Speaker:  Linda Abriola

Affiliation:  Dean, School of Engineering and Professor of 
Civil and Environmental Engineering, Tufts University


Title: Characterization of Contaminant Source Zones:  Progress and Challenges


Abstract: Chlorinated solvent contamination of aquifers is a 
recalcitrant problem that has challenged environmental engineering 
professionals, regulators, and site managers for decades.  When 
solvents are released to the subsurface, they create a persistent 
contaminant source and, consequently, their presence poses a long 
term health risk to downstream receptors.   Although significant 
effort has been directed toward improving methods for recovering 
such dense nonaqueous phase liquids (DNAPLs), it is now generally 
accepted that no single technology will result in complete mass 
removal.   Thus, over the last five years, research efforts have 
shifted from developing technologies for mass removal to site 
characterization and quantification of the benefits and limitations 
of partial mass removal.  This presentation provides an overview 
of coupled modeling and experimental studies designed to explore 
the evolution of DNAPL source zones and their influence on 
contaminant plumes, remediation technology performance, and 
downstream contaminant mass flux.   Research reveals that natural 
variability in subsurface properties tends to create highly 
heterogeneous distributions of DNAPL mass and that local-scale 
DNAPL mass distribution (DNAPL architecture) can have a dramatic 
influence on source longevity and the potential effectiveness 
of remedial technologies.   Thus, results suggest that knowledge 
of DNAPL architecture is required for effective site management.   
Unfortunately, available technologies, appropriate for local-scale 
characterization, tend to be too invasive and costly for field 
deployment.  Furthermore, fine-scale simulation (prediction) of 
DNAPL architecture requires intense computational effort and 
unrealistically detailed knowledge of subsurface heterogeneity 
and DNAPL release conditions.  Alternative approaches for source 
zone characterization and ongoing research designed to address 
these challenges are described.