土壤二苯醚类除草剂污染残留的生物协同降解效应与机制

The extensive application of Diphenyl ether herbicides (DEHs) with good activity and selectivity caused the damage to next-stubble crop and non-point source pollution becaused of long half-lives. There is currently no efficient remediation of farmland contaminated with diphenyl ether herbicides. According to the research line of effect - process - mechanism, the project is to clarify the effect relationship between the contribution rate of the humus components of northeastern black soils to the commonly used DEHs fomesafen in soybean fields and selective feeding of humic components by earthworm and to elucidate the collaborative effect and process of earthworm and indigenous microorganism on the biodegradation of fomesafen, which is the commonly used DEHs in the soybean field. The northeastern black soil is selected as the model farmland soil ecosystem. Indoor microcosmic experiment and outdoor field control experiment will be carried out silmutaneously. The collaborative mechanism of fomesafen degradation by the two key soil biological species will be revealed from the aspects of pollutant availability, earthworm intestinal flora and soil microbial community structure and functional diversity. Combining the methods such as stable isotope probe (DNA-SIP) and Illumina / HiSeq high-throughput DNA sequencing, the segregation and identification techniques of the functional microbes in situ soil will be established and optimized. The characteristics of community structure succession, mechanism and its main control factor will be elaborated. The study will provide theoretical support for clarifying the key recovery process of soil ecosystem and its synergistic biological driving mechanism and exploring new environment-friendly remediation technology.

二苯醚类除草剂(DEHs)是目前广泛使用的强活性和选择性除草剂，其较长半衰期造成的土壤残留会对后茬作物产生药害并引起面源污染。本项目拟将黑土野外生态对照实验和室内微宇宙控制实验相结合，以效应-过程-机理为研究主线，揭示东北黑土腐殖质组分对大豆田常用DEHs氟磺胺草醚的吸附结合贡献率与蚯蚓选择性取食腐殖质组分之间的效应关系，研究蚯蚓和微生物对氟磺胺草醚生物降解的联合驱动效应和过程，从污染物有效性、蚯蚓肠道菌群和土壤微生物群落结构和功能多样性等方面揭示两类关键土壤生物类群降解氟磺胺草醚的协同机制。将稳定同位素探针技术和高通量测序技术等宏基因组学方法相结合，建立并优化土壤DEHs降解的功能微生物原位分离鉴定技术，揭示群落结构演替特征、机制及其主控因子。为明确土壤生态系统关键恢复过程及其生物协同驱动机制，探索新的环境友好型污染修复技术提供理论支撑。

农药的不合理使用导致我国当前农田土壤质量状况堪忧，如何评价土壤中除草剂对土壤生态系统的毒性影响以及清洁高效的去除其残留毒性成为当前亟待解决的问题。本项目通过运用现代分子生物学手段研究土壤动物-微生物中功能群落特征，阐释土壤生态系统质量修复关键生物过程。通过温室微宇宙实验，阐明土壤动物和土著微生物对除草剂降解的联合驱动效应和过程，揭示两类关键土壤生物类群对除草剂降解的协同驱动机制。项目紧密围绕设定的研究任务与研究方案开展相关的试验与研究工作，现已完成项目申请书与任务书中的研究任务与研究内容，主要成果如下：蚯蚓对不同除草剂降解的影响差异较大，富集作用也有明显的区别。添加蚯蚓后土壤中莠去津、2,4-D和异丙甲草胺的降解率分别提高了2.1%、2.6%、52.7%，氟磺胺草醚降解率几乎没有变化。除草剂对于蚯蚓体内能源代谢及应激系统产生了多样化的胁迫效应，显著重塑了蚯蚓肠道微环境中的微生物群落多样性和群落组成。细菌Blastococcus、Geodermatophilus、Arthrobacter、KD4-96和JG30-KF-CM45的丰度在蚯蚓不同肠段中有所升高。预暴露处理蚯蚓对于异丙甲草胺和氟磺胺草醚污染土壤的修复效应差异显著。添加预暴露蚯蚓的处理中异丙甲草胺的浓度下降速率前期快于自然蚯蚓处理，蚯蚓体内富集的除草剂进入到土壤使得预暴露蚯蚓处理中氟磺胺草醚浓度呈现上升趋势。本研究基于土壤内层种蚯蚓对土壤中常见除草剂降解趋势的不同影响，初步探讨了预暴露处理的蚯蚓与除草剂异丙甲草胺和氟磺胺草醚之间的相互作用，了解了两种除草剂对于蚯蚓的生理机能和肠道微生物群落的显著影响以及预暴露蚯蚓对两种除草剂降解效应的生物学影响机制，可为未来开展土著蚯蚓修复有机污染土壤方面的研究提供新的思路和方向，有积极的理论意义和应用前景。