Chemistry of Zinc Added to Soils and Clays
Nelson, J. L. | Melsted, S. W.
The chemical forms which zinc assumes when added to soils and clays have been investigated, using the isotope dilution technique (with Zn⁶⁵ as a tracer). After equilibrium, the added zinc was extracted by successive leaching with neutral normal NH₄Ac, 2.5% HAc, and 0.1 N HCl. Variables were: (1) time of equilibrium, (2) calcium saturation, (3) amount of zinc added, (4) rate of extraction, and (5) type of clay mineral. With symmetry additions of zinc and a hydrogen soil system, practically all of the zinc taken up by the soil was replaceable with NH₄Ac, whereas in a calcium soil system a part of the zinc could not be replaced with NH₄Ac. The portion of the zinc not removed with NH₄Ac could be extracted by repeated leaching with dilute HCl. This acid-soluble form of zinc increased with increasing length of time of contact between the soil and the zinc solution. It apparently did not occupy exchange sites in the soils, since there was no reduction in the base-exchange capacity of the soil with the formation of the acid-soluble form. As smaller quantities of zinc were added to these soils and as the amount of time following the addition increased, a higher proportion of the zinc was found in the acid-soluble form.Show more [+] Less [-]