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

点击翻译按钮获取中文摘要

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.