Assessment of Physicochemical Properties and Heavy Metal Contamination of Surface Waters in Enugu State, Nigeria

This study assessed the physicochemical properties and the extent of heavy metal contamination of surface waters across selected locations in Enugu State, Nigeria, with a view to establishing their suitability for domestic and agricultural use and the public health risks associated with their consumption. Surface water samples were collected from twelve sampling stations distributed across the three senatorial zones of the State and analyzed for physicochemical parameters including pH, electrical conductivity, total dissolved solids (TDS), turbidity, dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrate and phosphate, as well as for the heavy metals lead (Pb), cadmium (Cd), chromium (Cr), iron (Fe), zinc (Zn) and copper (Cu). Standard analytical procedures recommended by the American Public Health Association were adopted, and concentrations were compared with the permissible limits of the Nigerian Standard for Drinking Water Quality and the World Health Organization. Results revealed that while parameters such as pH (6.1–7.4), TDS and conductivity largely fell within permissible limits, turbidity, BOD and nitrate at several urban and mining-influenced stations exceeded regulatory thresholds. Heavy metal analysis showed that lead (mean 0.061 mg/L) and cadmium (mean 0.009 mg/L) exceeded both NSDWQ and WHO permissible limits at most stations, while iron and chromium were elevated at coal-mining and industrial sites. Performance percentage analysis indicated that only 41.7% of stations met the acceptable standard for combined heavy metal load. Pearson correlation analysis revealed strong positive relationships between conductivity and TDS (r = 0.91) and between turbidity and heavy metal load (r = 0.78), while regression analysis confirmed that anthropogenic activity significantly predicted heavy metal concentration (p < 0.05). The study concludes that surface waters in Enugu State are moderately to heavily impacted by anthropogenic contamination, particularly from coal mining, urban runoff and indiscriminate waste disposal, and recommends sustained monitoring, enforcement of effluent standards and community sensitization