592 (HAW-1122-310045) Biogeochemical Considerations for Model Predictions of Solute Biodegradation in Sorbent-Water Systems.
Start time: 1:50 PM
Haws, N¹, Bouwer, E¹, Ball, W¹, ¹ Johns Hopkins University
The bioavailability of a contaminant for microbial uptake (and thus the effectiveness of the bioremediation strategy) is dependent on how contaminants are sequestered by sediment particles and interact with co-existing solutes. It is therefore important to consider the biogeochemical conditions for which the contaminant(s) exist in order to understand how sensitive modeling predictions of bioremediation efficacy are to the assumptions inherent in the model formulation. In this study, a suite of numerical simulations of hypothetical batch system are conducted to investigate the sensitivity of different modeling approaches in simulating the bio-attenuation of co-existing solutes (TCE and toluene) in sorbent - water systems. The results are insensitive to the type of sorption model in systems with low sorption strength and slow biodegradation rates, and insensitive to the biodegradation rate model if mass transfer controlled. Also, differences among model results are generally greater when evaluated in terms of total mass removal rather than aqueous phase concentration reduction. In general, the fate of the cometabolite is more sensitive to the proper consideration of co-solute effects than is the fate of the primary substrate. A preliminary guide for assess such sensitivities for a given system is a graphical comparison of a characteristic mass transfer rate coefficient (mt) versus a characteristic biodegradation rate coefficient (bio). By indicating relative sensitivities to the different processes and how these sensitivities may be expected to change with time, this graphical approach can guide the selection of an appropriate level of model complexity needed to suitably predict bioremediation.

593 (ROC-1118-276452) Hydraulic Separation during Dredging Facilitates Cleanup of Contaminated Sediments.
Start time: 2:10 PM
Zhao, X¹, Drumm, L¹, Rockne, K¹, ¹ Department of Civil Engineering, University of Illinois, Chicago, Chicago, IL, USA
Past research in our laboratory has demonstrated that cleanup of the entire sediment may not be necessary due to sequestration of the vast majority of hydrophobic pollutants like PAHs into a hydraulically-separable low density fraction. In 2001, PAH-contaminated sediments from the Indiana Harbor and Canal were hydraulically dredged by the USACE to evaluate the Eddy dredge system and characterize water treatment needs in the entrained water separated in a settling basin. This project provided an opportunity to test our hypothesis that a fortuitous segregation of sediments would occur via hydraulic settling processes in the settling basin. Following decommission of the basin, sediment cores were collected to depths of approximately 20 cm from ten locations in the basin immediately after dewatering. Samples were separated into low and high density fractions. The separated fractions were characterized for the contents of organic matter (OM), organic carbon (OC), soot carbon (SC), and PAH concentration. As expected, sediments collected along a transect of the basin showed a large decrease in bulk density with increasing distance from the dredge outfall. PAHs were highly correlated with the fraction of low density material in the sediment and concentrations were highest (above 1000 ppm) in sediments further from the outfall. In contrast, the sediment close to the outfall had almost no low density material and had PAH concentrations well below sediment quality criteria. These results provide support for the concept that hydraulic dredging can result in a fortuitous separation of contaminated sediment with high amounts of low density material and high PAH concentrations from sediment meeting sediment quality standards.

594 (MUR-1118-278542) Bioremediation of weathered oil from the 1991 Gulf War.
Start time: 2:30 PM
Murphy, T¹, Shaw, R², Guo, J¹, Parr, T¹, Leppard, G¹, Blair, S³, ¹ Environment Canada, National Water Research Institute, Burlington, ON, Canada² Redlog Environmental Ltd, Bangrak, Bangkok, Thailand³ Consortium of International Consultants, Safat, Kuwait
In the 1991 Gulf War over 40 billion litres of oil were released. This oil spill was by far the largest in history. There are over 64 km2 of shoreline that are still contaminated. The anticipated recovery is taking about ten times longer than other studied oil spills. We were contracted by Consortium of International Consultants (CIC) from its client, Public Authority for Assessment of Compensation Resulting from Iraqi Aggression in the state of Kuwait (PAAC), to review the potential for bioremediation and to prepare submissions to the United Nations Claims Commission (UNCC). Only with nutrient enrichment were bacteria seen with an electron microscope to be commonly attached to oil. A pilot-scale injection of a solution containing nitrate and nutrients into intertidal sediments bioremediated highly weathered oil. After one month there was a notable production of alkanes resulting from either breakdown of larger more complex petroleum compounds or "liberation" of sequestered oil from a mineral precipitate matrix. Two months following the treatment, effectively all of the C8 to C40 compounds were reduced to very low levels equating to treatment effectiveness for aliphatics of about 90%. There was little washout of the nutrients. Impacts to benthos were limited and they fully recovered within three months.

