土壤结合态农药的生物可利用性与潜在毒性

Pesticides are a large group of important environmental pollutants that are characterized by large usage, high toxicity and thus extensive impact on the environment. Pesticides exist in soils in both aqueous-phase dissolved and soil-bound residues. Existing theory asserts that only aqueous-phase pesticides are bioavailable and therefore possess toxic effects. We hypothesize that soil-bound pesticide residues are also bioavailable to some extent and hence potentially toxic to living organisms. This hypothesis will be tested in this project across the pesticide-soil-water-biota interfaces by determining the bioavailability of bound pesticide residues, pesticide transformation pathways, and pesticide potential toxicity. To this objective, four pesticides differing in physicochemical properties and four soils of different compositions are selected to be used. The results will be analyzed to accurately evaluate the environmental behaviors and ecological risks of pesticides in soils. The conclusions from this study will provide a supportive foundation for the environmental protection and ecological safety of China. The proposed research work includes microbial degradation, plant uptake and animal (earthworm) accumulation of soil-bound pesticide residues; product identification, pathways and mechanisms of biotransformation of pesticides; as well as potential toxicity of mixed pesticides and their transformation products. The research group, led by a recipient of the national natural science foundation outstanding young scholar’s project, comprises of three professors and other members. The research interests of group members are focused on pesticides and organic pollutants with many years of research experience. The laboratories are well equipped with various analytical instruments available for the proposed study. All these resources guarantee the successful implementation of the project leading to high-rank research production.

农药是一类用量大、毒性高的重要污染物，在土壤中以结合态和游离态两种基本形态存在。传统观念认为，只有游离态农药才具有生物可利用性，进而体现毒性效应。本研究提出结合态农药同样具有某种程度的生物可利用性和潜在毒性的观点，将选用不同理化性质的四种农药和不同成分的四个土壤，在农药-土壤-水-生物体界面上/体系中，对土壤结合态农药的生物可利用性、代谢途径和机制、潜在毒性进行深入的研究，旨在全面准确地评价农药在土壤中的环境行为和生态风险，为我国的环境保护和生态安全提供基础支撑。研究内容包括结合态农药的微生物降解、植物吸收、动物（蚯蚓）积累等方面的生物可利用性；农药生物转化产物鉴定、途径和机制；结合态农药和代谢物混合物的潜在毒性等。课题组由国家杰出青年基金获得者领衔，由包括三位教授等成员组成，研究领域涵盖农药污染的全过程，研究经验丰富，实验室装备齐全，能保证本课题的顺利实施并取得高水平成果。

农药进入土壤环境后，能够与有机质和矿物等土壤组分相互作用，从而生成结合态，影响其在土壤中的生物可利用性及其毒性。本项目对土壤结合态农药的生物可利用性及其潜在毒性展开了研究，包括农药结合态的生成及其表征、农药的植物可利用性及其毒性、结合态农药的动物可利用性及其毒性、农药及其代谢物混合毒性等。首先研究了SOM的覆盖作用对碳基材料吸附农药和重金属的影响，建立了碳基材料吸附敌草隆和Pb(II)与SOM含量的定量关系，可以直接由SOM含量预测敌草隆和Pb(II)的吸附容量。研究了硝基芳香化合物与蒙脱石的相互作用及其影响因素，提出了两者相互作用生成结合态的主导机制。研究了麦苗吸收4-氯-3-甲基苯酚的规律及毒性效应，结合观察到的麦苗细胞膜通透性变化，提出了主要毒性作用机制及其对后续吸收的抑制作用。通过测定麦苗对富勒烯的吸收规律，并观察富勒烯颗粒在麦苗体内对细胞的挤压损坏作用和对细胞膜通透性的改变，提出了富勒烯对麦苗的损伤机制及影响共存林丹的吸收机制。测定了老化时间对蚯蚓吸收分布和释放结合态林丹的影响；基于de novo RNA测序，对蚯蚓基因组变化进行了分析，结合林丹暴露后蚯蚓体内神经递质含量的变化及蚯蚓运动活性的测试结果，证明了结合态林丹对蚯蚓仍然具有明显的毒性。为研究农药及其代谢物的混合毒性，建立了农药混合物的毒性评估与预测方法，包括农药对土壤线虫急性致死毒性的微板分析方法、多元混合物体系毒性评估的一般方法以及三角剖分插值法预测农药混合物毒性的新方法，据此评价及预测了1)农药及混合物对野生型秀丽线虫的急性致死毒性和2)农药及混合物对转基因品系秀丽线虫及青海弧菌的毒性。迄今发表27篇论文、一件专利。培养毕业六名博士生和六名硕士生，多名博士生和硕士生在读。参加国际学术会议六人次、国内会议八人次。

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