NAPL source zone characterization and remediation technology performance assessment: recent developments and applications of tracer techniques

Several innovative tracer techniques have been introduced during the past 5 years for enhanced characterization of the "source zones" at sites contami nated with non-aqueous phase liquid (NAPL) wastes. These tracer techniques allow for an in situ estimation of domain-averaged values and spatial patte rns for NAPL saturation (S-n), NAPL-water interfacial area (a(nw)), and bio -geochemical reactivity (k(s)) within the target test zone. The tracer test s can be used to evaluate the spatial patterns in these parameters, both be fore and after implementing some in situ technique for site cleanup, in ord er to evaluate the effectiveness of remediation achieved and the possible i mpacts of the cleanup technology on hydrodynamic and bio-geochemical proces ses. Here, we review the theoretical and experimental basis for these trace r methods, present selected examples of recent field-scale applications, an d examine their reliability. (C) 2000 Elsevier Science B.V. All rights rese rved.