Constantino C, Comber S D W, Scrimshaw M D
Atkins Limited, Chilbrook, Oasis Business Park, Eynsham, Witney, OX29 4AH, UK.
Biogeochemistry Research Centre, Plymouth University, Plymouth, PL4 8AA, UK.
Environ Sci Pollut Res Int. 2017 Mar;24(9):8363-8374. doi: 10.1007/s11356-016-8332-3. Epub 2017 Feb 7.
The shift toward bioavailability-based standards for metals such as copper and zinc not only improves the ecological relevance of the standard but also introduces significant complexity into assessing compliance. This study examined differences in the copper and zinc complexation characteristics of effluents from a range of different sewage treatment works and in relation to so-called 'natural' samples. This information is essential to determine whether the inclusion of effluent-specific complexation characteristics within the regulatory framework could enhance the environmental relevance of compliance criteria. The data show that for copper, binding affinity was not greater than that measured for materials derived from the receiving water environment, with a mean log K of between 4.4 and 5.15 and mean complexation capacity ranging from 38 to 120 μg/mg dissolved organic carbon (DOC) for effluents compared with a log K of 5.6 and complexation capacity of 37 μg/mg DOC for the Suwannee River fulvic acid. For zinc, however, effluents exhibited a much higher complexation capacity, with effluent means ranging from 3 to 23 μg/mg DOC compared with the Suwannee River fulvic acid, for which the complexation capacity could not be determined. Synthetic ligands in sewage effluent, such as ethylenediaminetetraacetic acid (EDTA), are implicated as contributing to these observed differences. This suggests that the current biotic ligand models for zinc might overstate the risk of harm in effluent-impacted waters. The data also show that the copper and zinc complexation characteristics of effluent samples obtained from the same sewage treatment works were less different from one another than those of effluents from other treatment works and therefore that sewage source has an important influence on complexation characteristics. The findings from this study support the case that the contribution to complexation from effluent-derived ligands could enhance the environmental relevance of bioavailability-based compliance criteria, in particular for zinc, owing to the additional complexation capacity afforded by effluent-derived ligands.
向基于生物可利用性的铜和锌等金属标准转变，不仅提高了该标准与生态的相关性，还在评估合规性方面引入了显著的复杂性。本研究考察了一系列不同污水处理厂排放的废水与所谓“天然”样品中铜和锌的络合特性差异。这些信息对于确定在监管框架中纳入特定于废水的络合特性是否能提高合规标准与环境的相关性至关重要。数据表明，对于铜而言，其结合亲和力不高于从受纳水环境中获取的物质所测得的亲和力，废水的平均log K在4.4至5.15之间，平均络合容量为38至120μg/mg溶解有机碳（DOC），而苏万尼河富里酸的log K为5.6，络合容量为37μg/mg DOC。然而，对于锌，废水表现出更高的络合容量，废水的平均值为3至23μg/mg DOC，而苏万尼河富里酸的络合容量无法确定。污水中的合成配体，如乙二胺四乙酸（EDTA），被认为是造成这些差异的原因。这表明当前锌的生物配体模型可能高估了受废水影响水体中的危害风险。数据还表明，从同一污水处理厂获得的废水样品中铜和锌的络合特性彼此之间的差异小于其他处理厂废水的差异，因此污水来源对络合特性有重要影响。本研究的结果支持这样一种观点，即来自废水的配体对络合的贡献可以提高基于生物可利用性的合规标准与环境的相关性，特别是对于锌，因为废水来源的配体提供了额外的络合容量。
