Soil samples were collected from experimental fields plots irrigated with raw I
sewage water for different periods (3, 10 and 30 years) to investigate the solid-phase I
speciation of Cu, Zn, Cd, Ni and Pb in calcareous soil. A sequential extraction
procedure was used to fractionate heavy metal into designated forms of
exchangeable (Exch.), sorbed (Sorb.), organically bound (Org.), precipitated (Prec.)
and residual (Resi). The obtained results showed that the residue fraction was the
most abundant fraction in the control soil for all studied metals , followed by the
precipitated ( carbonate) fraction, while in the waste water irrigated soil, the average
highest metal fraction, as percentage of total, was recorded as fellows: org -bound for
co. preci.-bound for Pb and resid. form for Zn, Cd and Ni. The distribution of solid ...!
phase metals in the different fractions did not significantly change as a result of
sewage water irrigation. In some cases, metals in soils irrigated with sewage water
tended to shift from less to more soluble forms. according to the period of irrigation
with sewage water.