蚯蚓/改性生物炭对As污染红壤的稳定化效应

以砷(As)污染红壤为研究对象,以耐污染能力强的赤子爱胜蚓(Eisenia foetida)为土壤动物,采用生物学模拟试验方法,探讨了铈锰改性生物炭(Cerium-manganese modified biochar,MBC)与蚯蚓联合作用对As污染红壤的稳定化效应。结果表明:将蚯蚓接种于As污染红壤中,大幅降低了土壤中水溶态As(WSAs)含量和pH值;其中蚯蚓与MBC联合作用时钝化效应最为明显,60 d时,土壤中WSAs含量降低幅度为77.59%,同时pH值比对照同期降低0.84个单位,蚯蚓与MBC对土壤As表现为协同钝化作用;蚯蚓与MBC的联合作用,促进了土壤As结合形态由活性较强的非专性吸附态和专性吸附态向无定型/弱结晶水合铁铝氧化物结合态、结晶水合铁铝氧化物结合态和残渣态等稳定态的转化。因而,MBC与赤子爱胜蚓联合作用可使土壤中As的移动性和环境风险大幅降低,且蚯蚓的生存状况良好,其与MBC的联合作用可实现As污染土壤的修复。

Immobilization effect of earthworm/modified biochar on arsenic in contaminated red soil

In order to explore the immobilization effect of cerium manganese modified biochar(MBC) and earthworms on contaminated red soil, a biological simulation experiment was carried out using the earthworm Eisenia foetida, which has a high tolerance to heavy metal pollution in soils, and the results showed that earthworms significantly decreased water soluble arsenic content and reduced the pH of the soil. When the earthworms were combined with MBC, the immobilization effect was more obvious. The content of water-soluble arsenic in soil decreased by 77.59%, and the pH decreased by 0.84 units compared with the control at the same period, indicating a synergistic inactivation of earthworms and MBC on arsenic(As) in soils. It also illustrated that the combination of earthworms and MBC in soils led to the conversion of active arsenic to a stable form, which showed the conversion of As species from non-specifically sorbed and specifically sorbed phases to non-crystallized hydrous oxides of Fe and Al, well-crystallized hydrous oxides of Fe and Al, and residual ones. This investigation indicates that the modified biochar combined with Eisenia foetida greatly decreases the mobility of As in soils, and therefore reduces the corresponding environmental risk, and the application of biochar or MBC has no significant effect on the survival of earthworms. Therefore, the use of earthworms combined with MBC is a promising method for the remediation of As contaminated red soil.