Heavy metals in vegetables grown in contaminated soils

This study was focused on assessment of heavy metal contents in vegetables grown in soils contaminated by various sources in northwest Albania. Thirteen vegetable samples taken from irrigated and non-irrigated fields in Bregu i Matit Plain were analyzed for the levels of Cd, Cu, Zn, Pb and Ni using atomic absorption spectroscopy (AAS), after extraction by HNO3 and H2O2. The heavy metal contents were in the following ranges (mg kg-1): Cu 2.98-12.90 (±3.08), Ni 4.82-35.79 (±7.68), Zn <1-81.67 (±24.41), Cd 0.05-0.60 (±0.16), and Pb 0.03-0.44 (±0.11). The maximum contents of Cu, Cd, Zn and Pb were found in salad samples taken from the intensively irrigated fields and Ni in a salad sample from a moderately irrigated field, suggesting that the irrigation led to accumulation of heavy metals in plants. On the other hand, correlation analysis indicated that the metal pairs of Cu/Cd and Zn/Ni have the common origin in the studied vegetables. The transfer factor (TF) was of the order Cd > Zn > Cu > Ni > Ni. The TF values indicate that only Cd was accumulated in plants. The contents of Cd in three vegetable samples, Pb in four samples, and Cu in one sample were above the safe limits set by the FAO/WHO for heavy metals in foods and vegetables suggesting that consumption of vegetables grown in the studied soils could be dangerous to human health, and within the normal range of metals in plants except for Cu in all the samples and Ni in three samples.