This seminar is the first in a series sponsored by the NIEHS Superfund Basic Research Program. The presence of source zones containing dense non-aqueous phase liquid (DNAPL) is usually the single most important factor limiting the characterization and cleanup of organic-contaminated sites. Unfortunately, because of the complexities associated with the distribution and mass transfer of DNAPLs, as well as the heterogeneity of subsurface environments, it is generally not possible to remove all DNAPL mass from the source zone. Thus, the issue for many sites becomes the relative costs/benefits of source reduction, including the impact on mass flux. To address the source-reduction issue and mass flux measurements, as well as to accurately assess the human-health risks associated with chlorinated solvents and other DNAPLs in the subsurface, it is essential to gain a better understanding of the distribution and mass-transfer behavior of DNAPLs in subsurface systems. Additional SBRP seminars in September and October will address DNAPLs monitoring, biological remediation, and chemical/physical remediation methods. |