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（DNAPLs））和其他人为化学品，如全氟烷基和多氟烷基物质（PFAS），仍然是世界范围内的一个严重问题。仅在加拿大就有大约24,000个联邦污染地点，包括前工业用地、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）提供11.6亿美元。其中，10.5亿美元已用于修复受污染场地。成功的补救措施需要准确了解污染物的位置以及清除污染物的速度。由于包括钻孔和监测威尔斯的常规方法是侵入性的、昂贵的并且提供有限的信息，因此非常需要提供关于地下的连续信息的快速且成本有效的方法。地电技术是一种非侵入性成像方法，可以像核磁共振扫描一样“观察”地表以下，以探测感兴趣的特征。这些技术，其中包括电阻率层析成像（ERT）和激发极化（IP），看到越来越多的应用在环境调查。由于它们测量电特性的空间变化，并且污染物通常相对于地下水具有不同的电特性（即，电阻性DNAPL、导电性AMD），地电技术作为污染场地的调查工具具有突出的潜力。然而，它们的共同应用尚未实现，部分原因是缺乏解释地下异质污染物分布的地电响应的工具和经验。 这项研究计划的最终目标是建立地电技术作为污染场地调查，包括表征和修复活动的现场验证工具。ERT是最成熟的技术，但需要关键的研究才能进入中试规模的现场试验。知识产权是新的和令人兴奋的，但需要基础工作，以证明其对某些污染物和场景的价值。在短期内，这项研究计划将侧重于：（一）建立IP的基础，作为一种技术，用于映射污染的网站，（二）翻译ERT的初步成功试点测试现场实施，和（三）推出地电技术映射关键新兴污染物。 该计划是及时的，并补充了最近发生在地电成像的变革性改进。预计它将成为补救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，它将培训3名MESc学生，2名博士生和5名本科生，并为他们在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.