Seasonal assessment of heavy metal contamination, pollution indices, and human health risks in dumpsite soils of Abakpa bridge, Enugu State, Nigeria

Abstract

This study assessed heavy metal contamination and associated ecological and human health risks at a municipal dumpsite using established pollution indices and risk models. Soil samples collected from three stations (A–C) during rainy and dry seasons were analyzed for Cd, As, Fe, Zn, Cr, Pb, and Hg. Results showed clear seasonal and spatial variations, with higher concentrations generally recorded in the dry season. Cadmium exhibited the highest contamination, with CF values ranging from 12.74–23.40 and EF values of 191.6–211.6, indicating very high anthropogenic enrichment. The Igeo values for Cd (3.09–3.96) classified the site as strongly polluted, while Pb showed moderate pollution (Igeo: 0.60–1.65). Other metals remained largely within unpolluted categories (Igeo ≤ 0). The degree of contamination (Cd) ranged from 16.74–31.78, indicating considerable contamination, while PLI values (0.51–1.01) suggested moderate overall pollution with localized deterioration. Ecological risk assessment identified Cd as the major contributor to risk, reflecting its high toxicity and elevated concentration. Human health risk assessment revealed ingestion as the dominant exposure pathway. The total hazard index (THI) for children (3.97 × 10²) was significantly higher than for adults (4.25 × 10¹), exceeding the safety threshold (THI > 1).  Arsenic and cadmium contributed most to risk, with ingestion HQ values of 205.3 and 70.0, respectively, for children. Dermal exposure contributed moderately, while inhalation was negligible (10⁻³).Overall, the dumpsite poses significant ecological and human health risks, necessitating improved waste management, environmental monitoring, and remediation strategies.