Ferreira Daniel, Ciffroy Philippe, Tusseau-Vuillemin Marie-Hélène, Garnier Cédric, Garnier Jean-Marie
EDF, Division Recherche et Développement, Département Laboratoire National d'Hydraulique et Environnement, 6 Quai Watier, 78401 Chatou, France.
Chemosphere. 2009 Feb;74(8):1117-24. doi: 10.1016/j.chemosphere.2008.10.031. Epub 2008 Nov 29.
The present study investigated the effect of water cationic composition (Ca, Mg, Na, pH) on the bioaccumulation and elimination rates of copper by an aquatic moss (Fontinalis antipyretica), under laboratory conditions. For this purpose, mosses were exposed to copper at an environmentally relevant and usually non-toxic concentration (5 microg L(-1)) in natural waters where cationic composition and concentrations were varied. To describe copper bioaccumulation by aquatic mosses, a two-compartment model was the first-order kinetics, was developed and calibrated under a wide range of water cationic composition. Bioaccumulation rates of Cu in mosses were significantly reduced as the concentrations of competitive cations in solution increased. Hence, in hard-water, Ca and Mg cations play a protective role as they compete with Cu2+ ions for the absorption on transport sites at the organism-water interface. Based on the relationships between each major cation concentration and the exchange kinetics on mosses, the binding constants (K(Ci)(BL)) of each competing cations to the biological surfaces were derived. Using the present cationic-dependent kinetic model, it is now feasible to incorporate water cationic composition in the (re)interpretation of bryophytes contamination levels and in the (re)definition of Water Quality Criteria (WQC) as illustrated through two selected examples of biomonitoring programmes. In the framework of future national water quality guidelines revisions, a such flexible and mechanistic biomonitoring tool (integrating the protective effects of competing cations) may greatly improve the ability of regulators to derive site-specific Cu (metal) guidelines for protecting aquatic biota, while limiting the use of conservative assumptions.
本研究在实验室条件下，调查了水的阳离子组成（钙、镁、钠、pH值）对水生苔藓（扭口藓）铜生物累积和消除速率的影响。为此，将苔藓暴露于阳离子组成和浓度不同的天然水中，使其接触环境相关且通常无毒浓度（5微克/升）的铜。为描述水生苔藓对铜的生物累积，建立了一个两室模型，该模型基于一级动力学，并在广泛的水阳离子组成范围内进行了校准。随着溶液中竞争性阳离子浓度的增加，苔藓中铜的生物累积速率显著降低。因此，在硬水中，钙和镁阳离子起到保护作用，因为它们与铜离子竞争在生物体 - 水界面的转运位点上的吸收。基于各主要阳离子浓度与苔藓上交换动力学之间的关系，得出了各竞争性阳离子与生物表面的结合常数（K(Ci)(BL)）。通过两个选定的生物监测计划示例表明，利用当前的阳离子依赖动力学模型，现在可以将水阳离子组成纳入对苔藓植物污染水平的（重新）解释以及水质标准（WQC）的（重新）定义中。在未来国家水质指南修订的框架内，这样一种灵活且具有机制性（整合竞争性阳离子保护作用）的生物监测工具可能会极大地提高监管机构制定特定地点铜（金属）指南以保护水生生物群的能力，同时限制保守假设的使用。
