| The soil in China is seriously polluted by heavy metals,so it is necessary to study the high efficiency and environmental protection stabilizer to alleviate the soil pollution.Attapulgite is a kind of clay mineral with abundant reserves.It can be hydrolyzed in soil to form colloidal particles with strong adsorption force and absorb free heavy metal ions in soil.Organic matter can reduce the water soluble and acid soluble content of heavy metals in soil by chemical action such as complexation.In this study,attapulgite and organic matter were mixed into 7 stabilizers in the proportion of 1:0,7:3,6:4,1:1,4:6,3:7 and 0:1.Seven attapulgite organic stabilizers were added to heavy metal polluted soil at 4%ratio.After stabilization for 30 days,the physical and chemical properties of stabilized soil and the bioavailability and chemical morphology of Cd,Zn,Cu,Ni,Cr and Pb were determined.The content of Cd,Zn,Cu,Ni,Cr and Pb in the corn plants and the enrichment and transport coefficient of heavy metals were calculated.The stabilization effect of Attapulgite on Cd,Zn,Cu,Ni,Cr and Pb in heavy metal polluted soil was analyzed by comparing the bioavailability and chemical forms of heavy metals in the soil stabilized by the combined stabilizer,the root length,stem length,dry weight,fresh weight,heavy metal content and the transport and enrichment coefficient of corn,The optimum proportion of attapulgite compound organic matter was determined.The experimental results show that:（1）The 7 kinds of attapulgite compound organic matter stabilizers were added to the contaminated soil at the ratio of 4%,the p H,EC and CEC of the soil increased first and then decreased with the decrease of attapulgite proportion.When the compound ratio of attapulgite and organic matter was 6:4,the p H,EC and CEC in the soil increased by 27.73%,26.18%and63.43%,respectively.When the ratio of attapulgite and organic matter is 6:4,the effect of Stabilizer on soil physical and chemical properties is better than single attapulgite stabilizer and single organic matter stabilizer.（2）The bioavailable contents of Cd,Zn,Cu,Ni,Cr and Pb in the contaminated soil decreased at first and then increased with the decrease of attapulgite proportion.When the ratio of attapulgite to organic matter was 6:4,the bioavailability of Cd,Ni,Cr and Pb in the stabilized soil was the lowest.Compared with the control,the content of Ca Cl2 in Cd,Ni,Cr and Pb decreased by 51.96%,43.86%,35.59%and 35.22%,respectively;compared with the control,the content of DTPA decreased by 50.77%,44.55%,34.30%and 30.98%respectively;compared with the control,the extraction content of TCLP decreased by 53.00%,42.67%,27.20%and 39.66%respectively.When the ratio of attapulgite to organic matter was 4:6,the contents of Ca Cl2,DTPA and TCLP extracted forms of Zn in the stabilized soil were the lowest,which decreased by 38.04%,40.31%and 35.34%respectively compared with the control.When the ratio of attapulgite to organic matter was 1:1,the contents of Ca Cl2extractable,DTPA extractable and TCLP extractable Cu in the stabilized soil were the lowest,which decreased by 52.86%,53.54%and 50.72%respectively compared with the control.（3）Attapulgite combined with organic stabilizer can promote the transfer of heavy metals from acid soluble and reducing to oxidation and residue.The residue content of heavy metals in 7 stabilized soils increased with the ratio of the contrast.When the ratio of attapulgite and organic matter in passivating agent was 6:4,the residue content of Cd,Ni,Cr and Pb in the stabilized soil was the highest,and the content of Cd,Ni,Cr and Pb in the stabilized soil increased by 18.94%,21.21%,16.74%and 22.46%respectively compared with the control;When the ratio of attapulgite and organic matter in stabilizer is 1:1,the residual content of Cu in stabilized soil is the highest,which increases by 12.36%compared with the control;When the ratio of attapulgite and organic matter in stabilizer is 4:6,the residual component of Zn in stabilized soil is the highest,and the ratio of Zn in stabilized soil is 14.86%higher than that of the control.（4）Attapulgite combined with organic matter stabilizer can significantly improve the root length,stem length,dry weight and fresh weight of maize.The effect of biomass of Maize on the proportion of attapulgite in stabilizer showed a trend of first increasing and then decreasing.The root length,stem length,dry weight and fresh weight of maize grown in the stabilized soil were the largest when the ratio of attapulgite and organic matter was 6:4.（5）Attapulgite combined with organic matter stabilizer can significantly reduce the content of heavy metals in maize and inhibit the accumulation and transport of heavy metals in maize.The content of Cd,Ni,Cr and Pb in the stabilized soil was the lowest,and the enrichment coefficient and transport coefficient were the lowest;When attapulgite was mixed with organic matter in the ratio of 1:1,the content of Cu in corn was the lowest,and the enrichment and transport coefficient of Cu was the lowest;The stabilizer composed of attapulgite and organic matter in the ratio of 4:6 had the lowest Zn content in corn,and the lowest Zn transport and enrichment coefficient.（6）The stabilization efficiency of attapulgite compound organic matter to heavy metals is higher than that of single stabilizer,and the environmental risk index of compound stabilizer to heavy metals in soil is lower than that of single stabilizer.When the ratio of attapulgite and organic matter was 6:4,the stabilization efficiency of Cd,Ni,Cr and Pb in passivated soil was the highest,and the environmental risk index was the lowest.（7）The stabilization effect of attapulgite combined with organic matter Stabilizer on heavy metals in soil is better than that of single stabilizer.When the ratio of attapulgite and organic matter is 6:4,the stabilization effect of Cd,Ni,Cr and Pb in contaminated soil is the best;When attapulgite is mixed with organic matter in the ratio of 1:1,the stabilizer has the best stabilization effect on Cu in soil;When the ratio of attapulgite and organic matter is 4:6,the stabilization effect of Zn in soil is the best.Attapulgite combined with organic matter stabilizer has the advantages of simple preparation method,low cost,environment-friendly,and can be applied in large area.It has a broad prospect in the stabilization and remediation of heavy metal contaminated soil. |
