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366379 
Journal Article 
Reducing bioavailability of some heavy metals in a contaminated soil using phosphate amendments 
Zied, MMAA 
2007 
47 
1 
9-22 
Two phosphate compounds differing in water solubility, i.e., diammonium phosphate (DAP) and phosphate rock (PR), were evaluated for their ability to reduce Zn, Pb and Cd bioavailability in a contaminated soil under a wheat-maize cropping sequence installed through a greenhouse pot experiment. The corresponding application rates of P were 0, 400, 600 and 800 kg/fed for PR and DAP. Results showed that both applied phosphate agents of DAP and PR succeeded in reducing the bioavailability of Zn, Pb and Cd as well as those phytoavailability to the grown plants of wheat followed by maize. The bioavailable metals contents showed a tendency to decreased by increasing application rates, with a rather greater response for DAP at the first crop (wheat) as compared to the second one (maize), suggesting that DAP has directly greater potential to immobilize the heavy metals. Sequential extraction results indicated that the application of phosphate amendments led to convert significant amounts of the soil Zn, Pb and Cd from non-residual form (i.e., water soluble, exchangeable, carbonate, Fe-Mn oxides and organic matter fractions) to residual one. DAP was more effective in transforming soil Zn, Pb and Cd from the non-residual to the residual phase than PR at the first phase of wheat-maize cropping sequence, and then the differences became narrow in range. From technical and economic point of view, chemical immobilization of heavy metals using DAP is an effective technique method of reducing heavy metals solubility and mobility on a short term of use, but it is expensive due to the relative high cost of its production as a compound fertilizer for N and P. 
application rates; bioavailability; cadmium; diammonium phosphate; heavy metals; immobilization; iron oxides; lead; maize; manganese oxides; nitrogen-phosphorus fertilizers; phosphates; polluted soils; rock phosphate; soil amendments; soil organic matter; soil pollution; soil types; solubility; wheat; zinc; Triticum; Triticum aestivum; Zea mays; Poaceae; Cyperales; monocotyledons; angiosperms; Spermatophyta; plants; eukaryotes; Zea; corn; organic matter in soil; phosphate rock; sequential extraction; Field Crops (FF005) (New March 2000); Plant Production (FF100); Soil Chemistry and Mineralogy (JJ200); Fertilizers and other Amendments (JJ700); Pollution and Degradation (PP600); Industrial Wastes and Effluents (XX400)