TOTAL CONTENT AND EXTRACTABLE FRACTION OF CADMIUM, COBALT, COPPER, NICKEL, LEAD, AND ZINC IN CALCAREOUS ORCHARD SOILS

The levels and availability of six heavy metals cadmium (Cd), cobalt ( Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in calcareous orchard soils were measured in an investigation of a method for the de termination of total content and extractable fraction of these metals by atomic absorption spectrometry. The digestion step was performed co mparatively using two different types of heating. Cadmium, Cu, Ni, Pb, and Zn were determined by flame atomic absorption spectrometry (F-AAS ) and Cd was determined by electrothermal or graphite furnace atomic a bsorption spectrometry (GF-AAS) using the method of standard addition. The detection limits, precision values, and accuracy (recovery assays ) show the reliability of the method. The conditions for the determina tion of the extractable fraction of the metals were also optimized. Ex traction time for Cd and Zn was studied, and the application of two ho urs of shaking was selected. The tested method was applied to real sam ples corresponding to highly calcareous orchard soils characteristic o f the Mediterranean area. Only Zn, Cu and Pb showed high levels in the ir extractable forms, whereas Cd and Co had highest levels in their to tal contents. An important bio-availability was observed in all the st udied metals, but mainly for Cd and Pb.