Forms of trace metals from inorganic sources in soils and amounts found in spring barley

Abstract

Barley (Hordeum vulgare L.) was grown on a sandy soil given different doses of cadmium carbonate (salt), copper carbonate (malachite), lead carbonate (cerussite), and zinc carbonate (smithsonite) in a pot experiment conducted in a greenhouse. The element compounds were added to the soil in amounts equivalent to the following levels of the metals: Cd 5, 10, 50 μq ⁻¹; Cu and Pb 50, 100, 500 μg g⁻¹; Zn 150, 300, 1500 μg g⁻¹. Sequential extraction was used for partition these metals into five operationally-defined fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The residue was the most abundant fraction in the untreated soil for all the metals studied (43 to 61% of the total contents). The concentration of exchangeable Cd (0.2 μg g⁻¹), Cu (0.01 μg g⁻¹), Pb (0.1 μg g⁻¹), and Zn (1.4 μg g⁻¹) were relatively low in the untreated soil but increased markedly in the treated soils for Cd (up to 31 μg g⁻¹) and Zn (up to 83 μg g⁻¹), whereas only small changes were observed for Cu and Pb. The pot experiment showed a significant increase in the Cd and Zn contents of barley grown on the treated soils, but only small changes in Cu and Pb concentrations.