干湿交替对铈锰改性生物炭固定红壤As的影响

以砷(As)污染红壤为研究对象,通过静态培养试验,探讨了铈锰改性生物炭(cerium-manganese modified biochar,MBC)在干湿交替老化条件下对红壤中As的固定效应.结果表明,与常规培养比较,干湿交替条件下MBC的施用显著降低了红壤中水溶态As(WSAs)含量(P＜0.05)和pH值,且随着材料用量的增加和培养时间的延长而持续降低,试验结束时,土壤pH值比常规条件下降低了 0.08～0.16个单位.与此同时,干湿交替条件下添加MBC后的土壤WSAs显著下降,当培养至30 d时,WSAs相比于常规培养降低了 38.73％～51.94％,比试验初期降低了 45.64％～56.19％,未添加MBC的处理在两种培养模式下土壤WSAs含量和pH值均显著升高(P＜0.05),其中以干湿交替处理更为明显.从红壤中As赋存形态看,当培养试验结束时,相比于常规培养而言,干湿交替模式下MBC的施用使土壤中非专性吸附态As(Fl)降低了 33.16％～36.00％,专性吸附态As(F2)降低了 7.67％～11.99％,残渣态As(F5)增加了 15.43％～42.45％,且土壤As的迁移系数M亦显著低于常规培养(P＜0.05),降幅为9.02％～12.75％;而未添加MBC的处理土壤As活化明显,且以干湿交替条件下更甚.整体上看,干湿交替水分管理有利于MBC对红壤中As的固定,MBC修复As污染红壤具有良好的稳定性和应用潜力.

Effect of Dry-Wet Alternation on the Immobilization of Arsenic in Red Soil by Cerium Manganese Modified Biochar

Through static incubation experiments, the immobilization effect of cerium-manganese modified biochar (MBC) on arsenic (As) in red soil under dry-wet alternation aging conditions was discussed. The results showed that compared with the routine cultivation method, the application of MBC under drying and rewetting resulted in the significant reduction of the water-soluble As (WSAs) content (P<0.05) and pH value in the red soil, which decreased continuously with the increased application amount of MBC and prolonged incubation time. At the end of the experiment, the soil pH value decreased by 0.08 to 0.16 units compared with that in routine conditions. Meanwhile, the WSAs content in soils decreased significantly after adding MBC under drying and wetting alternation. After 30 days of incubation, the WSAs contents were reduced by 38.73%-51.94% in comparison with that of the routine condition and decreased by 45.64%-56.19% compared with that in the initial stage of the experiment. However, for the treatment without MBC addition, the WSAs content in soils and pH value increased significantly under these two incubation modes (P<0.05), especially for the dry-wet alternation treatment. Compared with routine incubation, the application of MBC under alternating wet and dry modes caused the reduction of non-specifically sorbed As (F1) in the soil by 33.16%-36.00%; specifically, sorbed As (F2) decreased by 7.67%-11.99%, residual phase As (F5) increased by 15.43%-42.45%, and the migration coefficient M of soil As was also significantly decreased (P<0.05). The range for the reduced percentage was 9.02%-12.75%. However, for the treatment without MBC, As activation in the soil was obvious, which was even worse under the drying and rewetting condition. As a whole, alternate wetting and drying water management is beneficial for the immobilization of As in red soil by MBC, and MBC showed advantages and potential for remediation of As-contaminated red soil with good stability.