T5 PM Emerging Pollutants
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 321-323

(HUN-1118-444495) Brines as an Emerging Contaminant Transport Mechanism in the Subsurface.

Hunt, J¹, ¹ University of California, Berkeley, CA, USA

ABSTRACT- Concentrated salt solutions can become source terms for a number of environmental contaminants released into subsurface. These brines arise from industrial processes such as solid rocket fuel production, landfill leachates, and nuclear fuel reprocessing. In addition, dense and viscous fluids such as lactate and hydrogen peroxide are being introduced into the subsurface for remediation purposes without fully appreciating transport pathways. Brine transport processes are quantified from the considerable literature available combined with recent experimental data that quantify the importance of density and viscosity contrasts. Since brines tend to sink to less accessible locations in the subsurface, contaminant release from brine pools will be mass transfer limited. For contaminants soluble in water but with very low acceptable concentrations such as radioactive wastes, chromate, and perchlorate, models predict that groundwater quality will be degraded for decades. Two examples from field sites illustrate the possible importance of brines as source terms. One site is where cooling water containing chromate was discharged over 40 years ago, but chromate still continues to contaminant an aquifer. Another field site examines a persistent perchlorate plume decades after the releases. For conventional and non-conventional pollutants present within dense brines, source recognition and control remain illusive goals.

Key words: chromate, perchlorate, density, viscosity