Biology, The Life Science Center, School of Science and Technology, Örebro University, Örebro, Sweden.
Chemistry, MTM, School of Science and Technology, Örebro University, Örebro, Sweden.
J Appl Toxicol. 2022 Sep;42(9):1510-1523. doi: 10.1002/jat.4319. Epub 2022 Mar 21.
Zinc is an essential trace metal required for the maintenance of multiple physiological functions. Due to this, organisms can experience both zinc deficiency and toxicity. Hardness is recognized as one of the main modifying physiochemical factors regulating zinc bioavailability. Therefore, the present study analyzed the effect of hardness on zinc toxicity using Daphnia magna. Endpoint parameters were acute-toxicity, development, reproduction, and expression data for genes involved in metal regulation and oxidative stress. In addition, the temporal expression profiles of genes during the initiation of reproduction and molting were investigated. Water hardness influenced the survival in response to exposures to zinc. A zinc concentration of 50 μg/l in soft water (50 mg CaCO /L) caused 73% mortality after 96 h exposure, whereas the same zinc concentration in the hardest water did not cause any significant mortality. Moreover, increasing water hardness from 100 to 200 mg CaCO /L resulted in a reduced number of offspring. Fecundity was higher at first brood for groups exposed to higher Zn concentrations. The survival data were used to assess the precision of the bioavailability models (Bio-met) and the geochemical model (Visual MINTEQ). As the Bio-met risk predictions overestimated the Zn toxicity, a competition-based model to describe the effects of hardness on zinc toxicity is proposed. This approach can be used to minimize differences in setting environmental quality standards. Moreover, gene expression data showed that using the toxicogenomic approach was more sensitive than the physiological endpoints. Therefore, data presented in the study can be used to improve risk assessment for zinc toxicity.
锌是维持多种生理功能所必需的微量元素。因此，生物体既可能缺锌，也可能锌中毒。水的硬度被认为是调节锌生物利用度的主要理化因素之一。因此，本研究采用大型溞（Daphnia magna）分析了硬度对锌毒性的影响。终点参数为急性毒性、发育、繁殖以及参与金属调控和氧化应激的基因的表达数据。此外，还研究了在繁殖和蜕皮开始时基因的时间表达谱。水的硬度会影响对锌暴露的生存能力。在软水（50mg CaCO3/L）中，锌浓度为 50μg/l 时，暴露 96 小时后导致 73%的死亡率，而在最硬的水中，相同的锌浓度则没有导致任何显著的死亡率。此外，水硬度从 100 增加到 200mg CaCO3/L 会导致后代数量减少。暴露于较高 Zn 浓度的组中，第一窝的繁殖力更高。生存数据用于评估生物利用度模型（Bio-met）和地球化学模型（Visual MINTEQ）的精度。由于 Bio-met 风险预测高估了锌的毒性，因此提出了一种基于竞争的模型来描述硬度对锌毒性的影响。这种方法可用于最小化设定环境质量标准的差异。此外，基因表达数据表明，使用毒理基因组学方法比生理终点更敏感。因此，本研究中提供的数据可用于改进锌毒性的风险评估。
