Grantee Research Project Results
Final Report: Contaminant Transport Across Cohesive Sediment Interfaces.
EPA Grant Number: R825513C002Subproject: this is subproject number 002 , established and managed by the Center Director under grant R825513
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: The Southeastern Center for Air Pollution and Epidemiology: Multiscale Measurements and Modeling of Mixtures
Center Director: Tolbert, Paige
Title: Contaminant Transport Across Cohesive Sediment Interfaces.
Investigators: Amirtharajah, A. , Sturm, T. W.
Institution: Georgia Institute of Technology
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1992 through January 1, 1995
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text | Recipients Lists
Research Category: Hazardous Substance Research Centers , Land and Waste Management
Objective:
The objectives of this research were 1) to measure resuspension/detachment rates of clay particles and adsorbed contaminants in flume and column studies, and 2) to relate the detachment or resuspension rates to imposed bed shear stress as well as microscopic, interparticle forces as affected by humic substances, pH and ionic strength, ans sediment type. The ultimate goal of this effort was to improve numerical models used to predict resuspension and subsequent transport of contaminated, cohesive sediments in natural water bodies due to storm events or dredging activities.
Summary/Accomplishments (Outputs/Outcomes):
Flume studies were conducted under conditions of uniform flow in a recirculating tilting flume which was constructed for the purposes of this project. Experiments were performed at bed slopes of 0.002 and 0.003. The bed shear stress was varied from 1.0 to 2.4 N/m2 by changing the flume discharge and bed slope. Flow depths varied from 4.2 to 9.1 cm. And mean velocities ranged between 0.33 and 0.54 m/s. Bed shear stresses were determined from the uniform flow formula after correlation with shear stresses calculated from detailed velocity profiles measured near the bed at the test section.
The resuspension characteristics of kaolinite clay and bottom sediment collected from the Calcasieu River near a contaminated industrial site in Lake Charles, Louisiana were studied in the flume. The rate of erosion and the total mass of sediment eroded were monitored as a function of shear stress. In addition, the characteristics of the kaolinite samples were varied by changing the pH of the sediment pore water in the range from 3 to 8, and by adsorbing various amounts of natural organic matter (NOM) from the Suwanee River.
During an erosion event, a sample stream was taken continuously downstream of the flume test section and was passed through a Chemtrac Particle Monitor which was calibrated to determine particle concentration from which initial erosion rates were determined.
Column experiments were conducted in a glass column of 27 mm diameter which was packed with 175 g of fine glass beads. The column experiments were conducted in two steps: an attachment step followed by a detachment step. During filtration all effluent was collected for later measurements. After attachment, the column was backwashed under fluidized conditions with a 20% bed expansion. All backwash water was collected for subsequent mass measurements. The percent detachment as mass was then determined by mass balances as a function of ionic strength and pH, and concentration of adsorbed NOM on the kaolinite particles.
Interparticle forces were calculated to determine the net attractive or repulsive forces between particles as a function of separation distance, pH, and ionic strength. DLVO forces due to the electrical double-layer and van der Waals attractive interactions as well as non-DLVO forces due to Born repulsion and hydration effects were calculated. These calculations and the variation of interparticle forces with pH and inoic strength were validated with detachment experiments using spherical particles in a well defined experimental setup. Then, natural kaolinite particles were modeled as small hexagonal platelets. Cleavage surfaces of the kaolinite particles were represented by a flat plate while interactions of platelet edges were represented by a cylinder. These force calculations have not been done previously and were developed as part of this research.
In addition to the well known influence of bed shear stress on erosion or resuspension, the results of this research have demonstrated the important influence that pH, organic matter, and clay mineralogy have on rates of detachment and erosion of cohesive sediments in both column and flume experiments. Relationships were developed for quantifying the effect of concentration of adsorbed organic matter, sediment pore water pH, and bed shear stress on erosion rates. This represents the first time that the role of natural organic matter in bottom sediments has been quantified with respect to the erosion/resuspension process. In addition, microscopic force calculations that were developed for the first time in this research show how to predict particle-particle interactions in cohesive sediments and then to explain erosion behavior based on those interactions.