595 (MON-1117-823640) Biodegradation of nitrogenous energetic compounds in coastal ecosystems.
Start time: 2:50 PM
Montgomery, Michael¹, Osburn, Christopher¹, Boyd, Thomas¹, Hamdan, Leila¹, Walker, Shelby¹, ¹ Naval Research Laboratory, Code 6114, Washington, DC, USA
Mineralization rates of nitroaromatic energetic compounds (NECs) in sediment were measured during surveys on eight research cruises. Surface sediments were collected over a three year period in Chesapeake Bay, San Francisco Bay, and two tropical locations off the coast of Oahu. Radiolabeled (¹⁴C) 2,4,6-Trinitrotoluene (TNT), 2,4-Dinitrotoluene (DNT), and 2,4-Diaminotoluene (DAT) was used in rapid (24 h) assays of submerged sediment and seawater to determine mineralization rates. Cruises conducted in September 2002, September 2003, and March 2004 in the Chesapeake Bay yielded the highest average NEC mineralization rates among the different locations, with average September 2003 values exceeding 0.25 g g^-1 day^-1. These mineralization rates were often an order of magnitude higher than those for three polycyclic aromatic hydrocarbons (PAHs), naphthalene, phenanthrene, and fluoranthene, despite the ubiquity of PAHs and the lack of known current inputs of NECs to the Chesapeake Bay system. The Pacific stations demonstrated significantly lower NEC mineralization rates, equivalent to PAH mineralization rates in the same locations. In general, mineralization rates of TNT were faster than those for DNT or DAT when comparing subsamples from the same location. Using natural bacterial assemblages from seawater collected during the March 2005 Chesapeake Bay cruise, it appears that this may be due to differential uptake and incorporation rate by bacteria which was greater for TNT than for either DNT or DAT. Despite the lack of exposure to exotic nitrogenous compounds, like TNT, natural assemblages may rapidly metabolize these compounds due to nitrogen limitation of bacterial growth in coastal estuarine and marine ecosystems.

(58156) Break.
Start time: 3:10 PM

596 (FEN-1117-737521) Exploitation of Dehalococcoides sp. for Dechlorination of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans.
Start time: 3:50 PM
Fennell, D¹, Liu, F¹, Son, E-K¹, ¹ Rutgers University, New Brunswick, NJ, USA
The exploitation of the dehalorespiring bacteria Dehalococcoides for use in detoxification of environmental media contaminated with polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) is being explored. D. ethenogenes strain 195 grows using the chloroethenes as electron acceptors and hydrogen as an electron donor. We previously reported that D. ethenogenes strain 195 dechlorinates a variety of chlorinated aromatic compounds, including 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD) and 1,2,3,4-tetrachlorodibenzofuran. The ability of D. ethenogenes to dechlorinate different PCDD/F congeners was investigated. Dechlorination of 1,2,3,4-TeCDD, octachlorodibenzo-p-dioxin (OCDD) and 1,2,3,4,7,8-hexachlorodibenzofuran (1,2,3,4,7,8-HxCDF) was examined in a mixed culture containing D. ethenogenes. An individual PCDD/F congener served as sole electron acceptor in one triplicate bottle set while tetrachloroethene (PCE) or 1,2,3,4-tetrachlorobenzene (TeCB) were added as growth co-substrates along with the PCDD/F congener in another two sets of triplicate bottles. The OCDD and 1,2,3,4,7,8-HxCDF were added at 5 M, PCE and TeCB were added at 25 M, and butyrate was added periodically at 0.1 mM as a hydrogen source. The mixed culture dechlorinated 1,2,3,4-TeCDD at similar rates both with and without the addition of PCE in original fully-grown cultures and in first generation transfer bottles which received 10 % inoculum. Dechlorination of 1,2,3,4,7,8-HxCDF produced a non-2,3,7,8-substituted penta-CDF congener within 1 month. Cultures co-amended with TeCB exhibited the most extensive HxCDF dechlorination with additional production of two non 2,3,7,8-substituted tetra-CDF congeners, one of which was tentatively identified as 1,3,7,8-TeCDF, within 2 months. No dechlorination products were observed from OCDD within the same time period. The dechlorination of a 2,3,7,8-substituted PCDF congener to non-2,3,7,8-substituted congeners by a D. ethenogenes-containing culture suggests that this strain may have utility in bioremediation efforts aimed at detoxifying PCDD/F-contaminated sediments.

