[Fractions Transformation of Heavy Metals in Compound Contaminated Soil Treated with Biochar, Montmorillonite and Mixed Addition]

A compound contaminated soil sampled from Lingxiang City,Hunan Province,was used to investigate the effects of biochar (BC) and montmorillonite (MM) addition on heavy metals fractions.The addition amounts of BC and MM were 1%,2%,5%,respectively,and the mixture treatment was 1% BC+1% MM.BCR (European Community Bureau of Reference) sequential extraction method was used to assess the fractions of heavy metals in soil after incubation.The results indicated that adding BC alone significantly reduced the available contents of Pb,Cu and Cd.Among montmorillonite treatments,MM5% treatment decreased the weak acid extractable content of Cu,Pb,Zn,Cd by 27.6%,19.2%,25.6%,19.2%,respectively.BC+MM treatment worked well,decreased the weak acid extractable content of Cu,Pb,Zn,Cd by 15.8%,15.9%,13.1%,12.0%,and increased the residual content by 39.0%,110.1%,9.6%,62.5%,significantly reducing the mobility of the four elements.For the stabilization effect,MM treatment worked better than BC treatment,and a combination of two amendments worked the best.