The US Environmental Protection Agency (USEPA) is reviewing the protectiveness of the national ambient water quality criteria (WQC) for nickel (Ni) and zinc (Zn) and compiling toxicity databases to update the WQC. An amphipod (Hyalella azteca) and a unionid mussel (Lampsilis siliquoidea) have shown high sensitivity to Ni and Zn in previous studies. However, there remained uncertainties regarding the influence of test duration (48 vs 96 h) and the presence and absence of food in acute exposures with the amphipod, and there were also concerns about poor control of amphipod growth and reproduction and mussel growth in chronic exposures. We conducted acute 48‐ and 96‐h water‐only toxicity tests to evaluate the influence of feeding and test durations on the toxicity of dissolved Ni and Zn to the amphipod; we also used recently refined test methods to conduct chronic Ni and Zn toxicity tests to evaluate the sensitivity of the amphipod (6‐wk exposure) and the mussel (4‐ and 12‐wk exposures). The 96‐h 50% effect concentrations (EC50s) of 916 µg Ni/L and 99 µg Zn/L from acute amphipod tests without feeding decreased from the 48‐h EC50s by 62 and 33%, respectively, whereas the 96‐h EC50s of 2732 µg Ni/L and 194 µg Zn/L from the tests with feeding decreased from the 48‐h EC50s by 10 and 26%, indicating that the presence or absence of food had apparent implications for the 96‐h EC50. Our chronic 6‐wk EC20s for the amphipod (4.5 µg Ni/L and 35 µg Zn/L) were 50 to 67% lower than the 6‐wk EC20s from previous amphipod tests, and our chronic 4‐wk EC20s for the mussel (41 µg Ni/L and 66 µg Zn/L) were similar to or up to 42% lower than the 4‐wk EC20s from previous mussel tests. The lower EC20s from the present study likely reflect more accurate estimates of inherent sensitivity to Ni and Zn due to the refined test conditions. Finally, increasing the chronic test duration from 4 to 12 wk substantially increased the toxicity of Zn to the mussel, whereas the 4‐ and 12‐wk Ni effect needs to be re‐evaluated to understand the large degree of variation in organism responses observed in the present study. Environ Toxicol Chem 2020;39:2256–2268. © 2020 SETAC

中文翻译：

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使用改进的测试方法评估镍和锌对2种敏感淡水底栖无脊椎动物的急性和慢性毒性。

美国环境保护局（USEPA）正在审查针对镍（Ni）和锌（Zn）的国家环境水质标准（WQC）的保护性，并编制毒性数据库以更新WQC。两栖纲（Hyalella azteca）和union贻贝（Lampsilis siliquoidea）在先前的研究中显示出对Ni和Zn的高度敏感性。但是，在两栖动物的急性接触中，测试时间的影响（48 vs 96 h）以及食物的存在与否仍然存在不确定性，并且对于长期接触中两栖动物的生长和繁殖以及贻贝的生长控制不佳也存在担忧。我们进行了急性48小时和96小时纯水毒性试验，以评估喂养和试验时间对溶解的镍和锌对两栖动物毒性的影响。我们还使用了最近改进的测试方法进行了慢性Ni和Zn毒性测试，以评估两足动物（6周暴露）和贻贝（4周和12周暴露）的敏感性。急性两栖动物试验的96 h 50％效应浓度（EC50s）为916 µg Ni / L和99 µg Zn / L，而从48 h EC50s分别降低了62％和33％，而96 h EC50s饲喂试验中的2732 µg Ni / L和194 µg Zn / L从48小时EC50下降了10％和26％，表明存在或不存在食物对96小时EC50都有明显影响。我们的两栖类慢性六周EC20（4.5 µg Ni / L和35 µg Zn / L）比以前的两栖类试验中的六周EC20低50％至67％，而我们的贻贝的慢性四周EC20则低（与之前的贻贝测试中的4周EC20相比，41 µg Ni / L和66 µg Zn / L）降低了42％。由于改进的测试条件，本研究中较低的EC20可能反映了对Ni和Zn固有敏感性的更准确估计。最后，2020年《环境毒理学》； 39：2256–2268。©2020 SETAC