Transport of toxic metals in clay mineral barriers:Influences of mobile sorbent nanoparticles

垃圾填埋场渗滤液和受污染的土地孔隙水含有多种污染物，如异种有机化合物（如芳香族卤化烃）和潜在有毒金属（如铬、砷和镉）。最广泛使用的控制这些有毒物质的策略是通过使用低水力导电性粘土衬垫。这类系统的初始模型在很大程度上基于基于批吸附数据的溶质输运模型，其中物种被定义为在液相和固相之间划分。然而，很明显，胶体材料，也被称为移动吸附剂纳米颗粒（MSNs），在溶解的有机物和金属的运输中起着重要的作用。在评价msn对垃圾填埋场和受污染土地中有毒金属迁移的影响时，需要更多的定量数据，以便用于开发通用模型，以描述和预测潜在有毒物种在这些环境中的迁移。这将需要研究从不同年龄和管理方法的堆填渗滤液中提取的msn，以及在模拟堆填条件下对商业制造的具有特定尺寸、电荷和浓度的msn进行实验研究。粒径、电荷和浓度是影响粘土衬里材料对msn的过滤和过滤的关键属性，也是可以通过使用人造微球来控制的参数。因此，对人造纳米颗粒和粘土衬里之间的相互作用进行量化，可以阐明这些参数对msn促进或阻止污染物跨屏障传输的潜力的影响，从而提供一种更准确预测容器失效的方法。从这些研究中获得的数据是开发对污染场地有毒金属行为进行准确和精确预测所需模型的绝对先决条件，从而开发出可靠和具有成本效益的策略，以确保填埋场实践符合立法要求，特别是欧盟地下水指令80/68/EEC和新的地下水子指令（2006/118/EC）中规定的要求。

Landfill leachates and contaminated land pore waters contain a wide range of pollutants, such as xenobiotic organic compounds (e.g. aromatic halogenated hydrocarbons) and potentially toxic metals (e.g. Cr, As, and Cd). The most widely used strategy for containing these toxic substances is through the use of low hydraulic conductivity clay liners. Initial models of such systems were largely predicated on solute transport models based on batch sorption data, in which species were defined as partitioned between liquid and solid phases. It is apparent, however, that colloidal materials, also termed as mobile sorbent nanoparticles (MSNs), play an important role in transport of dissolved organic matter and metals.In evaluating the impact of MSNs on toxic metal transport in landfills and contaminated land, there is a need for more quantitative data that can be used to develop generic models to describe and predict the transport of potentially toxic species in these environments. This will require study of MSNs derived from landfill leachates of different ages and management practices, together with experimental study of commercially manufactured MSNs of defined size, charge and concentration under simulated landfill conditions. Size, charge and concentration are the key attributes influencing straining and filtering of MSNs by clay liner materials and are parameters that can be manipulated through the use of manufactured microspheres. Quantification of interactions between manufactured nanoparticles and clay liners thus permits elucidation of the effects of these parameters on the potential for MSNs to facilitate or prevent cross-barrier transport of contaminants, therefore providing a means through which containment failure can be more accurately predicted. The data derived from these studies are an absolute pre-requisite for developing the models required to make accurate and precise predictions of toxic metal behaviour in contaminated sites, and thus develop robust and cost-effective strategies for ensuring compliance of landfill practice with legislative requirements, in particular those set out in EU Groundwater Directive 80/68/EEC and the new Groundwater Daughter Directive (2006/118/EC).