Increased focus on the development and application of bioavailability-based metal water quality guideline values requires increased understanding of the influence of water chemistry on metal bioavailability and toxicity. Development of empirical models, such as multiple linear regression models, requires the assessment of the influence of individual water quality parameters as toxicity-modifying factors. The present study investigated the effect of pH on the lability and toxicity of zinc (Zn) to a tropical green microalga (Chlorella sp.). Zinc speciation and lability were explored using the Windermere Humic Aqueous Model (WHAM7), ultrafiltration, and diffusive gradients in thin films (DGT). Zinc toxicity increased significantly with increasing pH from 6.7 to 8.3, with 50% growth inhibition effect concentrations decreasing from 185 to 53 µg l^–1 across the pH range. Linear relationships between DGT-labile Zn and dissolved Zn did not vary across the tested pH range, nor did the linear relationship between dissolved (<0.45 µm) and ultrafiltered (<3 kDa) Zn. Our findings show that Zn toxicity to this freshwater alga is altered as a function of pH across environmentally realistic pH ranges and that these toxicity changes could not be explained by Zn speciation and lability as measured by DGT and WHAM7. Environ Toxicol Chem 2021;40:2836–2845. © 2021 SETAC

中文翻译：

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pH 值对热带淡水微藻锌不稳定和毒性的影响

更加关注基于生物利用度的金属水质准则值的开发和应用需要更多地了解水化学对金属生物利用度和毒性的影响。开发经验模型，例如多元线性回归模型，需要评估单个水质参数作为毒性调节因素的影响。本研究调查了 pH 值对锌 (Zn) 对热带绿色微藻 ( Chlorella ) 的不稳定性和毒性的影响。sp。）。使用温德米尔腐殖质水模型 (WHAM7)、超滤和薄膜扩散梯度 (DGT) 探索了锌的形态和不稳定性。随着 pH 从 6.7 增加到 8.3，锌的毒性显着增加，在整个 pH 范围内，50% 的生长抑制效应浓度从 185 降低到 53 µg l ^{–1 。}DGT 不稳定 Zn 和溶解 Zn 之间的线性关系在测试的 pH 范围内没有变化，溶解 (<0.45 µm) 和超滤 (<3 kDa) Zn 之间的线性关系也没有变化。我们的研究结果表明，锌对这种淡水藻类的毒性随着环境实际 pH 值范围内的 pH 值而改变，并且这些毒性变化不能用 DGT 和 WHAM7 测量的 Zn 形态和不稳定性来解释。环境毒物化学2021；40:2836–2845。© 2021 SETAC