Despite the co-occurrence of metals in aquatic environments, their joint effects are generally not considered during risk assessments. Data on the combined effects of zinc (Zn) and aluminum (Al) on aquatic animals are extremely scarce in the literature, although these metals are commonly used in domestic and industrial activities. In the present study, we investigated the effects of mixtures of Zn and Al on the cladoceran Ceriodaphnia silvestrii. We evaluated immobility (at 48 h) and ingestion rates (at 24 h). We also performed chronic toxicity tests for single metals. The environmental risks of these substances for tropical freshwaters were estimated from the risk quotient (measured environmental concentration/predicted no-effect concentration). In immobility tests, our results showed a 48-h median effect concentration (EC50) of 0.22 mg Zn L⁻¹ and 0.52 mg Al L⁻¹, and we observed synergistic effects of Zn and Al, following the independent action model. The ingestion rates of C. silvestrii were inhibited at 0.1, 0.4, and 0.5 mg Al L⁻¹, and they were increased at 0.08 mg Zn L⁻¹; we observed antagonistic effects in all treatments combined with 0.5 mg Al L⁻¹. In terms of chronic toxicity, a 7-d EC50 occurred at 0.11 mg Zn L⁻¹ and 0.37 mg Al L⁻¹. The risk assessment suggests a potential risk of these metals at environmentally relevant concentrations, especially when in a mixture. Therefore, we recommend mixture toxicity tests during risk assessments to ensure that zooplankton are protected. Environ Toxicol Chem 2021;40:2912–2922. © 2021 SETAC

中文翻译：

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锌和铝混合物对 Ceriodaphnia silvestrii（甲壳纲：枝角类）的毒性和风险评估

尽管金属在水生环境中同时存在，但在风险评估期间通常不考虑它们的联合影响。文献中关于锌 (Zn) 和铝 (Al) 对水生动物的综合影响的数据极为稀少，尽管这些金属通常用于家庭和工业活动。在本研究中，我们研究了 Zn 和 Al 混合物对枝角类Ceriodaphnia silvestrii的影响。. 我们评估了不动（48 小时）和摄取率（24 小时）。我们还对单一金属进行了慢性毒性测试。这些物质对热带淡水的环境风险是根据风险商（测量的环境浓度/预测的无影响浓度）估算的。在不动性测试中，我们的结果显示 48 小时的中位效应浓度 (EC50) 为 0.22 mg Zn L ^-1和 0.52 mg Al L ^-1，我们观察到 Zn 和 Al 的协同效应，遵循独立作用模型。C. silvestrii的摄取率在0.1、0.4和 0.5 mg Al L ^-1时受到抑制，在 0.08 mg Zn L ^-1时增加; 我们在所有处理中观察到与 0.5 mg Al L ^-1结合的拮抗作用。在慢性毒性方面，0.11 mg Zn L ^-1和 0.37 mg Al L ^-1发​​生 7 天 EC50 。风险评估表明这些金属在环境相关浓度下存在潜在风险，尤其是在混合物中时。因此，我们建议在风险评估期间进行混合物毒性测试，以确保浮游动物受到保护。环境毒物化学2021；40:2912–2922。© 2021 SETAC