Abstract: Effects of sepiolite,lime and phosphate immoblizing cadmium and lead in contaminated paddy soil in the Diaojiang catchment,Guangxi were investigated through a field experiment,and mechanisms of the effects were analyzed through fractionation of the polluatants in the soil.Results show that the use of these amendments markedly increased yield of the crop,both grain and straw,to the greatest extent,by 25.4% and 28.3%,respectively.The effect of combined application of sepiolite and phosphate was the most significant.The application of these immobilizers significantly decreased Cd and Pb concentrations in all the parts of the plant.Especially in brown rice,the drop reached 65.12% and 61.86%,respectively.The effect of combined application of the immobilzers was more significant than that of the application of only one kind of immobilizer in the above-ground part of the plant.The brown rice produced in the treament of combined application of sepiolite and phosphate or lime met Maximum Levels of Contaminants in Foods(GB 2762-2005) in Cd concentration.The application of immobilizers,combined or single,significantly reduced the concentrations of TCLP-extractable Cd and Pb(TCLP,i.e. toxicity characteristic leaching procedure),with the maximal possible reduction reaching 28.86% and 45.60%,respectively.Combined application was obviously more effective than the application of only one.To sum up,combined application of sepiolite and phosphate is the most effective recommendation for remediation of Cd and Pb contaminated paddy soil by immobilizing the pollutants in Diaojiang catchment,Guangxi.

Key words: immobilization, sepiolite, lime, phosphate, rice, cadmium, lead, Diaojiang River