双唑草腈对3种水生生物的急性毒性及初级生态风险评估

为研究双唑草腈对水生生物的毒性和水体环境风险，在实验室条件下，以斜生栅藻、大型溞和斑马鱼为研究对象，分别采用OECD推荐的生长抑制法、活动抑制法、静态法和TOP-RICE模型，开展了双唑草腈的急性毒性试验和初级生态风险评估。结果表明:双唑草腈对斜生栅藻细胞增殖的72 h半数抑制效应浓度 (72 h-EC₅₀) 为1.44 × 10?2 mg/L，对大型溞活动的48 h半数抑制效应浓度 (48 h-EC₅₀) 为15.09 mg/L，对斑马鱼的96 h半数致死效应浓度 (96 h-LC₅₀) 为23.05 mg/L，根据我国《化学农药环境安全评价实验准则》中的毒性等级划分标准，相应毒性等级分别为高毒、低毒和低毒；在水生生态系统中，双唑草腈对脊椎动物和无脊椎动物的急性毒性风险商(RQ) 值小于1的分组占所有模拟场景的60%以上，超过60% 的分组对初级生产者的RQ值大于1，说明双唑草腈对大型溞和斑马鱼较为安全，对水生生态系统中脊椎动物和无脊椎动物的风险在可接受范围，但其对斜生栅藻毒性高，且对初级生产者的风险为不可接受。因此，生产中在施用双唑草腈时应避免药剂进入稻田周边水体，可通过减少农药使用量、合理调整施药时期等方法来减少双唑草腈对水生生态环境的风险，建议在早稻分蘖前期和晚稻分蘖后期使用。

Acute toxicities of pyraclonil to three aquatic organisms and its primary ecological risk assessment

In order to study the toxicity of herbicide pyraclonil to aquatic organisms and its risk to water environment, the acute toxicity of pyracllonil against three aquatic organisms such as Scenedesmus obliquus, Daphnia magna, and Brachydonio rerio were investigated under laboratory conditions using the alga growth inhibition, immobilization test and static test recommended by OECD, and its primary ecological risk was assessed based on TOP-RICE model. The results showed that the 72-hour median inhibitory concentration (72 h-EC₅₀) of pyraclonil on the proliferation of S. obliquus cells was 1.44 × 10?2 mg/L, and the 48-hour median inhibitory concentration (48 h-EC₅₀) on the activity of D. magna was 15.09 mg/L, and the 96-h medium lethal concentration (96 h-LC₅₀) on B. rerio was 23.05 mg/L. According to the classification standard of toxicity grades in "Chemical Pesticide Environmental Safety Evaluation Experiment Guidelines", the corresponding toxicity grades were high toxicity, low toxicity, and low toxicity respectively. In aquatic ecosystems, groups with an acute toxicity risk quotient (RQ) value less than 1 for pyraclonil to vertebrates and invertebrates accounted for more than 60% of all simulated scenarios, and more than 60% of groups had an RQ value greater than 1 for primary producers. The results indicated that pyraclonil is relatively safe for D. magna and B. rerio, and the risk to the vertebrates and the invertebrates in the aquatic ecosystem is acceptable, but its toxicity to S. obliquus is high, and the risk to primary producers is unacceptable. Therefore, the pyraclonil should be avoided from entering the water body around the paddy fields in the production process. The risk of pyraclonil to the aquatic ecosystem can be reduced by decreasing the amount of herbicide used and adjusting the application period reasonably. It is recommended to use pyraclonil at the early tillering stage of early rice or the late tillering stage of late rice.