Assessment of Pollution and Relationship between Heavy Metals Concentration in Soil and Leafy Vegetables in Zanjan Province

In recent years, the use of municipal sewage in certain areas in Zanjan city, Iran, and farms adjacent to Zn and Pb processing plants has led to accumulation of heavy metals in the soil and vegetables. In this research, the concentrations of heavy metals (Cu, Zn, Cd and Pb) in some vegetables (coriander, basil, dill, mint, savory, leek, chard, fenugreek and parsley) cultivated in six regions of Zanjan city were assessed. Results indicated that the highest concentration of heavy metals was in wastewater-irrigated soils, located around the railway. Among the studied heavy metals, Cu concentration of vegetables was higher in wastewater-irrigated farms. Concentrations of Cd, Zn, and Pb exceeded the safe limits for human consumption in all of the vegetables. The highest contaminations of Cd and Zn were found in savory samples (1.8 and 157.3 mg/kg fresh weight, respectively) and for Pb and Cu in mint (7.5 and 18.3 mg/kg fresh weight, respectively) which were higher than the Institute of Standards and Industrial Research of Iran (ISIRI) permissible values for human consumption. Provisional tolerable daily intake (PTDI) for Cd and Pb was less than ISIRI values. Therefore, long-term use of high intake of vegetables (higher than 0.058 kg/day) may have dangerous consequences on human health in Zanjan Province. However, the soil Cu concentrations showed positive significant correlation with Cu in mint (p