农药在土壤团聚体及侵蚀条件下的赋存特征与输移过程模拟

With climate change and the increasing demand of crop production, tremendous pesticides are input into agricultural system which potentially threaten food safety and environmental health. Research on pesticide and its risks in water bodies and aquatic toxicity are frequently reported while particle-facilitated transport of pesticide and its risk to off-site related to soil erosion are still insufficient studied. To address these issues, typical soil from the Loess Plateau and common herbicide glyphosate were chosen in this project. This project thus will focus on glyphosate dissipation and decay kinetics in particle-scale of soil aggregates and its transport mechanism with soil erosion. The methodological approach used here relies on batch incubation and lab simulation experiments. The decay kinetics variation of glyphosate in soil aggregates will be measured and the content of pesticide in runoff and sorted sediment will be detected. These data were used to interpret glyphosate behaviour in soil aggregates and its likely transport mechanisms associated with soil erosion...Specific objectives of this project are: (i) to study the glyphosate dissipation and decay kinetics in particle-scale of soil aggregates; (ii) to identify glyphosate content and transport characteristics in runoff and sorted sediment related to soil erosion; (iii) and to develop a model to assess the risk of pesticide transport based on pesticide degradation and soil erosion processes. This research will improve our knowledge of pesticide dissipation in particle-scale of soil aggregates and provide insight into developing pesticide transport model associated with particle-facilitated mode and soil erosion processes in order to better understand pesticide behaviour in soil and its risks in off-site ecosystems.

随着气候变化及粮食生产的需要，农药施用的持续增加严重威胁着食品安全及环境健康。目前，对农药污染的研究大多集中在水体及水生生态毒理等方面，而对附着于侵蚀泥沙及悬浮颗粒中的农药赋存、迁移规律及对异地污染风险评估仍存在较多问题。因此，本项目以黄土高原黑垆土及常用除草剂草甘膦农药为研究对象，通过定量观测及室内模拟，研究多级土壤团聚体中农药污染物的衰减降解特征；基于降雨侵蚀力对土壤团聚体的机械破碎机制，明确侵蚀过程各级泥沙颗粒及径流中农药污染物的赋存变化及输移规律；集成农药污染物衰减降解规律及坡面侵蚀原理，构建农药污染物输移模型。期望在理论上揭示农药污染物在土壤中的环境行为及归趋，阐明农药在土壤团粒中的衰减特征及侵蚀泥沙颗粒中的赋存变化，在实践上完善农药污染环境风险评估方法，重点监测农药污染物在颗粒物中的负载及传输特征，为区域农药监控、水资源保护及生态安全风险评估提供科学依据。

随着气候变化及粮食生产的需要，农药施用的持续增加严重威胁着食品安全及环境健康。本项目本项目已农田常用农药为研究对象，通过定量观测及室内模拟，研究多级土壤团聚体中农药污染物的衰减降解特征以及土壤复合污染物的环境行为；基于降雨侵蚀力对土壤团聚体的机械破碎机制，明确侵蚀过程各级泥沙颗粒及径流中农药污染物的赋存变化及输移规律，从而集成农药污染物衰减降解规律及坡面侵蚀原理，构建农药污染物输移模型。重要结果：①不同土壤不同粒级上草甘膦农药的衰减特征差异较大，且呈现不同的变化趋势，各粒级土壤团粒中草甘膦农药的衰减特征在开始阶段差异显著，特别是粒径小于<50µm的土壤及粒径10mm-2mm的土壤团粒中，农药衰减的特征差异较大；②农田复合污染物影响下，农药在土壤中的环境行为更加复杂，特别是在降解转化及迁移等方面：如土壤中蚯蚓的活性可能受农田中复合污染物的综合影响，将土壤表层中的污染物向土壤深层进行迁移，从而对深层土壤造成威胁；如使用农药熏蒸土壤3年后需增加对P肥的施用，而农药连续熏蒸7年后，熏蒸剂农药的施用直接影响作物的产量以及土壤P的生物有效性；如农药大量喷施，不仅可能会增加土壤中农药残留的累积，而且会增加周边农户对农药的暴露风险；③剖面侵蚀条件下，泥沙分选所造成的污染物输移特征显著，特别时在微小颗粒上的复合特征及输移比率较大。因此，在后续对农药污染物进行风险评估（同位/异位）评估时，因考虑农药性质特征，特别是对其与农田其他污染物的复合迁移规律应加以深入探讨，从而有利于侵蚀条件下污染物风险的综合评价，对下游生态系统的生态安全及污染防控具有重要的研究意义。