Van Regenmortel Tina, Berteloot Olivier, Janssen Colin R, De Schamphelaere Karel A C
Faculty of Bioscience Engineering, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, Ghent, Belgium.
Environ Toxicol Chem. 2017 Oct;36(10):2781-2798. doi: 10.1002/etc.3840. Epub 2017 Jun 13.
Risk assessment in the European Union implements Zn bioavailability models to derive predicted-no-effect concentrations for Zn. These models are validated within certain boundaries (i.e., pH ≤ 8 and Ca concentrations ≥ 5mg/L), but a substantial fraction of the European surface waters falls outside these boundaries. Therefore, we evaluated whether the chronic Zn biotic ligand model (BLM) for Daphnia magna and the chronic bioavailability model for Pseudokirchneriella subcapitata could be extrapolated to pH > 8 and Ca concentrations < 5 mg/L. Results from D. magna experiments suggested that the BLM is not able to reflect the pH effect over a broad pH range (5.5-8.5). In addition, because of Ca deficiency of D. magna in the soft water tests, we cannot conclude whether the BLM is applicable below its Ca boundary. Results for P. subcapitata experiments showed that the bioavailability model can accurately predict Zn toxicity for Ca concentrations down to 0.8 mg/L and pH values up to 8.5. Because the chronic Zn BLM for D. magna could not be extrapolated beyond its validity boundaries for pH, a generalized bioavailability model (gBAM) was developed. Of 4 gBAMs developed, we recommend the use of gBAM-D, which combines a log-linear relation between the 21-d median effective concentrations (expressed as free Zn ion activity) and pH, with more conventional BLM-type competition constants for Na, Ca, and Mg. This model is a first step in further improving the accuracy of chronic toxicity predictions of Zn as a function of water chemistry, which can decrease the uncertainty in implementing the bioavailability-based predicted-no-effect concentration in the risk assessment of high-pH and low-Ca concentration regions in Europe. Environ Toxicol Chem 2017;36:2781-2798. © 2017 SETAC.
欧盟的风险评估采用锌生物有效性模型来推导锌的预测无效应浓度。这些模型在特定边界内（即pH≤8且钙浓度≥5mg/L）得到了验证，但欧洲很大一部分地表水超出了这些边界。因此，我们评估了大型溞的慢性锌生物配体模型（BLM）和斜生栅藻的慢性生物有效性模型是否可以外推到pH>8和钙浓度<5mg/L的情况。大型溞实验结果表明，BLM无法在较宽的pH范围（5.5 - 8.5）内反映pH效应。此外，由于在软水测试中大型溞缺钙，我们无法得出BLM在其钙边界以下是否适用的结论。斜生栅藻实验结果表明，生物有效性模型能够准确预测钙浓度低至0.8mg/L和pH值高达8.5时的锌毒性。由于大型溞的慢性锌BLM无法外推到其pH有效性边界之外，因此开发了一个通用生物有效性模型（gBAM）。在开发的4个gBAM中，我们建议使用gBAM-D，它结合了21天半数有效浓度（以游离锌离子活性表示）与pH之间的对数线性关系，以及更传统的BLM型钠、钙和镁竞争常数。该模型是进一步提高锌作为水化学函数的慢性毒性预测准确性的第一步，这可以降低在欧洲高pH和低钙浓度地区的风险评估中实施基于生物有效性的预测无效应浓度时的不确定性。《环境毒理学与化学》2017年；36:2781 - 2798。©2017 SETAC。
