Long Term Field Experiments in Clayey Aquitards to Examine Chlorinated Solvent Behaviour

这项研究涉及合成有机污染物的研究，主要用作工业清洗溶剂，在浅（< 20米）深度的富含粘土的地质沉积物中，污染可能对地下水资源和地表环境构成威胁。通常情况下，污染是在几十年前进入地下的，当时这些化学物质的泄漏和溢出在加拿大及其他地区几乎所有的工业区都很常见。从那时起，化学物质在地下水中溶解和迁移，一些污染物通过扩散转移到非常低渗透率的区域，在那里它有可能造成异常长期的污染，并阻碍成功的补救。在这个研究项目中，化学物质的长期行为将通过在安大略省南部两个有代表性的地点（靠近萨尼亚和博登）进行的控制良好的现场实验进行调查。在这些地点，我和同事们在13-21年前开始了实地实验，深入研究在受控条件下释放或放置到2-12米深的地下的氯化溶剂的分布和行为。在这项拟议的研究中，我将回到这两个受污染的地点，应用新的、先进的实验室和现场方法来确定随着时间的推移发生的变化，以及哪些过程控制着污染物的扩散和衰减。重点将放在重要的过程上，包括扩散、降解和吸附。我们有理由认为，微生物造成的降解在过去十年中变得更加活跃，其速度缓慢但重要，只有在如此长的时间内才能量化。这项研究将改善预测这种常见类型的地下污染将持续存在并造成影响的时间尺度的前景，从而为有关场地修复的决策提供改进的基础。

This research concerns the study of synthetic organic contaminants, primarily used as industrial cleaning solvents, in clay-rich geological deposits at shallow (< 20 m) depth where the contamination can be a threat to both groundwater resources and the surface environment. Typically, the contamination entered the ground decades ago when leaks and spills of these chemicals were common in nearly all industrial regions of Canada and beyond. Since that time, the chemicals have dissolved and migrated in groundwater flow, and some of the contaminant mass has been transferred by diffusion into very low permeability zones where it has potential to cause exceptionally long-term contamination and impede successful remediation. In this research program, the long-term behaviour of the chemicals will be investigated using well- controlled field experiments in progress at two representative locations in the southern part of Ontario (near Sarnia and Borden). At these locations, colleagues and I initiated field experiments 13-21 years ago, intensely studying the distribution and behaviour of chlorinated solvents that were released or emplaced under controlled conditions, into the subsurface at depths of 2-12 m. In this proposed research, I will return to these two contaminated sites to apply new, advanced laboratory and field methodologies to determine the changes that have occurred over time and which processes govern the spread and attenuation of the contaminants. The emphasis will be on important processes including diffusion, degradation, and sorption. There is reason to expect that degradation caused by microbes has become more active over the past decade, at slow but important rates only quantifiable over such long time periods. This research will improve prospects for predicting the time scales over which this common type of subsurface contamination will persist and cause impacts, and thereby provide an improved basis for decisions about site remediation.