The flume experiments showed that initial erosion rates increased linearly with nondimensional excess shear stress. The parameter values of critical shear stress c and erosion rate coefficient M were found to depend directly on sediment pore water pH and adsorbed organic mater. At an intermediate pH range of 5 to 7 , the kaolinite was shown to be much more susceptible to erosion in comparison to low or high values of pH. Similar effects of attachment pH on percent detachment were observed in the column experiments. In the flume experiments, increasing concentrations of adsorbed natural organic matter on the kaolinite particles in ranges expected in natural environments caused increased erosion rates, which is especially significant because of the increased likelihood of contaminants being associated with sediments high in organic matter. At very high concentrations of organic matter, the column experiments displayed a decrease in percent detachment during backwash with 20% bed expansion possibly due to polymeric bridging. These results suggest that pH and ionic strength versus organic matter and divalent cations have conflicting and complex effects on the interparticle microscopic forces and the corresponding erosion of cohesive sediments. These parameters are the most important factors to consider when microorganism-mediated transformation in organics and pH occur in bottom sediments of rivers. They are also important factors to consider in the dredging of bottom sediments which have a significant accumulation of organic matter.
The results of the research have further demonstrated the significant impact that types of particle-particle interactions in cohesive sediments can have on their rates of erosion. Theoretical calculations of interparticle forces have successfully predicted the types of particle interactions to be expected under given conditions of pH and organic matter and hence can be used to explain the experimental erosion and detachment behavior observed in cohesive sediments. Of even more significance for future research is that the microscopic force calculations provide a theoretical basis for predication critical shear stresses and hence ultimately, erosion relationships.
It is recommended that because of the significant influence of organic matter on erosion relationships and the very limited information available in the published literature, further study should examine the effects of the amounts of adsorbed natural organic matter on erosion of clay particles in terms or the changes caused in repulsive electrostatic interactions contrasted with flocculation due to bridging effects. A major focus of these studies should be on the erosion of kaolinite with natural organic matter complexed with heavy metal contaminants. In addition, studies on the effect of organic matter on mobilization of metal contaminants after sediment resuspension and exposure to the water column have occurred are needed to determine the ultimate fate of the contaminant itself in addition to the sediment. Finally, extension of the microscopic force approach to sediments other than kaolinite would greatly broaden its applicability for the determination of erosion/resuspension relationships of a more general nature.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other subproject views: | All 19 publications | 5 publications in selected types | All 4 journal articles |
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Other center views: | All 392 publications | 154 publications in selected types | All 106 journal articles |
Type | Citation | ||
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Amirtharajah A, Raveendran P. Detachment of colloids from sediments and sand grains. Colloids and Surfaces A - Physicochemical and Engineering Aspects 1993;73:211-227. |
R825513C002 (Final) |
not available |
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Raveendran P, Amirtharajah A. Role of short range forces in particle detachment during filter backwashing. Journal of Environmental Engineering, ASCE 1995;121(12):860-868. |
R825513C002 (Final) |
not available |
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Raveendran P, Amirtharajah A. Mechanisms of particle detachment during filtration and backwashing. Fluid/Particle Separation Journal 1992;5(2):1-4. |
R825513C002 (Final) |
not available |
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Sturm TW. How river sediments erode and resuspend. Centerpoint 1997;4(1). |
R825513C002 (Final) |
not available |
Supplemental Keywords:
interparticle forces, dredging, and storm events., RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Chemical Engineering, Contaminated Sediments, Environmental Chemistry, Fate & Transport, Analytical Chemistry, Hazardous Waste, Ecology and Ecosystems, Hazardous, Environmental Engineering, environmental technology, sediment treatment, hazardous waste management, hazardous waste treatment, risk assessment, fate and transport, contaminated marine sediment, soil and groundwater remediation, biodegradation, contaminated sediment, kinetics, chemical contaminants, contaminated soil, bioremediation of soils, marine sediments, remediation, chemical kinetics, hydrology, biotransformation, flume studies, currents, anaerobic biotransformation, extraction of metals, Lake Charles, technology transfer, heavy metals, bioremediation, CERCLA, aquifer fate and treatment, technical outreachProgress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R825513 The Southeastern Center for Air Pollution and Epidemiology: Multiscale Measurements and Modeling of Mixtures Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825513C001 Sediment Resuspension and Contaminant Transport in an Estuary.
