Assessment of soil and crop contamination along El-Qalyubia Drain, Egypt, based on contamination indices

Purpose This study aims to investigate the spatial distribution and seasonal dynamics of toxic metals in water, soil and edible crops cultivated near the El-Qalyubia Drain, Egypt. Where irrigation sources may include reused agricultural drainage water. It aims to identify contamination hotspots, assess ecological risks and evaluate the food safety implications of drainage water reuse. Design/methodology/approach Soil, drainage water and edible plant samples were collected from eight sites during summer and winter. Ecological risks were evaluated using the contamination factor, ecological risk factor, potential ecological risk index and pollution load index. Crop contamination was assessed in accordance with the Codex Alimentarius maximum permissible limits for food safety. Findings Drainage water met Egyptian standards; however, certain soils and crops exhibited elevated contamination, particularly with copper, manganese, cadmium and lead. Wheat, turnip and molokheya frequently exceeded Codex limits for cadmium and lead. Copper enrichment was most pronounced in winter (Cf > 40). The ecological risk index indicated low risk in summer (RI = 33.38) but moderate in winter (RI = 173.42). Research limitations/implications The study covered one major drain and two seasons, limiting extrapolation to other systems or longer timescales. Broader multi-drain and multi-year studies across diverse agro-ecological zones are needed to strengthen generalizability. Practical implications Findings underscore the need for soil remediation, crop monitoring and regulatory control to restrict high-accumulating crops in contaminated areas. Originality/value This is the first integrated, seasonally resolved assessment linking water, soil and crop contamination, revealing inconsistencies between water quality standards and actual food safety outcomes in reuse-based agriculture.