Effect Of Four Soil Amendments On Behavior Of Cadmium In Polluted Soil

In this research,effects of four kinds of soil amendments which are oyster shell(OS),potash feldspar(PF),dolomite(DM)and organic matter(OM)on the cadmium(Cd)behavior in polluted soil are studied by constant temperature incubation experiment and pot experiment.And effect of moisture on the effectiveness of soil amendments to reduce the availability of Cd is also studied.The aim of this study is to provide scientific basis for the application of soil amendment in soil remediation which was contaminated by Cd lightly.The main conclusions are as follows:(1)Under constant temperature incubation experiment,3 kinds of soil amendments of mineral source which are OS,PF,DM effectively reduce the effectiveness of Cd in contaminated soil and keep for a long time.The soil amendments of mineral source could significantly increase soil pH,CEC.The treatments of soil amendments of mineral source with application 1% and 2%,soil pH increase from 4.5 to around 7.0,and soil CEC increase by 22.7%-58.8%.The soil amendments of mineral source significantly decrease availability of Cd.After 111 d incubation,the treatments of soil amendments of mineral source with adding 1% and 2%,exchangeable Cd(Exch-Cd)decrease by 93.6%-98.5%,and the effect of OS on Cd availability is the best,which make Exch-Cd decrease by 98.4% and 98.5%.There is no difference between the treatments of addition of 1% and 2%.(2)The soil amendments of mineral source also show the effect of reducing the cadmium availability in the contaminated soil,and significantly reduce the cadmium content of rape and increase biomass of small rape by pot experiment.The results show that with addition of 1% amounts of OS,PF and DM,soil pH respectively increase from 4.1 to 7.5,7.1 and 7.1,and CEC increase by 55.9%,26.3% and 15.0% separately.The amounts of exchangeable Cd(Exch-Cd)decreased by 81.1%,65.1% and 63.6% separately,while the amounts of EDTA-Cd increased by 121.6%,132.0% and 106.3%.Besides,Cd concentration in small rape respectively decrease by 83.9%,78.9% and 82.3%,while biomass increase by 990%,690% and 800%,with application of OS,PF and DM amendments.(3)Under the flooding condition,OS,PF,OS+OM and PF+OM treatments make soil pH increase to about 7.0,and CEC increase by 20.7%-30.3%.After 70 d incubation,soil pH are increased 0.26-0.94 units and soil CEC decrease by 0.8 cmol(+)/kg under flooding condition,respectively,compared with 70% field capacity.Under flooding condition,OS,PF and their combination with OM can reduce more Exch-Cd content.The contents of Exch-Cd decreased by 83.7%-97.7%,EDTA-Cd increased by 71.9%-111.9% with the addition of OS,PF,DM and its combination with OM soil amendment after 70 days flooding.The results show that OS,PF,DM could effectively improve the cadmium contaminated soil and keep a long time,and have effect of reducing Cd content and increasing biomass of small rape.Under the flooding condition,OS and PF have better effect.