Ground Water Contamination Arising from Dense Brines: Integrating Theory, Laboratory Experiments and Field Observations

There are numerous instances where aqueous wastes denser than water (brines) were released to the subsurface from landfill leachates, perchlorate spills, and other industrial wastes.  The density contrast between the waste and ambient groundwater can emplace the waste liquid and associated contaminants in less accessible regions of the aquifer and limit release into the flowing groundwater.  For contaminants such as perchlorate and chromate that can be present in wastes at concentrations orders of magnitude greater than acceptable levels, emplaced brines represent long-term sources of contamination.    This talk will summarize some simple models for brine migration, use theory to generalize experimental measurements that define when dense brines will present problems in the subsurface, and then illustrate the long term consequences of emplaced brines suggested from selected field sites.  As with all subsurface contaminants, source terms must be identified and mitigated to minimize the time required for remediation. For perchlorate, chromate and a number of other contaminants released as dense brines, a persistent source of groundwater contamination should be anticipated.