Grantee Research Project Results
Final Report: Contaminated Sediments
EPA Grant Number: R825278Title: Contaminated Sediments
Investigators: Lick, Wilbert
Institution: University of California - Santa Barbara
EPA Project Officer: Aja, Hayley
Project Period: October 1, 1996 through September 30, 1999 (Extended to September 30, 2000)
Project Amount: $659,764
RFA: Risk-Based Decisions for Contaminated Sediments (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
As stated in our proposal, the general purpose of our research was to understand and predict the transport and fate of sediments and hydrophobic organic chemicals (HOCs) in aquatic systems. Specific emphases were: (1) the transport and fate of HOCs due to resuspension of bottom sediments, especially during severe events, and the biological, chemical, and physical factors controlling this resuspension, and (2) the biogeochemical partitioning of HOCs between sediments, water, and biota in order to better predict the bioavailability of contaminants and the subsequent interactions between contaminants and biota. In our research, the transport, fate, and effects of mixtures of HOCs as well as single chemicals was investigated.Specific objectives were as follows:
1. Quantitatively determine the erosion rates and the parameters on which erosion rates depend for both reconstructed sediments and undisturbed field sediments at high shear stresses (up to 10 N/m2) and as a function of depth (up to 1 m). As part of this, critical shear stresses for erosion as a function of depth were also measured. Sediment cores were prepared so that the effects of the following parameters on the erosion rates could be determined: amount and manner of sediment deposition, average particle size and particle size distribution, mineralogy, size and number of gas bubbles and gas pockets, amounts of organic matter, and the presence and activity of benthic organisms. Erosion rates of sediments deposited during flows of different magnitude will also be determined. Undisturbed field cores were analyzed and compared with results from laboratory cores in order to relate erosion rates to bulk properties for in situ sediments.
2. Measure deposition rates of suspended sediments as a function of flow rate (shear stress) and suspended sediment concentration with particle/floc sizes and densities of the suspended sediments and surficial bulk properties of the bottom sediments as parameters.
3. Determine the adsorption rates, desorption rates, and partitioning of HOCs and mixtures of HOCs sorbing to suspended sediments and bottom sediments. This included a study of the flocculation and sorption dynamics of colloids in different waters, such as lake waters, sea waters, and tap waters.
4. Determine the availability of HOCs and mixtures of HOCs to bacteria as a function of time with the total contaminant concentration in the bottom sediments as well as the contaminant concentrations in each of the water, colloid, and solid compartments as parameters.
5. Develop a truly predictive model of sediment transport and fate and contaminant transport, bioavailability, and effects on biota in aquatic systems, especially as affected by severe events. This was done as an extension of our presently existing hydrodynamic, sediment, and contaminant transport and fate models. The modeling emphasized sediment erosion and deposition, the flocculation of fine-grained sediments and colloids, the time-dependent sorption and partitioning of HOCs in suspended and bottom sediments, the sediment-water fluxes of HOCs as affected by slow sorption rates, and the time-dependent availability of HOCs to bacteria and macroscopic benthic organisms. Parameters needed in the models were determined on the basis of our laboratory experiments.
Summary/Accomplishments (Outputs/Outcomes):
Substantial work on all five of these objectives has been accomplished. Progress on the project through December 2000 is as follows. Titles of all referenced and published articles are listed below.
1. The determination of erosion rates and the parameters on which these rates depend. A unique flume, called Sedflume, was previously designed, developed, and tested. Sediment erosion rates as a function of shear stress and with depth in the sediments were then determined for relatively undisturbed sediments from several rivers and lakes. Field and laboratory experiments demonstrated that erosion rates depended on at least the following parameters: bulk density (or water content) of the sediments, particle size distribution as well as mean particle size, mineralogy, organic content, amounts and sizes of gas bubbles, oxidation and other chemical reactions, and time. Experiments have been conducted to isolate the effects of each of these parameters.
The first set of experiments was concerned with the effects of bulk density. The results of these experiments have been published (Jepsen, et al., 1997). A second set of experiments considered the effects of particle size and bulk density on the erosion of quartz particles (Roberts, et al., 1998). Experiments have also been done to investigate the effects of different minerals, with the emphasis on smectites as well as other clays. Bentonite has been shown to have a major stabilizing effect on sediments (Lijun, et al., 2001). Effects of minerals are being investigated further. Effects of gas on erosion rates in the Grand River have been investigated and reported (Jepsen, et al., 1999). An article summarizing the effects of sediment bulk properties on erosion rates has been published (Lick and McNeil, 2000). Approximate equations for a uniformly valid description of erosion rates as a function of the parameters listed above are presently being developed.
In addition to this laboratory work, Sedflume has been used to measure erosion rates of sediments in Long Beach Harbor and New York Harbor. This work has been supported by the U.S. Army Corps of Engineers. Our laboratory work has been used in the analyses of these field cores.
2. Deposition rates. Preliminary studies of deposition rates of suspended sediments have been made. Extensive studies of this process have been initiated.
3. Adsorption, desorption, and partitioning of hydrophobic organic chemicals to sediments. Extensive studies of the adsorption, desorption, and partitioning of several different HOCs (hexachlorobenzene and four different PCB congeners) have been made (Lick and Rapaka, 1996; Jepsen and Lick, 1996; Borglin, et al., 1996). This work has now been extended to include nonlinear isotherms and interactive effects in mixtures of HOCs (Jepsen and Lick, 1999).
