黑炭负载零价铁对复合污染土壤中铜和铬的稳定化效果及生物有效性影响

Effect of zero-valent iron loaded black carbon on the stabilization effects and bioavilability of copper and chromium in combined contaminated soil

采用直接热解法和碳热还原法分别制备了黑炭(BC)和黑炭负载零价铁(BF)材料,通过土壤稳定化培养实验和盆栽实验,考察了BC和BF对复合污染土壤中铜和铬的稳定化效果及其对生物有效性的影响。实验结果表明,BC可提高土壤pH,BF则降低土壤的pH。在投加量为5 g·kg-1的情况下,处理30 d后,BC和BF对土壤中TCLP-Cu的去除率分别为76.99%和69.83%;BC对TCLP-Crtotal和TCLP-Cr(VI)去除率分别为91.07%和92.47%,BF对TCLP-Crtotal和TCLP-Cr(VI)的去除率均接近100%,两者均能有效降低土壤重金属迁移性。形态分析表明,投加BC和BF均促进了铜由酸可提取态向可还原态和可氧化态转化,同时使铬的酸可提取态降低,可氧化态增加。盆栽实验表明,BC和BF均大大降低了土壤中铜和铬的生物有效性,减弱了其由植物根部向地上迁移的能力。相比而言,BF在对复合污染土壤中铜和铬的稳定化效果、形态转化以及迁移性方面整体优于BC。

Black carbon(BC)and zero-valent iron loaded black carbon(BF)materials were prepared by direct pyrolysis method and carbothermal reduction method,respectively.Then the stabilization culture experiments and pot experiments were conducted to evaluate the effect of BC and BF on the stabilization and bioavailability of Cu and Cr in multi-contaminated soil.The results showed that soil pH increased with BC addition,while decreased with BF.The stabilization tests indicated that the removal efficiencies of TCLP-Cu were 76.99%and69.83%after 30 days treatment by BC and BF at dosage of 5 g·kg-1,respectively.The removal efficiencies of TCLP-Crtotaland TCLP-Cr(VI)with BC addition were 91.07%and 92.47%,respectively,while those with BF addition were close to 100%,this indicated that BC or BF addition could effectively reduce the migration of heavy metal in soils.The species analysis showed that BC and BF addition promoted the transformation from the acid-extractable Cu species to reducible and oxidizable ones,the transformation from acid-extractable Cr species to oxidizable ones.Pot experiments indicated that BC and BF addition could significantly reduce the bioavailability of Cu and Cr in the soil and effectively weakened the migration ability from plant roots to the ground.Consequently,BF addition is superior to BC addition in terms of the stabilization effect,form transformation and migration of Cu and Cr in combined contaminated soil.