Assessment Of Heavy Metal Toxicity Load (HMTL) For Water Quality Improvement: A Case Study of NVUNA River In ITUKU Community, Enugu State, Nigeria

Abstract

Water pollution from human activities remains a global concern, predominantly due to toxic heavy metals that pose significant health risks. This study assessed the heavy metal toxicity load (HMTL) in water and sediment from the Nvuna River in Ituku Ozalla, Enugu State, Nigeria. Six water samples were analyzed for physicochemical properties and four heavy metals using atomic absorption spectrophotometry. The HMTL and Metal Index (MI) were calculated to evaluate contamination levels. Results showed water pH ranged from 7.23 to 8.03, while sediment pH ranged from 7.50 to 8.10, indicating alkaline conditions. Conductivity values were 31.02–36.84 μS/cm in water and 30.37–37.49 μS/cm in sediment. Turbidity, total solids, nitrate, and sulfate levels were within WHO limits. Heavy metal analysis revealed no detectable levels of lead (Pb), cadmium (Cd), or arsenic (As). However, mercury (Hg) levels in water (0.001–0.002 mg/L) exceeded the WHO permissible limit (0.001 mg/L). The MI values were 1.5 for water and 29 for sediment, while HMTL ranged from 1.455 to 119.31 mg/L, with an average of 43.165 mg/L. The findings highlight severe mercury contamination, with 88% of the heavy metal load needing removal for water to be safe for consumption. Elevated MI and HMTL values indicate significant risks to drinking water safety and aquatic ecosystems, underscoring the urgent need for remediation to restore water quality in the study area.