The accumulation of potentially toxic elements in spinach biomass grown on nine soils treated with sewage sludge

The effect of sewage application on nine arable soils with different properties was investigated in pot experiment with spinach. Uptake of eight elements (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) by plants and their availability released by 0.01 mol.l(-1) CaCl2 after the harvest were investigated. The application of sludge significantly increased biomass yield of spinach in the majority of soils used. The observed elements showed different accumulation potential and extractability. There are three elements As, Pb and Cr showing the lowest changes in the availability and accumulation by spinach at sludge treatments. Cu and Ni were easily extractable from treated soils and in case of Cu were more accumulated in plants. Highest accumulation potential was found for Cd, Zn and Hg. Cd content in plants was not changed substantially but the portion of total Cd uptake from sludge was the highest among all elements. Hg and Zn showed high accumulation in spinach at treated soils. High content of Zn in plants was confirmed by higher availability of soil Zn at treatments with sludge. Availability of soil Hg was extremely low below detection limit in all treatments.