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Abstract：
Copper at high concentrations is an ionoregulatory toxicant in fish and its toxicity is known to be strongly modulated by the water chemistry. The toxicity of Cu to the tropical fish cardinal tetra (Paracheirodon axelrodi) was investigated in waters from two major rivers of the Amazon watershed: the Rio Negro (filtered <0.45μm, pH 5.6, DOC=8.4 mgL-1, Na=33μM, Ca=8μM) and the Rio Solimões (filtered <0.45μm, pH 6.7, DOC=2.8 mgL-1, Na=185μM, Ca=340μM), as well as in a natural \"reference water\" (groundwater) which was almost DOC-free (pH 6.0, DOC=0.34 mgL-1, Na=53μM, Ca=5μM). Acute 96-h mortality, Cu bioaccumulation and net flux rates of Na+, Cl-, K+ and total ammonia were determined in P. axelrodi exposed in each water. Copper speciation in each water was determined by two thermodynamic models and by potentiometry, and its toxicity was predicted based on the biotic ligand model (BLM) framework. Our results indicate that high Na+ loss is the main mode of toxic action of Cu in P. axelrodi, in accordance with general theory. Cardinal tetra showed a particularly high ability to tolerate Cu and to maintain Na+ balance, similar to the ability of this and other endemic Rio Negro species to tolerate low pH and ion-poor conditions. Cu toxicity was lower in Rio Negro than in the other two waters tested, and the free [Cu2+] at the LC50, as determined by any of the three speciation methods tested, was approximately 10-fold higher. This variation could not be captured by a realistic set of BLM parameters. At least in part, this observation may be due to gill physiological alterations induced by the abundant dissolved organic matter of the Rio Negro. The implication of this observation is that, for metals risk assessment in tropical waters, similar to the Rio Negro, care must be used in applying BLM models developed using temperate DOC and temperate species.
摘要：
高浓度的铜是鱼中的离子调节毒物，已知其毒性受水化学的强烈调节。在亚马逊流域的两条主要河流的水域中，研究了铜对热带鱼红衣主教tetra（Parachirodonaxelrodi）的毒性：里约内格罗（过滤<0.45μm，pH5.6，DOC=8.4mgL-1，Na=33μM，Ca=8μM)和RoliSolimes(过滤<0.45μm，pH6.7，DOC=2.8mgL-1，Na=185μM，Ca=340μM),以及在几乎无DOC的天然“参考水”（地下水）中（pH6.0，DOC=0.34mgL-1，Na=53μM，Ca=5μM)。急性96小时死亡率，Cu的生物累积和Na+的净通量速率，Cl-,在暴露于每种水中的P.axelrodi中测定K+和总氨。每种水中的铜形态通过两种热力学模型和电位测定法确定，并基于生物配体模型(BLM)框架预测其毒性。我们的结果表明，高Na损失是铜在P.axelrodi中的主要毒性作用方式，根据一般理论。红衣主教tetra表现出特别高的耐受Cu和维持Na平衡的能力，类似于这种和其他特有的RioNegro物种耐受低pH值和离子贫乏条件的能力。RioNegro的铜毒性低于其他两个测试水域，以及通过测试的三种物种形成方法中的任何一种确定的LC50处的游离[Cu2+]，大约高10倍。这种变化不能被一组实际的BLM参数捕获。至少在某种程度上,这种观察可能是由于RioNegro丰富的溶解有机物引起的g生理变化。这个观察的含义是，用于热带水域的金属风险评估，类似于里约黑人，在应用使用温带DOC和温带物种开发的BLM模型时，必须格外小心。
