Abstract: Soil samples were collected from a heavily contaminated zone in an electroplating plant site for stabilization test using biochar derived from straw.Variation of the heavy metals in amount and form with the rate of biochar amended into the soil was analyzed.Results show that biochar changed the forms and distribution of heavy metals in the soil and had some significant effect stabilizing the polluted soil,particularly on Cr.With increasing biochar amendment rate,the content of residual form of Cr increased significantly.Especially in the treatment of 100 g·kg^-1 biochar,the content of residual Cr increased by 59.51 mg·kg^-1,as compared with that in CK(1 098.75 mg·kg^-1),being the largest increment.The effect of stabilizing Cu and Ni was closely related to biochar amendment rate: when biochar was added up to or over 70 and 30 g·kg^-1,its remediation effect on Cu and Ni was quite obvious,but not on Zn in the soil.When biochar amendment rate was 50 g·kg^-1,the total content of the 4 heavy metals(Cu,Cr,Ni and Zn) in residual form increased up to 1 805.95 mg·kg^-1,much higher than 1 745 mg·kg^-1 in CK.The biochar amendment rate was quite reasonable. 

Key words: contaminated sites, heavy meta, chemical forms, biochar, fixation/stabilization