In addition to sorption processes, the transport of chemicals in sediments, especially as affected by sorption processes, was investigated. The first set of experiments was concerned with the diffusion of tritiated water vapor (Deane, et al., 1998). A second set of experiments has now been done with HOCs diffusing in bottom sediments (Deane et al., 1999).
4. Bioavailability of HOCs. Laboratory experiments on the sorption of HOCs to bacteria are presently being done. When sediments are present, it is necessary to separate bacteria and sediments or, more generally, to measure the masses of sediments and bacteria independently. This is presently being investigated by using the uptake of radiolabeled chemicals (35S and 14C) by bacteria as a measure of bacterial activity and hence separately measure the masses of bacteria and sediments. Experiments are being done on the sorption of HOCs to bacteria in different stages (active, inactive, dead, and lysed). Significant differences between the different stages are being found. HOCs being used are hexachlorobenzene, several PCBs, and PCP.
5. Develop a predictive model of sediment and contaminant transport and fate. From the investigations described above, we have learned considerable about the significant processes which affect the transport and fate of chemicals, especially HOCs. As this occurs, this knowledge is incorporated into general transport and fate models. Overviews of this modeling have been reported (Ziegler and Lick, 1997). The modeling of HOCs in surface waters including finite reaction rates has now been done (Chroneer, et al., 1997). An improved sediment transport model, which now includes data from Sedflume, has also been developed with preliminary verification (Lick et al., 1998). More recent developments included in the sediment transport model are bed coarsening, several size components, and changes in bed properties with time (Jones and Lick, 2000).
Applications of this work are presently being made. Determination of erosion rates and the parameters on which they depend have been made by means of Sedflume for several different rivers. This work has been funded by several different agencies. Applications of this work are presently being made to the determination of sediment and contaminant transport and fate in the Maumee River. This work is being funded by EPA GLNPO.
Journal Articles on this Report : 10 Displayed | Download in RIS Format
Other project views: | All 17 publications | 16 publications in selected types | All 10 journal articles |
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Type | Citation | ||
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Lick W, Rapaka V. A quantitative analysis of the dynamics of the sorption of hydrophobic organic chemicals to suspended sediments. Environmental Toxicology and Chemistry 1996;15(7):1038-1048. |
R825278 (Final) |
not available |
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Jepsen R, Lick W. Parameters affecting the adsorption of PCBs to suspended sediments from the Detroit River. Journal of Great Lakes Research 1996;22(2):341-353. |
R825278 (Final) |
not available |
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Borglin S, Wilke A, Jepsen R, Lick W. Parameters affecting the desorption of hydrophobic organic chemicals from suspended sediments. Environmental Toxicology and Chemistry 1996;15(12):2254-2262. |
R825278 (Final) |
not available |
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Jepsen R, Roberts J, Lick W. Effects of bulk density on sediment erosion rates. Water Air and Soil Pollution 1997;99(1-4):21-31. |
R825278 (Final) |
not available |
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Lick W, Chroneer Z, Rapaka V. Modeling the dynamics of the sorption of hydrophobic organic chemicals to suspended sediments. Water, Air and Soil Pollution 1997;99(1-4):225-235. |
R825278 (Final) |
not available |
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Roberts J, Jeppen R, Gothhord D, Lick W. Effects of particle size and bulk density on erosion of quartz particles. Journal of Hydraulic Engineering 1998;124(12):1261-1267. |
R825278 (Final) |
not available |
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Deane G, Chroneer Z, Lick W. Diffusion and sorption of hexachlorobenzene in sediments and saturated soils. Journal of Environmental Engineering 1999;125(8):689-696. |
R825278 (Final) |
not available |
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Jepsen R, Lick W. Nonlinear and interactive effects in the sorption of hydrophobic organic chemicals by sediments. Environmental Toxicology and Chemistry 1999;18(8):1627-1636. |
R825278 (Final) |
not available |
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Jepsen R, McNeil J, Lick W. Effects of gas generation on the density and erosion of sediments from the Grand River. Journal of Great Lakes Research 2000;26(2):209-219. |
R825278 (Final) |
not available |
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Lick W, McNeil J. Effects of sediment bulk properties on erosion rates. Science of the Total Environment 2001;266(1-3):41-48. |
R825278 (Final) |
not available |
Supplemental Keywords:
sediments, contaminated sediments, risk, transport and fate, hydrophobic organic chemicals, bioavailability, benthic organisms, erosion rates, deposition rates, modeling., RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Contaminated Sediments, Environmental Chemistry, chemical mixtures, Fate & Transport, Ecology and Ecosystems, fate and transport, aquatic life, biogeochemical partitioning, aquatic ecosystem, contaminant transport, erosion, predictive understanding, hydrophobic organic chemicals (HOCs), bioavailability, contaminated sediment, benthic biota, resuspension, sediment transport, transport contaminants, biota diversity, aquatic ecosystems, hydrophobic organic chemicals, ecology assessment models, aquatic biotaProgress and Final Reports:
Original AbstractThe 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.