Zinc Immobilization in Two Zn-Spiked Soils

Chemical immobilization is an operative approach to reduce detrimental effects of heavy metals in soils. The present study was conducted to test the usefulness of this procedure to decrease soluble and DTPA-extractable Zn in two Zn-spiked (addition of 200 mg Zn kg–1soil from zinc sulfate and incubation for two weeks at 25±1ºC) acid and alkaline soils. In order to study the effect of submergence، two Zn-spiked acid and alkaline soils under two moisture conditions (field capacity [FC] and submergence [S]، with and without 50 g cow manure/kg soil [M]) were incubated for one month. Results showed that S+M treatment caused a markedly decrease in soluble and DTPA-extractable Zn in both alkaline (97 and 75%، respectively) and acid (85 and 78%، respectively) soils. To evaluate the effect of phosphate amendments، 5 g P/kg soil from various sources (Ca(H2PO4) 2. H20، Ca3 (PO4) 2، H3PO4، K2HPO4 and KH2PO4) was added to the Zn-spiked acid soil. Results showed that the K2HPO4 treatment caused a markedly decrease in soluble Zn (88%). Neverthless DTPA-extractable Zn decreased (12. 5%) in Ca3 (PO4) 2 treatment. In another experiment the addition of calcium carbonate to acid soil (10 g CaCO3 kg-1 soil) caused a markedly decrease in soluble and DTPA-extractable Zn (97 and 43%، respectively).