己唑醇对3种水生生物的毒性效应与环境暴露风险

Toxic effects and exposure risk assessment of hexaconazole to three aquatic organisms

[目的]明确己唑醇对水生生物的毒性与环境暴露风险。[方法]以斑马鱼、大型溞和羊角月牙藻作为受试生物,采用静态试验法分别进行了急性毒性试验,评价其毒性等级。根据己唑醇的理化性质、环境行为和水稻田间施药信息,分别利用Top-Rice模型预测了叶片生长期、分蘖期、拔节期和开花期进行首次用药后的地表水暴露浓度,结合急性毒性数据评估其环境暴露风险。[结果]25%己唑醇悬浮剂对斑马鱼、大型溞和羊角月牙藻的急性毒性50%致死/抑制效应浓度分别为2.58(96 h-LC_(50))、2.24(48 h-EC_(50))、3.70/1.92(72 h-ErC_(50)/EyC_(50))mg a.i./L,毒性等级为中毒。在最大田间推荐用药量75 g a.i./hm2下,施药次数越多,风险越大。每季水稻用药1次时,分蘖期用药对溞类的急性暴露风险商值RQ<1比例低于60%,风险不可接受;每季水稻用药2次时,分蘖期和开花期用药对鱼类和溞类的RQ<1比例低于60%,风险不可接受;每季水稻用药3次或4次后,在叶片生长期至开花期用药对鱼类和溞类的RQ<1的比例均低于60%,风险不可接受。[结论]己唑醇对3种水生生物具有中等毒性,在水稻生长的不同时期用药对水中鱼类和溞类存在一定的暴露风险,在使用时应注意防范水生态系统的破坏。在每季水稻的叶片生长期至开花期用药3次或4次时,对水生鱼类和溞类的急性暴露风险均不可接受,表明了多次用药对水生态系统的高风险性,在田间应用时应减少用药次数或增加施药间隔时间,以减少水生态系统的暴露风险。

[Aims]This study aims to determine the toxicity and environmental exposure risk of hexaconazole to aquatic organisms.[Methods]Brachydanio rerio,Daphnia magna and Pseudokirchneriella subcapitata were used as test organisms.The acute toxicity tests and toxicity grade evaluation were carried out by static test method.According to the physical and chemical properties,environmental behavior and field application information of hexaconazole,the Top-Rice model was used to predict the surface water exposure concentration after the first application at leaf development,tillering,stem elongation and flowering stage.Combined with acute toxicity data,the environmental exposure risk was evaluated.[Results]The 50%lethal/inhibitory effect concentrations of hexaconazole 25%suspension concentrate agent on B.rerio,D.magna and P.subcapitata were 2.58(96 h-LC_(50)),2.24(48 h-EC_(50))and 3.70/1.92(72 h-ErC_(50)/EyC_(50))mg a.i./L,respectively.The toxicity levels was medium.Under the maximum recommended dosage of 75 g a.i./ha,the more hexaconazole is applied,the greater the risk of exposure will be.When the hexaconazole was applied to rice once a season at tillering stage,the proportion of acute exposure risk quotient RQ<1 of Daphnia was less than 60%,and the risk was unacceptable.When the hexaconazole was applied to rice twice a season at tillering stage and flowering stage,the proportion of acute exposure risk quotient RQ<1 of fish and Daphnia was less than 60%,and the risk was unacceptable.When the hexaconazole was applied to rice three or four times a season from leaf development stage to flowering stage,the proportion of acute exposure risk quotient RQ<1 of fish and Daphnia was less than 60%,and the risk was unacceptable.[Conclusions]Hexaconazole has moderate toxicity to three aquatic organisms.When applied in different growth stages of rice,it has a certain exposure risk to fish and Daphnia in water.When using this pesticide,attention should be paid to prevent the damage of aquatic ecosystem.The acute exposure risk to aquatic fish and Daphnia was unacceptable when the pesticide was applied three or four times from the leaf development to flowering stage of rice,indicating that multiple hexaconazole applications have high risk to the aquatic ecosystem.When applied in the field,the application times should be reduced and the application interval should be increased to reduce the exposure risk of the aquatic ecosystem.