Dissolution of a multicomponent DNAPL pool in an experimental aquifer

Area of Science:

• Environmental Science
• Hydrogeology
• Geochemistry

Background:

• Dense nonaqueous phase liquid (DNAPL) pools are persistent sources of groundwater contamination.
• Understanding the dissolution and transport of multicomponent DNAPLs is crucial for effective remediation strategies.

Purpose of the Study:

• To investigate the dissolution behavior and plume dynamics of a binary DNAPL mixture (tetrachloroethylene and 1,1,2-trichloroethane).
• To compare the spatial-temporal plume patterns of major versus minor DNAPL components.
• To evaluate the effectiveness of a semi-analytical model in simulating multicomponent DNAPL dissolution.

Main Methods:

• Conducted a bench-scale, three-dimensional aquifer model experiment with a circular DNAPL pool.
• The DNAPL pool consisted of tetrachloroethylene (PCE) as the major component and 1,1,2-trichloroethane (1,1,2-TCA) as the minor component.
• Monitored downgradient contaminant concentrations over time at multiple locations.

Main Results:

• Observed distinct plume behaviors for the major (PCE) and minor (1,1,2-TCA) components.
• A stable plume pattern was observed for PCE, while 1,1,2-TCA concentrations varied over time.
• The semi-analytical model successfully replicated the observed plume structures and dynamics for both components.

Conclusions:

• The composition of DNAPL pools significantly influences the resulting contaminant plume characteristics.
• Differential dissolution rates lead to distinct spatial-temporal plume development for multicomponent DNAPLs.
• Semi-analytical modeling provides a valuable tool for predicting contaminant transport from complex DNAPL sources.