PHYTOAVAILABILITY AND CHEMICAL SPECIATION OF Cd IN DIFFERENT Cd-CONTAMINATED SOILS WITH CROP STRAW INCORPORATION

Straw returning is an important way to increase soil organic matter. Pot experiment under greenhouse conditions was conducted to investigate the phytoavailability and chemical speciation of cadmium(Cd) in two different types of Cd contaminated soil with crop straw incorporation. Results indicated that uptake of Cd by maize was increased by crop straw incorporated into both natural Cd-contaminated soil and artificial Cd-contaminated soil. Crop straw incorporation also increased soil pH and dissolved organic carbon(DOC). Meanwhile the water soluble Cd concentration was increased in natural Cd-contaminated soil but decreased in artificial Cd-contaminated soil when the soil DOC increased. Majority of Cd existed in exchangeable fraction, but the concentration of Cd in exchangeable fraction reduced significantly with crop straw incorporated into both the two types of Cd-contaminated soil. Carbonate Cd concentration was increased in artificial Cd-contaminated soil. Therefore, crop straw incorporation may be a workable way to remediate soil, but the potential risk should be evaluated.