Relationship between dual-domain parameters and practical characterization data

Area of Science:

• Environmental Science
• Hydrogeology
• Geochemistry

Background:

• Single-domain (advection-dispersion) models show limitations in predicting solute transport.
• Dual-domain models offer improved agreement with observational data in a posteriori fitting.
• Predictive application of dual-domain models at field scales is hindered by limited characterization of permeability and flow.

Purpose of the Study:

• Investigate the variation of single-rate mass transfer parameters in dual-domain solute transport models.
• Understand the influence of aquifer attributes and contaminant exposure on these parameters.
• Develop empirical relationships for dual-domain transport parameters based on aquifer characteristics.

Main Methods:

• Conducted high-resolution numerical simulations across 30 scenarios with varying aquifer properties and flow fields.
• Empirically determined optimal dual-domain transport parameters by matching breakthrough curves.
• Analyzed the impact of permeability distribution, flow, mass transfer timescale, and exposure time on model parameters.

Main Results:

• Mobile porosity is influenced by permeability contrast, spatial correlation length, high-permeability zone connectivity, and flow direction.
• Non-participating porosity is crucial for empirical fitting and depends on flow alignment, diffusion, and spatial correlation.
• The Damkohler number (non-dimensional mass transfer coefficient) approaches 1.0 and decreases with exposure time.
• Macrodispersion combined with first-order mass transfer yields the best empirical fit.

Conclusions:

• Dual-domain model parameterization is sensitive to aquifer heterogeneity and flow conditions.
• Predicting dual-domain parameters from measurable aquifer attributes shows limited success.
• Further research is needed to refine predictive capabilities of dual-domain models for field-scale contaminant transport.