Advancing non-invasive geoelectrical methods for imaging soil and groundwater contaminants

土壤和地下水受到危险化学品的污染，包括氯化溶剂和煤焦油（称为致密非水相液体）和其他人为化学品，如全氟烷基和多氟烷基物质，仍然是世界范围内的一个严重问题。仅在加拿大就有大约24000个联邦污染地点，包括以前的工业用地、退役的炼油厂和废弃的加油站。2019年，《联邦污染场地行动计划》延长了15年，联邦政府承诺在前五年（2020年至2024年）投入11.6亿美元。其中10.5亿美元用于修复污染场地。成功的修复需要准确了解污染物的位置，以及清除污染物的速度。由于常规方法（包括钻孔和监测井）具有侵入性、成本高且提供的信息有限，因此非常需要能够提供地下连续信息的快速、经济有效的方法。地电技术是一种非侵入性成像方法，可以“看到”地表以下，就像核磁共振成像扫描一样，探测到感兴趣的特征。这些技术，包括电阻率层析成像（ERT）和感应极化（IP），在环境调查中的应用越来越多。由于它们测量电学性质的空间变化，并且污染物通常相对于地下水具有不同的电学性质（即电阻性DNAPL，导电性AMD），因此地电技术作为污染地点的调查工具具有突出的潜力。然而，它们的普遍应用尚未实现，部分原因是缺乏解释地下非均质污染物分布的地电响应的工具和经验。本研究计划的最终目标是建立地电技术作为现场验证的污染现场调查工具，包括表征和修复活动。ERT是最成熟的技术，但需要进行关键的研究才能进入中试规模的现场试验。IP是一种更新且令人兴奋的技术，但需要基础工作来证明其对某些污染物和场景的价值。在短期内，该研究计划将集中于：(1)建立IP作为污染地点测绘技术的基础，(2)将ERT的初步成功转化为试点测试领域的实施，以及(3)启动测绘关键新兴污染物的地电技术。该计划是及时的，并补充了最近发生在地电成像方面的变革性改进。预计它将成为修复行业的游戏规则改变者，为加拿大的环境和经济带来重大利益。此外，它将培养3名MESc学生，2名博士生和5名本科生，并为快速发展的环境部门的关键职位做好准备。

Contamination of soil and groundwater by hazardous chemicals, including chlorinated solvents and coal tar (known as dense nonaqueous phase liquids (DNAPLs)) and other anthropogenic chemicals such as per- and polyfluoroalkyl substances (PFAS), remains a serious problem worldwide. Approximately 24,000 federal contaminated sites exist in Canada alone, including former industrial lands, decommissioned refineries, and abandoned gas stations. In 2019, the Federal Contaminated Sites Action Plan was renewed for 15 years, with the federal government pledging $1.16 billion for the first five years (2020 to 2024). Of this, $1.05 billion has been assigned to remediate contaminated sites. Successful remediation requires accurate knowledge on where the contaminants are, and how quickly they are being removed. Since conventional methods, including boreholes and monitoring wells, are intrusive, costly and provide limited information, rapid and cost-effective methods providing continuous information on the subsurface are highly desirable. Geoelectrical techniques are non-invasive imaging methods that can `look' below the surface, much like an MRI scan, to detect features of interest. These techniques, which include electrical resistivity tomography (ERT) and induced polarization (IP), are seeing increasing application in environmental investigations. Since they measure the spatial variation of electrical properties, and contaminants typically have distinct electrical properties relative to groundwater (i.e., resistive DNAPL, conductive AMD), geoelectrical techniques have outstanding potential as investigative tools at contaminated sites. However, their common application has not been realized, due in part to the lack of tools and experience in interpreting geoelectrical responses from heterogeneous contaminant distributions in the subsurface. The ultimate goal of this research program is to establish geoelectrical techniques as field-proven tools for contaminated site investigations, including characterization and remediation activities. ERT is the most mature technique but requires critical research to jump to pilot-scale field trials. IP is newer and exciting but needs fundamental work to prove its value for certain contaminants and scenarios. In the short-term, this research program will focus on: (i) building the foundation for IP as a technique for mapping contaminated sites, (ii) translating initial success of ERT to pilot test field implementation, and (iii) launching geoelectrical techniques for mapping key emerging contaminants. The program is timely and is supplemented by the recent, transformative improvements occurring in geoelectrical imaging. It is expected to be a game changer in the remediation industry, leading to significant benefits to the Canadian environment and economy. Furthermore, it will train 3 MESc students, 2 PhD students and 5 undergraduate students and prepare them for key positions in the fast-growing environmental sector.