生物炭重构蚓触圈微环境下污泥-蚯蚓多界面重金属迁移转化机理研究

This study adopted three kinds of biochar and two epigeic earthworm to vermicompost the urban sewage sludge. Based on the survival characteristic of earthworm in the biochar amended sludge, under different mode and condition (different kinds of biochar, earthworm and stage) of vermicompost, the topics were discussed: (1) The distribution of heavy metals forms in intestinal tract, mucus, feces and sludge were investigated and the relationship between heavy metals forms and environmental factors (microstructure, composition properties, phsico-chemical properties, microbial properties, etc ) in micro-interface was also evaluated. Therefore, the rules of variation for the heavy metals activity in multi-interface could be revealed. Also, the mechanism of variation of heavy metals activity in multi-interface modified by the variation of microenvironment could be revealed; (2) Base on the in situ analysis and concentrations analysis of heavy metals in intestinal tract and epidermis in earthworm, together with the concentration of heavy metals in sludge, the approach of heavy metals transfer from sludge to earthworm could be found out. Through the analysis of relationship between environmental factors, heavy metals forms in micro-interface and the metals in intestinal tract and epidermis, the mechanism of heavy metals transferred to intestinal tract and epidermis could also be disclosed; (3) Based on the microdistribution analysis of heavy metals in intestinal tract and epidermis, by construction of the relationship between microdistribution and enrichment of heavy metals in earthworm and heavy metals in sludge, the mechanism for the variation of the bioaccumulation ability of heavy metals in earthworm could be found out. Based on the mentioned above, the mechanism of heavy metals migration and transformation between the sludge and earthworm in drilosphere environment reconstructed by biochar would be concluded. This study could supply the sludge recycling with new research direction.

本研究拟用三种生物炭与两种表居型蚯蚓堆肥城市污泥，基于生物炭重构蚓触圈微环境中蚯蚓存活特性分析，在不同堆肥模式和堆肥条件下(不同类型生物炭、蚯蚓种、堆肥阶段)，主要研究:(1)肠道、粘液、蚓粪、污泥中重金属形态变化及与微界面环境因子(微观形貌、组成特性、理化因子、微生物特性等)的关系，以阐明多界面重金属活性变化规律，探明微环境变化下多界面重金属活性转变机理(2)依据肠道/表皮中重金属原位分析、浓度分析，结合污泥中重金属浓度分析，查明重金属迁移至蚯蚓途径，通过建立微界面环境因子、重金属形态与肠道/表皮中重金属联系，揭示污泥中重金属迁移至肠道/表皮机理过程(3)根据肠道/表皮中重金属微分布分析，构建蚯蚓中重金属微分布、富集量与污泥中重金属浓度内在关联，查明蚯蚓富集重金属能力变化机制。通过上述研究，归纳生物炭重构蚓触圈微环境下污泥-蚯蚓多界面重金属迁移转化机理。本研究将提供污泥资源化新研究方向。

污泥中高浓度重金属会产生一定生态风险。采用蚯蚓好氧堆肥方式，通过对微环境和大环境污泥多界面重金属测试分析，探讨不同生物炭类型、添加比例和堆肥阶段等对蚓触圈和污泥大环境中重金属影响，结合蚯蚓体内不同尺度重金属分析，探索了肠道、粘液、蚓粪、污泥等多界面中重金属活性变化规律，查明了污泥中重金属迁移至肠道/表皮机理过程，揭示了蚯蚓富集污泥中重金属机制。由此，归纳了生物炭重构蚓触圈微环境下污泥-蚯蚓多界面重金属迁移转化机理。. 研究主要发现：蚯蚓在污泥中适应性随生物炭类型和添加比例变化，低浓度生物炭促进适应性，高浓度生物炭抑制适应性，秸秆炭和竹炭仅改变污泥pH提升适应性，稻壳炭综合改善污泥pH、EC和有机质提升蚯蚓适应性；蚯蚓适应性变化体现在蚯蚓整体、表皮、肠道酶活性（SOD、POD、CAT等）变化过程，且此种酶活性变化更主要与肠道污泥和穴壁污泥微环境因子变化有关；生物炭促进了肠道污泥中重金属被肠道吸收，穴壁污泥中重金属被表皮吸收；生物炭显著改变蚯蚓亚细胞组分（细胞溶质、细胞碎片、固体颗粒中）中重金属：稻壳炭对蚯蚓细胞溶质、细胞碎片、固体颗粒中重金属增加作用大于秸秆炭和竹炭。不同生物炭改变不同微环境因子导致了重金属在肠道、表皮及亚细胞组分中分布差异性；生物炭改变污泥和蚓粪理化性质将蚓粪中重金属交换态和有机结合态向残渣态转化；生物炭协同蚯蚓粘液作用污泥中重金属，使得污泥中重金属浓度进一步降低，促进重金属交换态和碳酸盐结合态逐渐向残渣态转化。由此，不同生物炭协同蚯蚓堆肥均能使得污泥中重金属有效性降低，但不同生物炭在不同微界面转化污泥中重金属能力并不同。. 综上，蚯蚓和生物炭联合堆肥调控了污泥中重金属浓度，也改变污泥中重金属活性，通过在不同界面改变微环境因子，促进宏观污泥中环境因子变化，将重金属从易迁移形态转化为稳定形态，达到稳定化污泥中重金属作用，本研究可为污泥资源化利用提供新技术和新方法。