Equilibrium nonaqueous phase liquid pool geometry in coarse soils with discrete textural interfaces

Area of Science:

• Environmental Science
• Geology
• Hydrogeology

Background:

• Understanding the geometry of nonaqueous phase liquid (NAPL) pools and mounds is critical for environmental remediation.
• Existing models often simplify soil complexities and fluid behavior, leading to potential inaccuracies in predicting contaminant distribution.

Purpose of the Study:

• To develop a comprehensive model for NAPL pool and mound geometry in homogeneous and heterogeneous soils.
• To integrate the effects of capillary pressure-saturation curve hysteresis and entry pressures into NAPL geometry conceptualization.

Main Methods:

• Development of a conceptual model incorporating capillary pressure hysteresis and entry pressures.
• Analysis of light NAPL (LNAPL) and dense NAPL (DNAPL) behavior in homogeneous soils and soils with textural interfaces.
• Validation of the model through comparison with experimental data on pool thicknesses and LNAPL lens location.

Main Results:

• Capillary pressure hysteresis is essential for the existence of LNAPL pools in homogeneous soils.
• DNAPL mounding on horizontal textural interfaces requires lateral confining boundaries if hysteresis is not considered.
• The proposed model predicts remobilization of DNAPL pools at lower hydraulic gradients than previously estimated.

Conclusions:

• The model accurately predicts LNAPL and DNAPL pool geometries and LNAPL lens positioning relative to the capillary fringe.
• Incorporating hysteresis significantly improves the conceptualization of NAPL behavior in subsurface environments.
• This refined understanding is vital for effective site characterization and remediation strategies for NAPL-contaminated sites.