Physicochemical properties and health risk assessment of selected heavy metals from soil and borehole water in Ifite-Awka, Anambra State, Nigeria

Abstract

Urbanization and industrialization's influence on heavy metal contamination in soil and surface/groundwater resources warrant ongoing attention to protect public health and the environment, especially in Nigeria. Soil samples from different depths (0–10 cm, 15–25 cm, 25–40 cm) and borehole water samples were studied for physicochemical properties and heavy metal content. The result showed that borehole water pH ranged from 5.6 to 6.8, while soil pH ranged from 5.0 to 7.5 which is below WHO limits of 6.5–8.5. Other soil properties such as soil organic matter, cationic exchange capacity, and heavy metals (zinc (Zn), arsenic (As), lead (Pb) and chromium (Cr) were assessed for fertility and pollution indicators. The concentrations of Zn, Pb and Cr were within WHO standards, but As in Sample C exceeded the limits. Heavy metals concentration order in soil was Zn > Cr > As > Pb. Pearson correlations (r) showed positive and negative relationship between variances in soil and water samples ranging − 0.17–0.99 with diverse chemical interactions across all variables analysed. Risk assessment showed average daily intake dominated through ingestion, with low risks through dermal contact. Hazard quotient and index values for all metals were below one (1), indicating minimal non-carcinogenic risks for adults and children via different pathways (inhalation, ingestion, and dermal pathways). However, cancer risk slightly exceeded USEPA levels, especially for children due to prolonged soil exposure. The analysis further revealed that children are more at risk compared to adults from soil exposure (ingestion and dermal) over a long period. The study highlights the importance of continuous monitoring and environmental regulations to ensure sustainability.