Trace metal contamination and health risk assessment in irrigated soils: seasonal dynamics and multivariate insights from a tropical ecosystem

Context Trace metal contamination in soils, arising from both natural and anthropogenic sources such as industrial wastewater irrigation, poses significant ecological and human health risks through biomagnification. Aims This study aims to assess seasonal variations, contamination levels, ecological risk, and health impacts of trace metals (Cd, Cr, Ni, Cu, Zn) in soils using statistical, geostatistical, and human health risk assessment approaches for both adults and children. Methods This study assessed trace metal accumulation in soils irrigated with wastewater and groundwater by collecting seasonal soil samples. Metal concentrations were determined using atomic absorption spectrophotometry, and contamination sources were characterised through statistical analyses. Key results There were significantly higher concentrations of cadmium (Cd), chromium (Cr), nickel (Ni), copper (Cu) and zinc (Zn) in wastewater-irrigated soil (1.93, 31.5, 40.1, 35.46 and 58.65 μg/g) compared to groundwater-irrigated soil (1.78, 11.93, 12.36, 12.06 and 21.51 μg/g, respectively). Seasonal variation analysis indicated elevated Cr, Ni, Cu and Zn levels during the pre-monsoon period, but not Cd. Ecological risk indices, including contamination factor and the geo-accumulation index, identified Cd as the primary contributor to moderate soil contamination. Non-carcinogenic risks were mainly associated with ingestion, particularly affecting children, while inhalation posed no significant carcinogenic threats (Cd, 1.14 × 10−7; Cr, 1.17 × 10−5; Ni, 2.98 × 10−7) to the local population. Correlation analysis, hierarchical cluster analysis and principal component analysis were employed to elucidate inter-metal relationships, identify pollution patterns and trace contamination sources, offering comprehensive insights into trace metal accumulation in irrigated soils. Conclusion Overall, the findings demonstrate that wastewater irrigation, coupled with fertiliser and pesticide use, poses considerable risks to environmental quality and public health. Implications The results underscore the urgent need for sustainable remediation measures, safer irrigation alternatives and continuous monitoring to reduce contamination and protect ecosystems and communities.