Organophosphorus pesticide (OPP) pollutants in the environment pose toxicity risks to living organisms, and the possible toxicity mechanism needs to be further clarified. Therefore, the individual and combined toxicity of three OPPs namely acephate (ACE), trichlorfon (TRI) and glyphosate (GIY) towards a freshwater green alga Chlorella pyrenoidosa (C. pyrenoidosa) was investigated by the time-dependent microplate toxicity analysis method. Here, a ternary mixture system of the three OPPs including five rays with different concentration ratios was designed by the uniform design ray method. The standard additive reference model, concentration addition (CA), was used to analyse toxicity interaction within ternary mixtures and the toxicity interaction intensity was characterized using a deviation from CA model (dCA). Besides, the effects of the three OPPs and their mixtures on the chlorophyll (CHL) content, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content of C. pyrenoidosa were also investigated to explore the possible mechanisms. The results show that toxicity of the three pesticides and their ternary mixture rays is time-dependent and the combined toxicity correlates well with the components, ACE and GLY. It is likely that there is a significant time-dependent synergism in ternary mixtures induced by ACE and GLY. The synergism intensity of the ternary mixtures is not more than 30% at the whole experimental concentration level. The CHL reduction rate and MDA content of C. pyrenoidosa increase, while the SOD activity of C. pyrenoidosa decreases with the lengthening of exposure time under the action of the three pesticides and their ternary mixtures. So, the possible mechanism of the three pesticides and their mixtures may be by affecting the photosynthesis, and then causing oxidative damage to C. pyrenoidosa cells. The results can provide reference for the combined toxicity assessment of OPPs to living organisms.

中文翻译：

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三种有机磷农药混合物中的协同作用对小球藻的定量评估和毒性机理。

环境中的有机磷农药（OPP）污染物对生物体具有毒性危险，因此可能的毒性机理有待进一步阐明。因此，三种OPP对乙酰氯小球藻（C. pyrenoidosa）的毒副作用分别为乙酰甲酸盐（ACE），敌百虫（TRI）和草甘膦（GIY）。通过时间依赖性微孔板毒性分析方法进行了研究。在此，通过均匀设计射线法，设计了5种浓度比不同的5种射线的3种OPP的三元混合系统。使用标准添加剂参考模型浓度添加（CA）来分析三元混合物中的毒性相互作用，并使用与CA模型（dCA）的偏差来表征毒性相互作用强度。此外，三个有机磷对叶绿素（CHL）含量的影响和它们的混合物，超氧化物歧化酶（SOD）活性和丙二醛（MDA）的含量小球藻还研究了可能的机制。结果表明，三种农药及其三元混合物射线的毒性是随时间变化的，并且组合毒性与ACE和GLY组分具有很好的相关性。ACE和GLY诱导的三元混合物中可能存在明显的时间依赖性协同作用。在整个实验浓度水平下，三元混合物的协同强度不超过30％。在CHL缩小率和MDA含量小球藻增加，而SOD活性蛋白核小球藻在三种农药及其三元混合物的作用下，随着暴露时间的延长而减少。因此，这三种农药及其混合物的可能机制可能是通过影响光合作用，然后对C. pyrenoidosa细胞造成氧化损伤。研究结果可为OPPs对活生物体的综合毒性评估提供参考。