The Role of Gases in Groundwater Contamination and Remediation

地下水是一种重要的自然资源。大约有1000万加拿大人依赖地下水作为饮用水源。它也是地表水与深层区域系统之间的重要纽带，也是加拿大工业（包括农业、石油和天然气）的水源。我们地下水的质量受到污染的威胁。加拿大有成千上万个受污染的地点，其中许多是位于城市中心和海滨的棕地。清理这些地点的成本是巨大的，可能总计数百亿美元。地下气体在地下水污染中起着重要的作用，但往往被低估。例如，气体可以自然产生或通过修复技术产生，它们影响地下水的流动（通过降低渗透性）以及污染物的运输和反应（通过气体和地下水之间的质量传递）。气体本身也可能是污染物。例如，页岩气开采的迅速增加导致人们越来越关注环境影响，包括甲烷气体对饮用水含水层的污染。

Groundwater is a vital natural resource. Approximately 10 million Canadians rely on groundwater as a source of drinking water. It is also an important link between surface water and deeper regional systems, and is a source of water for Canadian industries, including agriculture and oil and gas. The quality of our groundwater is threatened by contamination. There are tens of thousands of contaminated sites in Canada, many of which are brownfield properties located in urban centres and along waterfronts. The cost to clean up these sites is substantial, and likely totals tens of billions of dollars. Gases in the subsurface play an important, but often underappreciated, role in groundwater contamination. For example, gases can be created naturally or by remediation technologies, and they affect the flow of groundwater (by reducing permeability) as well as the transport and reaction of contaminants (by mass transfer between the gas and groundwater). Gases can also be contaminants themselves. For example, the rapid increase in shale gas extraction has led to increased concern over environmental impacts, including the contamination of drinking water aquifers by methane gas. The proposed research will consist of a coordinated program of laboratory experiments (bench-scale columns and flow cells) combined with numerical modelling to investigate fundamental mechanisms across multiple disciplines. A team of five graduate students (two Doctoral and three Master's) will develop methods to inject dissolved gas or create trapped gas bubbles using chemical reactions to enhance clean-up technologies. They will also investigate the dissolution of methane in groundwater to better understand the effects of gas leakage during shale gas extraction, and will develop novel characterization methods for the laboratory and field. This research will: (a) Establish the scientific basis for new technologies to enhance groundwater clean-up using thermal remediation and gas emplacement; (b) Provide the detailed data required to validate advanced numerical models of contaminant transport in groundwater where gases are present; (c) Develop new techniques for measuring groundwater gases in the laboratory (based on high-resolution visualization) and the field (based on cryogenic coring); and (d) Train graduate students to tackle emerging problems in groundwater contamination and remediation. The results of this research will be used by both researchers and industry in Canada to improve the clean-up of contaminated sites, contribute to the development of best-practices for monitoring shale gas extraction, and help site investigators more accurately measure dissolved gases and gas bubbles in groundwater. Overall, these results will support the long-term research vision of improving our understanding of gas migration and mass transfer in contaminated groundwater systems.