Résumé:
"Wadi Kebir-Rhumel, surrounded by a more or less degraded riparian forest and
interspersed with wide pieces of completely denuded land, is bordered throughout by a main
road probably to be contaminated by heavy metals, particularly lead (Pb), zinc (Zn) and
cadmium (Cd). The present study has for objectives to determine the role of tamarisk grove in
the soil contamination by heavy metals.
For this purpose, ten sites were selected along the Wadi Kebir-Rhumel so as to have
a side by side plot with vegetation and bare plot. In each plot, soil samples were collected in
a central band and, on either side of it, on the side of the road and the edge of the wadi.
Tamarisk leaves have been a sampling means. The concentrations of Pb, Cd and Zn were
determined by ICP-OES in the washed, unwashed leaves and soils. These, have also been the
determination of the organic matter, pH, electrical conductivity, the total limestone (CaCO3),
cation exchange capacity and the particle size.
The results show significant differences between the washed and unwashed leaves of
tamarisk from the viewpoint of the contents of Pb, Zn and Cd, suggesting an atmospheric
origin of their contamination by heavy metals. The determination of the correlation
coefficients shows, for soils with vegetated plots, that the retention of Pb was by the organic
matter and clay, that of Zn by clay and Cd by pH and manganese. In bare plots, retention Pb
and Cd is governed by pH, CEC and silt, whereas Zn is by iron and manganese. The analysis
of variance revealed the contents of Pb, Zn, Cd, organic matter and clay for the plots under
vegetation, particularly in the middle of the tamarisk, significantly greater than in the bare
plots.
It comes out from this study that the efficiency of tamarisk grove in the retention of
metallic trace elements is the results of an important accumulation of Pb and Zn following the
retention of great quantities of clay and organic matter."