R825513C002 Contaminant Transport Across Cohesive Sediment Interfaces.
R825513C003 Mobilization and Fate of Inorganic Contaminant due to Resuspension of Cohesive Sediment.
R825513C004 Source Identification, Transformation, and Transport Processes of N-, O- and S- Containing Organic Chemicals in Wetland and Upland Sediments.
R825513C005 Mobility and Transport of Radium from Sediment and Waste Pits.
R825513C006 Anaerobic Biodegradation of 2,4,6-Trinitrotoluene and Other Nitroaromatic Compounds by Clostridium Acetobutylicum.
R825513C007 Investigation on the Fate and Biotransformation of Hexachlorobutadiene and Chlorobenzenes in a Sediment-Water Estuarine System
R825513C008 An Investigation of Chemical Transport from Contaminated Sediments through Porous Containment Structures
R825513C009 Evaluation of Placement and Effectiveness of Sediment Caps
R825513C010 Coupled Biological and Physicochemical Bed-Sediment Processes
R825513C011 Pollutant Fluxes to Aquatic Systems via Coupled Biological and Physicochemical Bed-Sediment Processes
R825513C012 Controls on Metals Partitioning in Contaminated Sediments
R825513C013 Phytoremediation of TNT Contaminated Soil and Groundwaters
R825513C014 Sediment-Based Remediation of Hazardous Substances at a Contaminated Military Base
R825513C015 Effect of Natural Dynamic Changes on Pollutant-Sediment Interaction
R825513C016 Desorption of Nonpolar Organic Pollutants from Historically Contaminated Sediments and Dredged Materials
R825513C017 Modeling Air Emissions of Organic Compounds from Contaminated Sediments and Dredged Materials title change in last year to "Long-term Release of Pollutants from Contaminated Sediment Dredged Material"
R825513C018 Development of an Integrated Optic Interferometer for In-Situ Monitoring of Volatile Hydrocarbons
R825513C019 Bioremediation of Contaminated Sediments and Dredged Material
R825513C020 Bioremediation of Sediments Contaminated with Polyaromatic Hydrocarbons
R825513C021 Role of Particles in Mobilizing Hazardous Chemicals in Urban Runoff
R825513C022 Particle Transport and Deposit Morphology at the Sediment/Water Interface
R825513C023 Uptake of Metal Ions from Aqueous Solutions by Sediments
R825513C024 Bioavailability of Desorption Resistant Hydrocarbons in Sediment-Water Systems.
R825513C025 Interactive Roles of Microbial and Spartina Populations in Mercury Methylation Processes in Bioremediation of Contaminated Sediments in Salt-Marsh Systems
R825513C026 Evaluation of Physical-Chemical Methods for Rapid Assessment of the Bioavailability of Moderately Polar Compounds in Sediments
R825513C027 Freshwater Bioturbators in Riverine Sediments as Enhancers of Contaminant Release
R825513C028 Characterization of Laguna Madre Contaminated Sediments.
R825513C029 The Role of Competitive Adsorption of Suspended Sediments in Determining Partitioning and Colloidal Stability.
R825513C030 Remediation of TNT-Contaminated Soil by Cyanobacterial Mat.
R825513C031 Experimental and Detailed Mathematical Modeling of Diffusion of Contaminants in Fluids
R825513C033 Application of Biotechnology in Bioremediation of Contaminated Sediments
R825513C034 Characterization of PAH's Degrading Bacteria in Coastal Sediments
R825513C035 Dynamic Aspects of Metal Speciation in the Miami River Sediments in Relation to Particle Size Distribution of Chemical Heterogeneity
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
4 journal articles for this subproject
Main Center: R825513
392 publications for this center
106 journal articles for this center