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Hydrodynamic Forcing Mobilizes Cu in Low-Permeability Estuarine Sediments
Minwei Xie1,2, Ning Wang1,2, Jean-François Gaillard1
1Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3109, United States.
Environmental Science & Technology
|April 8, 2016
Summary
Hydrodynamics significantly impact metal efflux from low-permeability sediments, especially coarser ones. Sediment resuspension causes temporary metal release, highlighting the role of sediment properties and water flow in metal mobility.
Area of Science:
- Environmental Science
- Geochemistry
- Sedimentology
Background:
- Overlying hydrodynamics are known to influence surface-porewater exchanges in permeable sediments.
- These effects are less understood in low-permeability sediments, common in estuarine environments.
- Metal efflux from sediments is a critical process in contaminant fate and transport.
Purpose of the Study:
- To investigate the impact of varying hydrodynamic conditions on metal efflux from low-permeability estuarine sediments.
- To determine how sediment characteristics, such as particle size distribution, mediate hydrodynamic effects.
- To assess the role of episodic sediment resuspension in metal mobilization.
Main Methods:
- Laboratory experiments using controlled hydrodynamic shear in mesocosms.
- Analysis of copper (Cu) concentrations in overlying water and porewater.
- Comparison of two Cu-contaminated estuarine sediments with similar permeability but different particle sizes.
- Inclusion of episodic sediment resuspension events.
Main Results:
- Hydrodynamic forcing enhanced Cu mobilization and efflux from coarser-grained sediments, but not finer-grained ones.
- Episodic sediment resuspension led to transient increases in water column Cu concentrations.
- Particulate metal concentrations spiked during resuspension but returned to baseline levels post-disturbance.
- Sediment heterogeneity played a key role in mediating hydrodynamic impacts.
Conclusions:
- Overlying hydrodynamics can influence metal mobility and efflux even in low-permeability sediments.
- Sediment properties, particularly particle size distribution, are critical factors in determining the extent of hydrodynamic influence.
- Sediment resuspension events cause temporary metal release, with recovery dependent on sediment characteristics.
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