Effective contaminant source geometries and their implications for final plume extension - ESTIMATE

致密非水相液体（DNAPL）污染物由于其在水中的溶解度极低且具有生物降解性，已被发现在地下水中持续存在数十年。由于DNAPLs还会造成巨大的环境和健康危害，因此需要对每个污染物场所进行适当的风险评估。到目前为止，已经进行了大量的调查（实地研究、实验室实验、分析和数值模拟），以表征地表下污染物的迁移、羽流内的运输以及控制反应过程。发现源带结构对稳态羽流扩展有显著影响，这是重要的评价性质。但是，不同的影响（即含水层性质、外部应力）与源区最终状态的相关性不能得到充分的澄清和量化。因此，需要关于污染源几何测量及其对影响的主要依赖的更多信息。复杂的源几何图形仅对单个场景有效，并且依赖于大量的进程。然而，在解析分析或数值分析中，由于时间和数据的限制，源几何结构大多被非常初级地纳入简单的几何结构。因此，为了改进污染物羽流的预测，需要直接有效的源几何形状来压缩信息，并从地下特性和外部应力中产生。有效的震源几何形状可以用来预测最终的羽流长度，其精度与复杂的震源几何形状相同。我们认为这是目前最关键的知识差距，限制了我们充分预测污染物羽流长度的能力。因此，我们希望描述含水层性质和外部应力对DNAPL源带结构的影响，这将使我们能够推导出转换技术，在考虑影响的情况下将复杂的源几何形状转换为有效的源几何形状。为了实现这一目标，我们将结合实验室规模的实验和数值模拟。我们的主要研究挑战是：(i)加强对复杂DNAPL源区结构最终范围的理解，（ii）量化外部应力和地点特定特征对复杂源区最终范围的影响，（iii）从复杂源几何形状中获得有效的源几何形状，（iv）提供外部应力和场地特定特征的函数关系，以获得有效的源几何形状，供分析或数值评估工具使用。基于羽流长度模型和源特征模型的结合，我们假设对源几何形状的改进描述将产生更好的最大羽流长度估计，因此，DNAPL修复技术有更好的机会。

Dense non-aqueous phase liquid (DNAPL) contaminants have been found to persist in groundwater bodies for several decades due to their very low solubility in water as well as biodegradation properties. A proper risk assessment of each contaminant site is required as DNAPLs additionally pose a tremendous environmental and health hazard.Up to now, numerous investigations (field studies, laboratory experiments, analytical and numerical modelling) were carried out in order to characterise sub-surface contaminant migration, transport within plumes, and governing reactive processes. Source zone architecture is found to have significant influence on steady-state plume extension, which is the critical assessment property. However, the relevance of different impacts (i.e. aquifer properties, external stresses) with respect to the final state of a source zone could not sufficiently be clarified and quantified. Hence, more information on geometric measures of a contaminant source and its major dependency on impacts are required. Complex source geometries are valid for a single scenario only, and depend on a large number of processes. However, in analytical or numerical analyses, source geometry is mostly incorporated very rudimentarily as simple geometrical structures due to time and data limitations. Therefore, straightforward effective source geometries that condense information, and emerge from sub-surface properties and external stresses are required for an improved prediction of contaminant plumes. Effective source geometries could be used to predict final plume lengths with same accuracy as complex source geometries. We consider this as the currently most critical knowledge gap that restricts our ability to adequately predict contaminant plume lengths. Therefore, we want to characterise the influence of aquifer properties and external stresses on DNAPL source zone architecture which will allow us to derive transformation techniques to convert complex to effective source geometries under consideration of impacts. To achieve this, we will utilize a combination of laboratory-scale experiments, and numerical modelling. Our main research challenges are to (i) enhance the understanding of the final extent of complex DNAPL source zone architectures, (ii) quantify the influence of external stresses and site-specific characteristics on the final extent of complex source zones, (iii) derive effective source geometries from complex source geometries, and (iv) provide a functional relationship of external stresses and site-specific characteristics to acquire effective source geometries for the use in analytical or numerical assessment tools. Based on a combination of a plume length model and a source characterisation model, we hypothesise that improved description of source geometries will yield better estimations of maximum plume length and, therefore, much better opportunities for DNAPL remediation techniques.