Colloid Deposit Morphology Controls Permeability in Porous Media

The Science

Processes occurring in soils and aquifers play a crucial role in contaminant remediation and carbon cycling. The flow of water through porous media like soils and aquifers, which is essential for contaminant remediation and carbon cycling, depends on the permeability, which determines how much water flows for a given hydraulic driving force. It is widely recognized that colloids (fine particles including soils, chemical precipitates, and bacteria) often control permeability, and it is known that colloid deposit morphology (the structure of deposited colloids) is a fundamental aspect of permeability, but until recently no experimental techniques were available to measure colloid deposit morphology within porous media.

The Impact

Processes occurring in soils and aquifers play a crucial role in contaminant remediation and carbon cycling. The flow of water through porous media like soils and aquifers, which is essential for contaminant remediation and carbon cycling, depends on the permeability, which determines how much water flows for a given hydraulic driving force. It is widely recognized that colloids (fine particles including soils, chemical precipitates, and bacteria) often control permeability, and it is known that colloid deposit morphology (the structure of deposited colloids) is a fundamental aspect of permeability, but until recently no experimental techniques were available to measure colloid deposit morphology within porous media.

Summary

These observations suggest a deposition scenario in which large and uniform aggregates become deposits, which reduce porosity, lead to higher fluid shear forces, which then decompose the deposits, filling the pore space with small and dendritic fragments of aggregate. Accordingly, for the first time, observations are available to quantify the relationship between the macroscopic variables of ionic strength and water velocity and the pore-scale variables of colloid deposit morphology, which can be conceptualized as an emergent property of the system. This work paves the way for future studies that will quantify the complex feedback process between flow, chemistry, and biology in soils and aquifers.

Principal Investigator

Eric Roth
University of Colorado Boulder
[email protected]

Program Manager

Paul Bayer
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This research was supported by the Subsurface Biogeochemistry Research Program (SBR; award DE-SC0006962) of the Office of Biological and Environmental Research (BER), within the U.S. Department of Energy (DOE) Office of Science. B.G. was supported as part of the Subsurface Science Scientific Focus Area funded by BER within the DOE Office of Science (award DE-AC02-05CH11231).

References