In high electrolyte conc. it is also necessary to take
into account the competition of Zn and the Ca present in
the soil. The more negative electro potential of the surface
soil layer explains the greater Zn adsorption at the surface
for all pH and ionic strength values, as the surface soil
layer presented more negative charges than the subsurface
for a same pH values. It is finally concluded that, there
was a pronounced increase of Zn adsorption with pH
elevation and a reduction of ionic strength of background
electrolyte. Results showed that the metal ion was more
strongly adsorbed at lower ionic strengths while any
increases in electrolyte concentration produced a decrease