Accumulation and risk assessment of heavy metals in different varieties of leafy vegetables

A pot experiment was conducted to investigate the differences in heavy metal accumulation in different varieties of leafy vegetables (five leafy vegetables four or five varieties of each) and their potential risk. The results revealed that the concentrations of Cd in all the vegetables exceeded the limit for China (0.2 mg/kg) and that the As and Pb concentrations were within the limit. The bioaccumulation of Pb, Cd, and As in spinach (0.01, 1.08, and 0.02) and rape seedlings (0.004, 0.43, and 0.03) were the highest and lowest, respectively. Health risk assessments indicate that the hazard index (HI) ranged from 0.66 to 3.37 and 2.86 to 14.64 for adults and children, respectively, and the total carcinogenic risk (TCR) ranged from 2.13E-03 to 1.86E-02 and 9.27E-03 to 8.07E-02. Probabilistic health risk assessment revealed that the HI was 3.06 and 4.75, and the TCR was 2.5E-03 and 8.88E-04 for adults and children, respectively. More importantly, heavy metal accumulation significantly differed among varieties of leafy vegetables, especially spinach. The BF of Pb, Cd, and As in spinach ranged from 0.003 to 0.01, 0.77 to 1.39, and 0.01 to 0.02, respectively. Geodetector analysis revealed that oxalic acid, available As, and organic matter are the key factors that affect Pb, Cd, and As accumulation, respectively, in these vegetables. These results suggest that the planting of suitable types and varieties of vegetables can reduce the potential health risk to a certain extent and that more effective measures should be implemented to ensure the safety of local residents in areas contaminated with heavy metals.