NMR IMAGING OF NONAQUEOUS-PHASE LIQUID DISSOLUTION IN A POROUS-MEDIUM

It is demonstrated how NMR imaging can be used noninvasively to quanti fy the volume of nonaqueous phase liquid (NAPL) present in an otherwis e water-saturated porous medium. Data were recorded during the operati on of a pump and treat (PT) remediation scheme on a bed of water-satur ated sand contained within a vertical column. The model contaminant us ed was n-hexanol, and three different aqueous flow rates were employed . These data were then critically compared with the predictions of thr ee models currently used to describe the dissolution of NAPL during a PT scheme: the linear mass-transfer model, the pore-diffusion model, a nd the shrinking-core model. The pore-diffusion model gave best agreem ent with the experimental data. However, none of the models predicted the observed dependence of mass transfer on Darcy velocity.