AAS Defining of the Mobile Forms of Pb, Cu, Zn and Cd in Soils from Industrially Polluted Regions

1 Agricultural University, BG-4000 Plovdiv, Bulgaria
2 Institute of Tobacco and Tobacco Products, BG-4000 Plovdiv, Bulgaria


ANGELOVA, V., P. ZAPRJANOVA and K. IVANOV, 2002. AAS defining of the mobile forms of Pb, Cu, Zn and Cd in soils from industrially polluted regions. Bulg. J. Agric. Sci., 9: 5–12

The objective of this research is to define the mobile forms of Pb, Cu, Zn and Cd in 12 polluted in varying degrees soils from the region of Non-Ferrous-Metal Works near Plovdiv, Bulgaria. For extraction of the accessible for plants heavy metals we used the following extractants:
1) 1M KNO3; 2) 1M Ca(NO3)2; 3) 0.1 M NaNO3; 4) 1M NH4NO3; 5) 1M MgCl2; 6) 1 M NH4Cl; 7) 1 M NH4OAc, pH 7.0; 8) 1 M NH4OAc, pH 4.8; 9) 0.05 M Na2EDTA, pH 6.0; 10) 0.005 M DTPA+0.1 M TEA, pH 7.3; 11) 1.0 M NH4 HCO3 + 0.005 M DTPA, pH 7.6.
Soil samples are shaken for 1 hour at 20°C with extractants 1–9, and in the case of extractants 10 and 11 for 2 hours and 15 minutes, respectively. For extractants 1–9 the ratio soil liqiud was 1:10, and in the case of extractants 10 and 11 – was 1:2. Quantity measurements for contents of Pb, Cu, Zn and Cd were performed with a AAS 3030B flame variant of the firm "Perkin Elmer".
The extractants can be divided into two groups which differ considerably in their action and activity. Each one of the extractants from the first group (1M KNO3, 1M Ca(NO3)2, 0.1 M NaNO3, 1M NH4NO3, 1M MgCl2, 1 M NH4Cl, 1 M NH4OAc, pH 7.0) can be used successfully for defining the mobile forms of Pb, Cu, Zn and Cd in unpolluted or in slightly polluted calcaric fluvisoils. The extractants from the second group (DTPA, NH4HCO3 – DTPA and EDTA) extract also the heavy metals, organically bound, as well as bound and occluded in oxide and secondary clay minerals. The extractants from this group are more suitable for defining the available forms of heavy metals in polluted soils. NH4OAc with pH (4.8) is not pertinent for evaluation of the available forms of heavy metals, as it extracts almost the whole of their quantity.

Key words: mobile forms, Pb, Cu, Zn, Cd, defining, industrially polluted soils