Metabolic dynamics and health risk assessment of heavy metal accumulation in urban-rural interface vegetable systems

The urban-rural interface represents a critical ecological zone where anthropogenic activities intersect with agricultural systems, creating complex challenges for trace element dynamics and human health. This study comprehensively investigated the metabolic pathways, bioaccumulation mechanisms, and potential health risks associated with heavy metal accumulation in vegetables from water-scarce regions utilizing wastewater irrigation. Eight heavy metals (cobalt, nickel, manganese, iron, chromium, lead, cadmium, and zinc) were examined through atomic absorption spectrophotometers in three vegetable species (spinach, tomatoes, and cabbage) from three distinct urban-rural interfaces. Statistical analysis revealed significant variations in metal concentrations across wastewater, soil, and vegetable samples (p ≤ 0.001). Cadmium and lead concentrations in vegetables exceeded the recommended safety thresholds, with spinach exhibiting the highest accumulation levels. Bioaccumulation patterns demonstrated species-specific metal uptake mechanisms. Chromium showed maximum transfer factors in tomatoes and spinach in the East Shorkot sector, while manganese bioaccumulation was most pronounced in cabbage. Toxicological risk assessment unveiled critical insights, with spinach demonstrating the highest health risk index for lead and cadmium in adults and children populations. Tomato and cabbage exhibited maximum risk indices for chromium. The concentration gradient of heavy metals varied significantly across different vegetable species and sampling sectors. Metal transfer factors ranged from 0.2 to 1.5, indicating substantial variability in metal uptake and translocation mechanisms. The study identified potential ecological and health risks associated with wastewater irrigation, particularly cadmium and lead accumulation. This research contributes significantly to understanding heavy metal dynamics, offering crucial implications for sustainable agriculture and food security in rapidly transforming urban-rural landscapes.