叠加污染条件下环境激素类农药联合作用对蚯蚓的复合生态毒性及机理研究

The combined pollution of environmental-hormone pesticides threatens seriously the soil ecosystem in China. The mixed pesticides of cypermethrin and chlorpyrifos are one of the most representative pesticides among the mixed pesticides that have been considered as environmental-hormone pesticides (Endocrine Disrupting Chemicals, which is abbreviated as EDCs). Understanding of their chemical characteristics and ecological effects will be helpful in recognition of the combined effects of the EDCs mixed pesticides, which is of great significance in the ecological risk evaluation and pollution control in relation to such pesticides. In the present study, the two EDCs pesticides, cypermethrin and chlorpyrifos, were chosen to investigate their possible ecological toxicity on earthworms (Amynthas corticis) under a multiple-time addition method which was used to simulate the accumulation process of individual and mixed pesticides in the soil. The aim is: 1) to compare toxicity effects on earthworms from all function levels such as DNA, growth and reproduction between the two methods of the multiple-time overlying and one-time addition; 2) to analyze the dose-effect relationship of the toxin-induced reactions on earthworms and the residues of cypermethrin and chlorpyrifos in soil and earthworms; 3) to clarify the integrated toxicity of individual and mixed pesticides on earthworms; and 4) to explore the mechanism of ecological effects of combined contamination with cypermethrin and chlorpyrifos on earthworms. The results from the present project will be very helpful to set up biological diagnosis for the target system and assessment of environment risk.

环境内分泌干扰物（EDCs）农药污染严重威胁我国的土壤生态系统安全。本课题选择我国应用较广的环境内分泌干扰物农药氯氰菊酯、毒死蜱为代表性污染物，采用叠加试验的方法模拟污染物在土壤中的逐渐累积过程，以云南耕地常见的蚯蚓优势种-皮质远盲蚓（Amynthas corticis）为实验生物，开展不同污染方式（一次污染与多次叠加污染）下两种农药单独及联合作用对蚯蚓的生态毒性差异研究；就两种农药单独及联合作用，对蚯蚓可能产生致毒作用的靶标酶、生殖系统内分泌干扰及遗传毒性进行分析；同时对此引发的蚯蚓行为变化、生理生化防御反应进行分析，研究叠加污染方式下土壤残留农药浓度、蚯蚓体内蓄积浓度与蚯蚓不同功能层次生态毒性指标之间的效应关系，揭示土壤氯氰菊酯、毒死蜱两种EDCs类农药联合叠加污染对蚯蚓的综合毒性作用，探讨EDCs类农药联合作用的复合生态毒性机制，为土壤EDCs类农药叠加污染累积的生态风险防治提供理论

土壤生态系统作为环境内分泌干扰物（EDCs）类农药的重要汇集地，EDCs农药污染严重威胁我国的土壤生态系统安全。本项目以EDCs农药氯氰菊酯、毒死蜱为代表性污染物，以云南耕地常见的蚯蚓优势种-皮质远盲蚓（Amynthas corticis）为实验生物，开展不同污染方式（一次污染与多次叠加污染）下两种农药单独及联合作用对蚯蚓的生态毒性研究，就两种农药单独及联合作用，对蚯蚓可能产生致毒作用的靶标进行分析；同时对此引发的蚯蚓生理生化防御反应进行分析，探讨EDCs类农药联合作用对蚯蚓的复合毒性机制。研究结果表明：（1）毒死蜱、氯氰菊酯两种农药单独及联合作用在土壤中的降解存在差异。两种农药单独作用时，在土壤中的降解均符合单室模型C=C0e－kt，降解半衰期分别为 31.5d（氯氰菊酯） 和 57.8d（毒死蜱），联合作用时各组分农药在土壤中的降解过程符合双室模型 C=C1e－αt＋C2e－βt，不同阶段降解半衰期不同，氯氰菊酯前期和后期半衰期分别为 33.0d 和 53.3d ；而毒死蜱前期和后期的半衰期则分别为 63.0d 和 86.6d。与各农药单独作用相比，联合作用时各组分农药在土壤中降解速度变缓、滞留时间延长；（2）蚯蚓对不同污染方式进入土壤的实验农药的吸收蓄积存在差异，暴露 55d 时，蚯蚓对以一次污染方式进入土壤的氯氰菊酯的生物-土壤蓄积因子(FBSA)为 0.85~1.05，蚯蚓对以叠加污染方式进入土壤的氯氰菊酯的F BSA 为1.16~1.42。蚯蚓对以一次污染方式进入土壤的毒死蜱 FBSA为1.55~1.70，蚯蚓对以叠加污染方式进入土壤的毒死蜱的FBSA 为2.22~2.46。以叠加污染方式进入土壤的实验农药，更有利于蚯蚓对其进行生物富集，从而表现出较强的毒性；（3）与氯氰菊酯、毒死蜱单独作用相比，两种农药联合作用对蚯蚓具有显著的毒性增效效应。综合其它蚯蚓生态毒理学实验结果，认为实验农药联合作用对蚯蚓的毒性增效，可能与氯氰菊酯、毒死蜱对蚯蚓毒害的机制差异、神经系统的多靶位点交叉影响以及蚯蚓的防御过氧化酶系统损伤有关。本研究可为土壤EDCs类农药污染的生态风险防治提供依据。