桑秆生物炭对污染土壤氧化还原过程中重金属的固持效应

Effect of Mulberry Stems Biochar on Immobilization of Cd,Pb and Zn in Redox Dynamic Soil

生物炭是一种绿色可持续的土壤稳定化药剂,在土壤重金属污染治理中应用广泛。土壤中重金属的行为受土壤理化性质的影响。在南方稻田土壤水旱交替轮作引起的氧化还原过程中,土壤理化性质发生改变,土壤的长期安全利用存在一定风险。以南方常见农林废弃物桑秆为原料,采用“水-火联动”原位制炭技术制备得到桑秆生物炭(SG-BC)并进行表征,通过溶液批平衡试验,探究SG-BC对铅(Pb)、锌(Zn)和镉(Cd)的吸附特征及机制。结果表明,SG-BC对Pb、Zn和Cd的最大实际吸附量分别为21439、4110和2575 mg·g^(-1);SG-BC对上述重金属的吸附机制主要包括络合、沉淀和阳离子-π电子配位等。开展室内土壤培养试验,探究氧化还原过程中添加SG-BC对土壤理化性质和重金属含量的影响。结果表明,施加SG-BC会引起土壤pH上升及Eh略微降低;在厌氧培养期SG-BC对土壤中重金属的释放均有不同程度的抑制作用;在曝氧培养阶段尤其是曝氧初期,SG-BC显著降低土壤溶液重金属浓度,对Pb、Zn和Cd的固持效率最高分别达9669%、8077%和7841%。研究结果表明,在氧化还原过程中,SG-BC能有效固定土壤中重金属。该研究可为生物炭应用于重金属污染农田土壤修复提供理论依据。

Biochar,as a green and sustainable soil stabilization agent,has been widely used in the remediation of heavy metals(HMs)contaminated soil.The migration and transformation of HMs are highly affected by the physicochemical characteristics of soil.Under the change of redox process caused by flooding-drainage intercropping in paddy soils,the fluctuation of physicochemical characteristics of soil will threaten the long-term safety of land utilization.Here,a mulberry stem was selected as feedstock to produce biochar by the in situ“water-fire coupled”method.The derived biochar was not-ed as SG-BC.The capability and mechanisms of SG-BC adsorbing Cd,Zn,and Pb were investigated.The results show that the maximum adsorption capacities for Pb,Zn,and Cd of SG-BC were 21439,4110,and 2575 mg·g^(-1),respectively.The mechanisms were clarified as surface complexation,precipitation,and cation-πinteractions.In addition,a soil micro-cosm incubation experiment was conducted under redox dynamic conditions to explore the impact of SG-BC on the soil Eh and pH,and the immobilization of HMs.The results show that compared to the control,the addition of SG-BC could in-crease soil pH,slightly decrease soil Eh,and inhibit the soil HMs release at various degrees during flooding,and the inhi-bition was more strong during drainage,especially in the early stage;SG-BC decreased the concentrations of Pb,Zn,and Cd in soil solution by 9669%,8077%,and 7841%,respectively.These results indicate that SG-BC is effective to im-mobilize Cd,Zn,and Pb in the soil with dynamic redox processes.This study provides theoretical basis for applying bio-char to remediate HMs contaminated agricultural soil.