两种除草剂与两种杀虫剂对蛋白核小球藻的联合毒性作用评估

Evaluation of joint toxicity of two herbicides and two insecticides on Chlorella pyrenoidosa

为探讨两类典型农药(除草剂与杀虫剂)对水生生物的联合毒性效应,以两种除草剂:氰草津(cyanazine,CYA)、敌草快(diquat,DIQ)和两种杀虫剂:敌百虫(dipterex,DIP)、杀线威(oxamyl,OXA)为研究对象,采用直接均分射线法(direct equipartition ray,EquRay)设计4组二元除草剂-杀虫剂混合物体系,应用时间毒性微板分析法(Time-dependent microplate toxicity analysis,t-MTA)系统研究目标化合物及其二元混合物体系对蛋白核小球藻(Chlorella pyrenoidosa)在不同暴露时间(12、24、28、72、96 h)的毒性效应,分别应用浓度加和(concentration addition,CA)模型、绝对残差(deviation from CA,dCA)模型和拓展等效线图法分析除草剂和杀虫剂对C.pyrenoidosa的联合毒性作用。结果表明,4种农药的毒性由强到弱依次为CYA>DIQ>OXA>DIP,且两种除草剂在48—96 h的半数效应浓度(EC50)值均比两种杀虫剂的EC50值高出1—2个数量级;3种模型对混合物的毒性作用评估基本一致,除草剂与杀虫剂二元混合物OXA-CYA、OXA-DIQ、DIP-CYA的毒性作用整体上呈现由加和作用向拮抗作用转变,DIP-DIQ则呈现由加和作用向较弱的协同作用转变,且各混合物体系的毒性作用都具有时间依赖性和浓度比依赖性;3个模型各有优缺点,CA是最经典的模型,可以直观地描述所有混合物毒性作用的动态变化规律,dCA模型可以定量描述混合物毒性作用的强度,拓展等效线图可以直观的描述两元混合物各组分间相互作用的浓度比依赖关系。

In order to explore the joint toxic effects of two typical pesticides(herbicide and insecticide)on aquatic organisms,two herbicides:cyanazine(CYA),diquat(DIQ)and two insecticides:dipterex(DIP)and oxamyl(OXA)were used as research objects,and the direct equipartition ray(EquRay)was used to design four groups of binary herbicide-insecticide mixture systems.The time-dependent microplate toxicity analysis(t-MTA)was used to study the effects of target compounds and binary mixture systems on Chlorella pyrenoidosa(C.pyrenoidosa)at different exposure times(12,24,28,72 and 96 h).Concentration addition(CA)model,deviation from CA(dCA)model and extended isobologram method were used to analyze the joint toxic effects of herbicides and insecticides on C.pyrenoidosa.The results showed that the order of toxicity of four pesticides was CYA>DIQ>OXA>DIP,and the median effect concentration(EC50)values of the two herbicides were 1—2 orders of magnitude higher than those of the two insecticides at 48—96 h.The toxicity interaction of mixtures evaluated by the three models was basically consistent.The combined toxicity of herbicide and pesticide binary mixtures OXA-CYA,OXA-DIQ and DIP-CYA showed a transformation from additive effect to antagonistic effect on the whole,while DIP-DIQ showed a transformation from additive effect to weak synergistic effect.The combined toxicity of each mixture system was time-dependent and concentration-ratio dependent.The three models have their own advantages and disadvantages.CA is the most classical model,which can intuitively describe the dynamic change rules of toxic effects of all mixtures,dCA model can quantitatively describe the toxicity interaction intensity of all mixtures,and the extended isobologram can more intuitively describe the concentration-ratio dependence of toxicity interaction between components of binary mixtures.