School of Environmental Science and Engineering, Shanghai Jiao Tong University, 200240 Shanghai, China.
School of Geographic Sciences, East China Normal University, 200241 Shanghai, China.
Sci Total Environ. 2020 Nov 25;745:140926. doi: 10.1016/j.scitotenv.2020.140926. Epub 2020 Jul 17.
Arsenic, copper, and zinc are common elements found in contaminated soils but little is known about their combined effects on plants when presented simultaneously. Here, we systematically investigated the phytotoxicity and uptake of binary and ternary mixtures of As, Cu, and Zn in a soil-plant system, using wheat (Triticum aestivum) as model species. The reference models of concentration addition (CA) and response addition (RA) coupled with different expressions of exposure (total concentrations in soil ([M], mg/kg), free ion activities in soil solution ({M}, μM), and internal concentrations in plant roots ([M], μg/g)), were selected to assess the interaction mechanisms of binary mixtures of AsCu, AsZn, and CuZn. Metal(loid) interactions in soil were estimated in terms of solution-solid partitioning, root uptake, and root elongation effects. The partitioning of one metal(loid) between the soil solution and solid phase was most often inhibited by the presence of the other metal(loid). In terms of uptake, inhibitory effects and no effects were observed in the mixtures of As, Cu, and Zn, depending on the mixture combinations and the dose metrics used. In terms of toxicity, simple (antagonistic or synergistic) and more complex (dose ratio-dependent or dose level-dependent) interaction patterns of binary mixtures occurred, depending on the dose metrics selected and the reference models used. For ternary mixtures (As-Cu-Zn), nearly additive effects were observed irrespective of dose descriptors and reference models. The observed interactions in this study may help to understand and predict the joint toxicity of metal(loid)s mixtures in soil-plant system. Mixture interactions and bioavailability should be incorporated into the regulatory framework for accurate risk assessment of multimetal-contaminated sites.
砷、铜和锌是污染土壤中常见的元素，但对于它们同时存在时对植物的综合影响知之甚少。在这里，我们使用小麦（Triticum aestivum）作为模型物种，系统地研究了土壤-植物系统中砷、铜和锌二元和三元混合物的植物毒性和吸收。选择浓度加和（CA）和响应加和（RA）参考模型，并结合不同的暴露表达（土壤中的总浓度 ([M]，mg/kg)、土壤溶液中的游离离子活性 ({M}，μM) 和植物根部的内部浓度 ([M]，μg/g))，以评估 AsCu、AsZn 和 CuZn 二元混合物的相互作用机制。通过溶液-固相分配、根系吸收和根系伸长效应来评估金属（类）在土壤中的相互作用。一种金属（类）在土壤溶液和固相之间的分配通常受到另一种金属（类）的存在的抑制。在吸收方面，根据混合物组合和使用的剂量指标，观察到 As、Cu 和 Zn 混合物存在抑制作用和无影响。在毒性方面，根据所选剂量指标和参考模型，二元混合物会出现简单（拮抗或协同）和更复杂（剂量比依赖性或剂量水平依赖性）的相互作用模式。对于三元混合物（As-Cu-Zn），无论剂量描述符和参考模型如何，几乎都观察到相加效应。本研究中观察到的相互作用有助于理解和预测土壤-植物系统中金属（类）混合物的联合毒性。应将混合物相互作用和生物利用度纳入多金属污染场地的监管框架，以进行准确的风险评估。
