Assessing long-term impacts of chlorinated hydrocarbons to freshwater aquifers due to diffusive transport and reactions within clayey aquitards

评估由于粘土质弱透水层内的扩散迁移和反应而导致的氯化烃对淡水含水层的长期影响

• 批准号: RGPIN-2018-04634
• 负责人: Parker, Beth
• 金额: $ 3.72万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=661605
• 关键词: Assessing; long; term; impacts; chlorinated

Due to their widespread industrial usage, chlorinated hydrocarbons are among the most abundant groundwater contaminants across Canada and worldwide. After their release at the surface as dense non-aqueous phase liquids (DNAPLs), rapid vertical migration into the subsurface occurs due to their high density and low viscosity. During transport in the saturated zone, DNAPLs form pools on top of low permeability layers. With time, accumulated DNAPLs are transported by advection in the aquifer and by diffusion into the underlying low permeable units. After reduction of plume strength in the aquifer, back-diffusion occurs from the low permeability sediments that form a long-term contamination source for adjacent freshwater aquifers. ******Physical and reactive processes affecting chlorinated hydrocarbons in low permeability sediments are not yet fully understood. However, the identification and distinction of relevant processes affecting chlorinated hydrocarbons in low permeability zones is of major importance for estimating plume persistence in adjacent aquifers due to back-diffusion. This research program aims to gain a clear understanding of all physical and reactive processes affecting chlorinated hydrocarbons in saturated low permeability sediments and to assess their impact on long-term plume persistence in adjacent freshwater aquifers due to back-diffusion. The research will be conducted at three sites using advanced high-resolution field methods combined with new analytical methods as well as analytical and numerical modelling. Controlled release experiments are in progress at two sites in ongoing studies, which I initiated more than 15 years ago (near Sarnia and Alliston, ON). These sites are unique because physical and reactive processes can be investigated under controlled conditions, as the initial conditions of the contamination (spill time, volume, composition) are well known. Furthermore, the datasets obtained can be compared with previous investigations, offering the incomparable opportunity to gain understanding of the temporal resolution of physical and reactive processes in low permeability sediments under controlled conditions. The third site (near the city of Florence, SC, USA) offers a real-world scenario with mixed organic contaminants present over a longer time period (50 years). This research will improve prospects for predicting the time scales over which plume persistence due to back-diffusion occurs, and thereby provide an improved basis for remedial related site management decisions.

由于其广泛的工业用途，氯化碳氢化合物是加拿大和全世界最丰富的地下水污染物之一。它们在表面以致密非水相液体（DNAPLs）的形式释放后，由于它们的高密度和低粘度，会迅速垂直迁移到地下。在饱和区运移过程中，DNAPLs在低渗层顶部形成池。随着时间的推移，累积的DNAPLs在含水层中通过平流和扩散进入下伏的低渗透单元。含水层中羽流强度降低后，低渗透沉积物发生反扩散，对邻近淡水含水层形成长期污染源。******影响低渗透沉积物中氯化烃的物理和反应过程尚未完全了解。然而，识别和区分影响低渗透带氯代烃的相关过程对于估计邻近含水层中由于反扩散而产生的烟羽持久性具有重要意义。该研究项目旨在清楚地了解影响饱和低渗透沉积物中氯化烃的所有物理和反应过程，并评估它们对邻近淡水含水层中由于反向扩散而产生的长期羽流持久性的影响。这项研究将在三个地点进行，使用先进的高分辨率现场方法，结合新的分析方法以及分析和数值模拟。控制释放实验正在两个地点进行，这是我在15年前开始的研究（靠近萨尼亚和阿利斯顿，ON）。这些地点是独特的，因为物理和反应过程可以在受控条件下进行调查，因为污染的初始条件（泄漏时间、体积、成分）是众所周知的。此外，获得的数据集可以与以前的研究进行比较，为了解受控条件下低渗透沉积物的物理和反应过程的时间分辨率提供了无与伦比的机会。第三个地点（靠近美国南卡罗来纳州佛罗伦萨市）提供了一个真实的场景，其中混合有机污染物在较长时间（50年）内存在。这项研究将提高预测由于反向扩散而导致羽流持续发生的时间尺度的前景，从而为补救相关的现场管理决策提供改进的基础。