Hydraulic/partitioning tracer tomography for DNAPL source zone characterization: small-scale sandbox experiments.

Area of Science:

• Environmental Science
• Geoscience
• Chemical Engineering

Background:

• Dense nonaqueous phase liquids (DNAPLs) are persistent groundwater contaminants due to complex subsurface distributions.
• Site remediation is challenging, leading to contamination lasting decades to centuries.

Purpose of the Study:

• To demonstrate the efficacy of the Sequential Successive Linear Estimator (SSLE) algorithm for imaging DNAPL source zones.
• To improve the understanding of DNAPL saturation and hydraulic heterogeneity for effective remediation.

Main Methods:

• Fusion of hydraulic and partitioning tracer tomography (HPTT) data.
• Application of the SSLE algorithm to estimate DNAPL saturation (S(N)) and hydraulic conductivity (K) heterogeneity.
• Laboratory experiments using sandbox models.

Main Results:

• The SSLE algorithm successfully images DNAPL saturation distributions, showing favorable comparison with visual observations in sandbox experiments.
• Local saturation estimates from core samples were less accurate than SSLE-derived distributions.
• Accurate delineation of hydraulic heterogeneity significantly impacts computed S(N) distributions.

Conclusions:

• The SSLE algorithm, utilizing HPTT, provides a nondestructive and repeatable method for characterizing DNAPL source zones.
• Accurate characterization of subsurface hydraulic properties is crucial for reliable DNAPL remediation strategies.