Comparative assessment of heavy metal accumulation and associated ecological and health risks in citrus orchards under canal and domestic wastewater irrigation

Sargodha is popularly known as California of Pakistan because of its renowned production of superior quality citrus cultivars. However, the increasing reliance on domestic wastewater for irrigation in this region has raised serious concerns regarding the accumulation of hazardous metals in soil and edible fruit tissues. This may pose a significant risk to food safety and human health. In this study, a field-based comparative sampling strategy was adopted, where irrigation water, soil, and citrus fruit samples were obtained from orchards with canal water irrigation (CW-I) and domestic wastewater irrigation (DWW-II). Samples of water, soil, and fruits were analysed through atomic absorption spectrophotometry to evaluate the accumulation of selected heavy metals in irrigation water, soil, and edible parts of three citrus species grown under CW-I and DWW-II irrigation systems. Zn concentrations ranged from 13.31–51.67 mg L −1 in water, 44–71 mg kg −1 in soil, and 1.08–1.58 mg kg −1 in fruits. Cr levels varied between 1.86–11.66 mg L −1 in water, 9.67–22.70 mg kg −1 in soil, and 0.011–0.10 mg kg −1 in fruits. Ecological risk assessment indicated higher metal accumulation in citrus fruits irrigated with DWW-II compared to CW-I, as indicated by elevated contamination factor (CF) and enrichment factor (EF), with Zn consistently showing the lowest contribution. The pollution load index (PLI) values exceeded 1 under domestic wastewater irrigation (1.53–1.65), suggesting moderate pollution. The estimated daily intake (EDI) values were higher for all metals under domestic wastewater irrigation, particularly for Fe (0.122 mg kg −1 day −1 ) and Zn (0.0604 mg kg −1 day −1 ), yet remained below permissible limits. Health risk assessment revealed that THQ values for all studied metals remained within permissible limits, indicating no significant non-carcinogenic risk associated with the consumption of these citrus fruits. The findings demonstrate that domestic wastewater irrigation significantly increased metal concentrations in soil and fruits. These results highlight the importance of continuous monitoring and the implementation of sustainable irrigation practices to minimize long-term health risks associated with wastewater use in agriculture.