Tracer techniques for site characterization and remediation technology performance assessment: recent developments and applications

Several innovative tracer techniques have been introduced for an in situ estimation of domain-averaged values and spatial patterns in the nonaqueous phase liquid (NAPL) saturation (S-n), the NAPL-water interfacial area (a(nw)), and the biogeochemical reactivity (k(s)) within the target test zone, both before and after implementing some in situ technique for site cleanup for evaluating the effectiveness of remediation achieved. Here, we review the theoretical basis for these tracer methods present selected examples of recent field applications, and briefly discuss the reliability of these tracer methods.