CSIRO Land and Water, Private Bag No. 5, Wembley, WA, 6913, Australia; School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA, 6027, Australia.
CSIRO Land and Water, Private Bag No. 5, Wembley, WA, 6913, Australia; School of Earth Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.
Water Res. 2019 Jun 15;157:630-646. doi: 10.1016/j.watres.2019.04.001. Epub 2019 Apr 7.
Natural source zone depletion (NSZD) of light non-aqueous phase liquids (LNAPLs) includes partitioning, transport and degradation of LNAPL components. NSZD is being considered as a site closure option during later stages of active remediation of LNAPL contaminated sites, and where LNAPL mass removal is limiting. To ensure NSZD meets compliance criteria and to design enhanced NSZD actions if required, residual risks posed by LNAPL and its long term behaviour require estimation. Prediction of long-term NSZD trends requires linking physicochemical partitioning and transport processes with bioprocesses at multiple scales within a modelling framework. Here we expand and build on the knowledge base of a recent review of NSZD, to establish the key processes and understanding required to model NSZD long term. We describe key challenges to our understanding, inclusive of the dominance of methanogenic or aerobic biodegradation processes, the potentially changeability of rates due to the weathering profile of LNAPL product types and ages, and linkages to underlying bioprocesses. We critically discuss different scales in subsurface simulation and modelling of NSZD. Focusing on processes at Darcy scale, 36 models addressing processes of importance to NSZD are investigated. We investigate the capabilities of models to accommodate more than 20 subsurface transport and transformation phenomena and present comparisons in several tables. We discuss the applicability of each group of models for specific site conditions.
自然源区衰减（NSZD）包括轻非水相液体（LNAPL）的分配、传输和降解。NSZD 被认为是 LNAPL 污染场地主动修复后期阶段的一种场地关闭选择，并且在 LNAPL 质量去除受到限制的情况下。为了确保 NSZD 符合合规标准，并在需要时设计增强的 NSZD 措施，需要对 LNAPL 及其长期行为造成的剩余风险进行估计。预测长期 NSZD 趋势需要将物理化学分配和传输过程与建模框架内多个尺度上的生物过程联系起来。在这里，我们扩展并建立在最近关于 NSZD 综述的知识库基础上，以确定模拟 NSZD 长期趋势所需的关键过程和理解。我们描述了我们理解的关键挑战，包括产甲烷或好氧生物降解过程的主导地位、由于 LNAPL 产品类型和年龄的风化剖面，速率可能发生变化以及与潜在生物过程的联系。我们对 NSZD 的地下模拟和建模的不同尺度进行了批判性讨论。重点讨论达西尺度上的过程，研究了 36 个解决 NSZD 重要过程的模型。我们调查了模型容纳 20 多种地下传输和转化现象的能力，并在几个表中进行了比较。我们讨论了每组模型在特定场地条件下的适用性。
