A Biotic Ligand Model for Phytotoxicity of Rare Earth Elements in Mixture

混合物中稀土元素植物毒性的生物配体模型

• 批准号: RGPIN-2019-05011
• 负责人: Hale, Beverley
• 金额: $ 3.42万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=753360
• 关键词: Biotic; Ligand; Model; Phytotoxicity; Rare

Concentrations of rare earth elements (REEs) are increasing in the St. Lawrence River, resulting from agricultural runoff, from which increased soil concentrations in the St. Lawrence basin soils can be inferred. As soil pH is lower in eastern Canadian soils than in western Canada, the potential for toxicity of REEs in soil is growing, and the additional risk of REE mixtures to soil-dwelling biota, unknown. Cerium (Ce), Lanthanum (La), Neodymium (Nd), Samarium (Sm) are light REEs (LREEs) which are taken up by plants as divalent ions but may be translocated as trivalent ions. As trivalent cations, the lanthanides are thought to displace the divalent Ca from extra- and intra-cellular binding sites, with La being characterized as super-calcium. The nutrient effects of REEs on plants include increased photosynthesis and thus yield, enhanced uptake and utilization of nutrients, enhanced respiration and uptake of water and increased tolerance to stress. The first objective of the proposed work is to expand the knowledge of REE toxicity thresholds for terrestrial plants and endpoints. These thresholds will be determined in multiple soils that range in pH, effective cation exchange capacity (eCEC) and major soil cations, factors that are expected to vary the toxicity of REEs. These thresholds will be determined for both single metal and mixtures using two different types of concentration ratios: equitoxic (using the effect concentrations derived from single metal studies) and environmental (based on crustal and mining waste data). The REE mixtures responses will be characterized using a suite of statistical models that identify whether the responses follow concentration addition, response addition or a general linear model. These data will create the potency factors for the individual REEs. The data will also create testable hypotheses of how REE speciation and movement in the soil might be modifying the nominal exposure of plants to REE mixtures. The second objective is to explore these testable hypotheses of REE behavior in the soil by identifying the relationships among soil characteristics, bioaccessible REEs in soils, and tissue concentrations using batch extraction, DGT devices and geochemical speciation modelling software. The third objective is to integrate the data from the first two objectives into a BLM-type framework for plant toxicity that can be applied to REEs in soil, singly or in mixture, such as WHAM-FTOX. This will include the solution speciation of the REEs as modified by soil characteristics, competition among REEs and between REEs and other soil cations, for the biotic ligand, and how diffusive and bulk transport through the soil-plant continuum might modify exposure. The data from this project will be of practical use to Canadian regulators to inform soil quality guidelines for REEs. The data will also advance fundamental knowledge of soil metal toxicity to plants for elements that are trivalent in solution.

由于农业径流，圣劳伦斯河中稀土元素 (REE) 的浓度正在增加，由此可以推断圣劳伦斯盆地土壤中的土壤浓度增加。由于加拿大东部土壤的 pH 值低于加拿大西部，土壤中稀土元素的潜在毒性正在增加，而稀土元素混合物对土壤生物群的额外风险尚不清楚。铈 (Ce)、镧 (La)、钕 (Nd)、钐 (Sm) 是轻稀土元素 (LREE)，它们以二价离子形式被植物吸收，但可能以三价离子形式转移。作为三价阳离子，镧系元素被认为可以取代细胞外和细胞内结合位点的二价 Ca，而 La 则被认为是超钙。稀土元素对植物的营养作用包括增加光合作用，从而提高产量、增强养分的吸收和利用、增强呼吸和水的吸收以及增强对胁迫的耐受性。拟议工作的第一个目标是扩大对陆地植物 REE 毒性阈值和终点的了解。这些阈值将在多种土壤中确定，范围包括 pH、有效阳离子交换能力 (eCEC) 和主要土壤阳离子，这些因素预计会改变 REE 的毒性。将使用两种不同类型的浓度比来确定单一金属和混合物的这些阈值：等毒性（使用来自单一金属研究的效应浓度）和环境（基于地壳和采矿废物数据）。 REE 混合物响应将使用一套统计模型来表征，这些模型确定响应是否遵循浓度加法、响应加法或一般线性模型。这些数据将为各个 REE 创建效力因子。这些数据还将创建可测试的假设，说明土壤中的稀土元素形态和运动如何改变植物对稀土混合物的名义暴露量。第二个目标是通过使用批量提取、DGT 设备和地球化学形态建模软件确定土壤特征、土壤中可生物利用的 REE 和组织浓度之间的关系，探索土壤中 REE 行为的可检验假设。第三个目标是将前两个目标的数据整合到 BLM 型植物毒性框架中，该框架可应用于土壤中的 REE（单独或混合），例如 WHAM-FTOX。这将包括受土壤特性影响的稀土元素的溶液形态、稀土元素之间以及稀土元素与其他土壤阳离子之间对于生物配体的竞争，以及通过土壤-植物连续体的扩散和批量传输如何改变暴露。该项目的数据将为加拿大监管机构提供实际用途，为稀土元素的土壤质量指南提供信息。这些数据还将增进关于溶液中三价元素对植物的土壤金属毒性的基础知识。