pb and Cd contamination and facilitates the implementation of more rigorous industrial effluent monitoring.