Assessment of Lead, Copper and Cadmium Tolerance by Four Vegetable Species

Heavy metal pollution in agriculture soils has serious negative effects on human health and has become an important issue both in developed and developing countries. This study was conducted in ElOurdanine region (Monastir, Tunisia) and performed at four different sites using treated wastewater for irrigation. The aim is to detect the ability of accumulation of some heavy metals by four vegetable crops: peas (leguminosae), carrot (Apiaceae), lettuce (Asteraceae) and spinach (Chenopodiaceae) grown in contaminated soil. Total of 4 soils samples from the four experimental sites were collected and analyzed before and after vegetables cultivation. The quantitative content of Cadmium (Cd), copper (Cu) and lead (Pb) in the four species revealed differential abilities of accumulation. Significant differences were recorded. The comparison of the four species together showed that lettuce and spinach are the most accumulators of heavy metals, an average concentrations above than 7.50 mg.kg -1 DM were recorded, while the pea pods were characterized by the lower concentrations (<0.5 mg.kg -1 DM for Cd), carrot expressed a moderate accumulation with an average of four sites not exceeding 3 mg.kg -1 DM for Cd. The lower accumulators (pea and carrot) would be most suitable for cultivation on contaminated soils while both spinach and lettuce appear to be high accumulators of Cd and Pb that are considered a higher risk to human health than Cu.