Field scale DNAPLs transport under nonequilibrium sorption conditions.
The purpose of this work is to study the desorption of dense nonaqueous phase liquids (DNAPLs), TCE in particular, from solid particles in field scale heterogeneous aquifers upon their remediation. A computer program, capable of simulating the fate and transport of NAPLs in porous media, has been developed to work under nonequilibrium sorption conditions. The model has been applied to a field scale site at Hill Air Force Base, Utah, which has been contaminated by DNAPLs. The simulated domain was 155 ft (47.25 m) long, 60 ft (18.29 m) wide, and 15.5 ft (4.72 m) thick. This thickness represents only the saturated zone of the aquifer. Changes in permeability, grain size distribution, and sorptive properties throughout the site have been incorporated into the model. Immediately after the aquifer cleanup, the DNAPL concentration in the aqueous phase was assumed to be zero, and this was considered the start-off time for the simulation. Results show that, with an increase in time, the TCE diffused out of the solid particles, forming a plume. The rate of contaminant diffusion was observed to be very fast at the start, followed by a very slow stage, with a number of years required for substantial desorption of the contaminant from the solid particles. There were local variations in contaminant concentration in the fluid phase across the site due to aquifer heterogeneity. A comparison between numerical results and water samples taken from the site after the end of the cleanup operation is also presented.
School of Mechanical, Aerospace, and Civil Engineering, The University of Manchester, Manchester, M60 1QD, United Kingdom.
Ashraf A
AA
Ahmed
Daoyi
D
Chen
D000327:Adsorption; D007220:Industrial Waste; D007700:Kinetics; D010316:Particle Size; D010539:Permeability; D016062:Porosity; D012987:Soil / Q000032:analysis*; D014241:Trichloroethylene / Q000032:analysis* / Q000737:chemistry; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
D007220:Industrial Waste; D012987:Soil; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene