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09:49
Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation
Published on: November 18, 2015
Diffusive flux and pore anisotropy in sedimentary rocks
C E Schaefer1, R M Towne, V Lazouskaya
1Shaw Environmental, Inc., Lawrenceville, NJ 08648, United States. charles.schaefer@shawgrp.com
Journal of Contaminant Hydrology
|February 14, 2012
Summary
Bedding orientation significantly impacts contaminant diffusion in bedrock. New models incorporating apparent porosity improve predictions for anisotropic rocks, crucial for understanding contaminant plume behavior.
Area of Science:
- Geochemistry
- Hydrogeology
- Environmental Science
Background:
- Dissolved contaminant diffusion in bedrock influences contaminant plume extent and longevity.
- Bedding orientation in layered rocks is a key factor affecting diffusion rates.
Purpose of the Study:
- To quantify diffusive flux parallel and normal to mineral bedding in anisotropic sedimentary rocks.
- To evaluate existing models and develop an improved model for predicting effective diffusion coefficients.
Main Methods:
- Laboratory experiments on minimally disturbed bedrock cores.
- Measurement of effective diffusion coefficients.
- Scanning electron microscopy to determine apparent porosity.
Main Results:
- Effective diffusion coefficients varied from 4.9×10(-8) to 6.5×10(-7)cm(2)/s.
- Diffusion coefficients differed up to 10-fold between orientations parallel and normal to bedding.
- Apparent porosity differences correlated with diffusion coefficient variations.
Conclusions:
- Existing empirical models inaccurately predict diffusion coefficients in anisotropic rocks.
- A modified model based on apparent porosity offers reasonable predictions for experimental diffusion data.
- Accurate modeling of diffusion is vital for managing contaminant plumes in sedimentary rock formations.
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