HR: 10:35h
AN: H42A-02    [Abstracts]
TI: Brines as Sources of Long-term Subsurface Contamination
AU: * Flowers, T C
EM: tflowers@exponent.com
AF: Exponent* Failure Analysis Associates, 149 Commonwealth Drive, Menlo Park, CA 94025 United States
AU: Hunt, J R
EM: hunt@ce.berkeley.edu
AF: University of California, Civil and Environmental Engineering, Berkeley, CA 94720-1710 United States
AB: Concentrated salt solutions, i.e. brines, are source terms for environmental contaminants released into surface waters and groundwaters. Brines arise from both natural and industrial processes such as natural salt deposits, solid rocket fuel production, landfill leachates, nuclear fuel reprocessing, and acid rock drainage. Additionally, many of the in-situ remediation fluids that have been implemented at the pilot or the field scale are also classified as brines. While brines are miscible with water, mixing processes are slow in the subsurface and this constrains the dilution of contaminants present within brines and the delivery of remediation fluids to sites where reactions are needed. The mixing of brines during their vertical migration through aquifers is determined by aquifer permeability as well as differences in density and viscosity between the brine and the ambient groundwater. The stability criterion for brine displacement was predicted in 1952 by Hill and the resulting dispersion at the mixing front is quantified by a compilation of literature data and the acquisition of new experimental data. As brines sink through aquifers, they become emplaced in less accessible locations where mass transfer models predict that contaminants within brines are slowly released into flowing groundwater. For radioactive wastes and environmental contaminants with very low acceptable concentrations, groundwater quality can be impacted for decades. Field data from a cooling water disposal site suggest that a dense brine is likely still present as a source term 40 years after waste disposal was stopped. Overall, analysis of pollution sources, quantification of transport processes, generalization of laboratory data, and limited evaluation of field data indicate that brines represent long-term sources of groundwater contamination and that source control has not been seriously addressed.
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting