Heavy metal accumulation in different organs of plants grown under high sewage sludge doses

Excessive applications of sewage sludge have led to the accumulation of potentially toxic elements in plants and soils. The objective of this study was to evaluate the effects of various sewage sludge rates (0, 10%, 20% and 40%, w/w) on yield and accumulation of heavy metals in different organs of plants grown on a calcareous soil. Bean and chickpea plants were grown in pot conditions with four replications. The investigated heavy metals were Cd, Cr, Cu, Ni, Pb and Zn. The translocations of such metals in the plant leaf, grain, stem and root were also determined. Sewage sludge treatments increased grain and biomass yield of bean and chickpea, and did not cause any disturbances of mineral nutrition. The level of heavy metals was higher in roots, followed by leaves, with increasing amounts of sludge. However, zinc was mostly accumulated in roots, but also significantly increased in the other organs of both species. Sludge treatments did not lead to large variations in Cd, Cu and Pb concentrations of grain and stem of both species. However, Cd, Cu and Pb were highly accumulated in roots. With an increase in sludge amount, leaf, grain and stem Cd concentrations of chickpea did not change, but root Cd increased significantly, about 36-fold in relation to the control. It is concluded that the largest heavy metal accumulation occurred in roots, and the phytotoxic levels of the tested heavy metals on above-ground organs (leaf, grain and stem) were not exceeded at high sewage sludge rates.