Silver interactions with dissolved organic matter: Importance of reduced sulfur and implications for aquatic toxicity mitigation

银可能是个人护理产品(肥皂、洗发水、除臭剂等)对环境的潜在输入例如由联合利华和联合利华加拿大公司在全球制造和分销的产品。能够理解和预测排放到环境中的银的影响是很重要的。仅仅知道全银是不够的，因为不同形态的金属具有不同的潜在毒性。生物利用度方法在为水环境中的金属制定适当的保护标准方面是有用的。这些方法使用计算来预测总金属中有多少部分可与生物体结合并具有潜在的毒性。为了正确地完成银的生物利用度建模，首先需要填补一个数据空白。这一数据差距是对还原硫化物在银结合和最终毒性缓解中的作用的详细理解。众所周知，银与还原的硫化物配体结合很强，但在为风险评估目的对样品进行表征时，测量硫化物不是常规分析的一部分。即使有硫化物数据，目前也没有经过验证的计算机模型来从测量的水化学数据中估计生物有效性。因此，监管机构和排污者，如联合利华加拿大公司，还没有足够的信息或工具来对环境中的白银做出适当的管理决策。这项研究将为开发水生系统中银的预测工具提供必要的数据。为了实现这一点，现实世界中的样品将加入银，添加的自由形式的银的比例将通过离子选择电极来测定。利用这种实验方法，将对各种硫化物含量不同的样品产生所谓的结合等温线。这些等温线将在数学上符合银与表面和废水中的化合物结合的模型。生成的形态模型可以与现有的生物有效性实验相结合，并用于根据特定接收水的特性来预测水中银的安全水平。

Silver is potentially input to the environment from personal care products (soap, shampoo, deodorant, ...) such as those manufactured and distributed globally by Unilever and Unilever Canada. It is important to be able to understand and predict impacts of silver discharged into the environment. Just knowing total silver is not enough as different forms of a metal have different potential toxicity. Bioavailability approaches have been useful in setting appropriate and protective criteria for metals in aquatic environments. These approaches use calculations to predict what fraction of the total metal is available to bind to organisms and potentially be toxic. To properly accomplish bioavailability modelling for silver, there is a data gap that needs to be filled first. This data gap is a detailed understanding of the role of reduced sulfide in silver binding and ultimately toxicity mitigation. It is well understood that silver binds strongly to reduced sulfide ligands but measuring sulfide is not part of routine analysis when characterizing samples for risk assessment purposes. Even with sulfide data, there do not currently exist validated computer models to estimate bioavailabilty from measured water chemistry data. Thus regulators and dischargers, such as Unilever Canada, do not yet have sufficient information or tools to make appropriate management decisions for silver in the environment. This research will provide data necessary to develop predictive tools for silver in aquatic systems. To accomplish this real world samples will have silver added to them and the fraction of added silver in the free form will be deterimined by ion selective electrode. Using this experimental approach so-called binding isotherms will be generated for a variety of samples of variable sufide content. These isotherms will be mathematically fit to models for silver binding to compounds occuring in surface as well as waste waters. The resultant speciation model can be coupled with existing bioavailability experiments and used to predict safe levels for silver in water depending on characteristics of the specific receiving water.