597 (TAB-1118-252764) Microbial - Metal Interactions Affecting Bioremediation of Metal Contamination of Soils and Sediments.
Start time: 4:10 PM
Tabak, H¹, van Hollenbusch, E², Dejonghe, W³, ¹ US EPA, ORD, NRMRL, Cincinniti, OH, USA² Universite de Liomoges, Laboratoire des Sciences de l’Eau et de l’Environment, Limoges, France³ Flemish Institute for Technological Research, VITO, Belgium
The last 15 years have seen an increase in the types of contaminants to which bioremediation is being applied, including solvents, PAHs and PCBs. Now, microbial processes are beginning to be used in the cleanup of radioactive and metallic contaminants of soils and sediments. Microorganisms can interact with these contaminants and transform them from one chemical form to another by changing their oxidation state through the addition of (reduction) or moving (oxidation) of electrons. . In some bioremediation strategies, the solubility of the transformed metal or radionuclide increases, thus increasing the mobility of these contaminants and allowing them to more easily be flushed out from the environment. In other strategies, the transformed metal or radionuclide may precipitate out of the solution, leading to immobilization. Both kinds of transformations present opportunities for bioremediatioin of metals and radionuclides in the environments - either to immobilize or to accelerate their removal. Metal contamination of soils and sediments is especially problematic because of the strong adsorption of many metals to their particles. Due to the difficulty of desorbing metal contaminants, some traditional remediation methods, simply immobilize metals in contaminated soils, by the additioin of cement or chemical fixatives, by capping with asphalt, or by in-situ vitrification.. Alternatively, soils are often isolated by excavation and confinement in hazardous waste facilities. Although rapid in effect, both of these options are expensive and destroy soil’s future productivity. The success of soil washing and pump-and-treat technologies to remove metals is severely limited by the slow desorption kinetics of adsorbed metals, with the result that additional additives (acids, chelates and reductants) are often used to promote metal transfer to the aqueous phase. These agents improve cost effectiveness but may introduce further harmful chemicals. A primary strategy of bioremediation is the use of similar metal-immobilizing agents in conjunction with soil washing, with advantage that they pose no known environmental threat themselves. Biopolymers have been discovered that bind metals with high affinity and travel relatively unimpeded through porous medium. Certain mecroorganisms transform strongly-adsorbing metal species into more soluble forms and plants are being recruited that act as self-contained pump-and-treat systems. Other methods employ enzymatic activities to transform metal species into volatile, less toxic or insoluble forms. Techniques for soil bioremediation are usually designed to be used in-situ, lowering costs; they avoid the use of toxic chemicals, and in nearly all cases, the soil structure and potential for productivity are preserved. This review paper provides a detailed information on the metal-microbe interactions and the application of these interactions for bioremediation of the metal contaminated soils and sediments. The paper describes: (1) microbial processes effecting bioremediation of metals and radionuclides and influencing their toxicity and transport (metal biotransformation, metal biosorption, metal bioaccumulation and biomineralization via microbially-generated ligands - degradation and synthesis of organic ligands of toxic heavy metals); and (2) microbial mechanisms involwed in bioremediation of metal and radionuclide contaminated soils and sediments (dissimilatory metal reduction. microbial metabolism of iron bacteria, microbial metal leaching, microbial polymers and their use in bioremediation of metal contamination and microbial metal volatilization).

598 (REI-1118-350999) Mid-stream Assessment of the Active Capping Demonstration Project in the Anacostia River, DC.
Start time: 4:30 PM
Reible, D¹, Constant, W², Zhu, Y³, ¹ University of Texas, Austin, TX² Louisiana State University, Baton Rouge, LA³ Horne Engineering, Fairfax, VA
Innovative active capping techniques offering both containment and treatment are effective, low-cost means of managing the sediments that endanger the health of our nation=s waterways. The Active Capping Demonstration Project on the Anacostia River, Washington DC seeks to advance the implementation and acceptance of these under-utilized technologies by validating their efficacy at the Anacostia River where historic industrial, municipal, and military activities have resulted in toxic levels of PAHs, PCBs, metals, and other contaminants. Objectives are to demonstrate, on a field scale, the ability to design, construct and place caps that will provide long-term treatment of sediment contaminants while simultaneously providing containment. Cap materials placed include Aquablok, a commercial product designed to reduce the permeability at the sediment-water interface, apatite, designed to sorb or bind metals and coke, placed in a laminated mat to absorb organic contaminants. The materials were placed during April 2005 and sampling one month and six months after placement have been completed. The results from these early sampling rounds will be discussed. A third round of sampling will be conducted in September 2005 and preliminary results from that round of sampling will also be discussed. Supplemental sampling between these formal periods of analysis also provides some insight into processes at the site. Finally, ongoing laboratory experimentation to evaluate specific processes observed at field scale will also be summarized.

599 (SIM-1118-276961) Biodegradation and Sorption of TBA and MTBE in Near-Surface Sediments at a Full Scale Site in Wyoming.
Start time: 4:50 PM
Greenwood, M¹, Swank, A¹, McLean, J¹, Sims, R¹, ¹ Utah State University, College of Engineering, Logan, UT, USA
Natural recovery of TBA (tertiary butyl alcohol) and MTBE (methyltertiarybutyl ether) contaminated sediment was evaluated at a gasoline contaminated site located 60 miles north of Missoula, Montana in the town of Ronan along U.S. Highway 93. A LUFT at a refueling station released approximately 40,000L of gasoline from 1993 to 1994. A dissolved plume of MTBE and BTEX traveled underneath an alfalfa field and potentially discharges into Spring Creek located approximately 460 meters west of the spill site. Remediation activities began in 1995. Monitoring wells installed by the state of Montana DEQ showed MTBE concentrations from 8 mg/l at 200 meters west of the spill to 1 mg/l at 37 meters east of Spring Creek, to non-detectable levels at Spring Creek. The groundwater/surface water interface, or hyporheic zone, at this site provides an opportunity to evaluate the natural recovery of the sediments as ground water moves through this area. The purpose of this study was to evaluate biodegradation and sorption components for MTBE and TBA within the hyporheic zone sediments at the site. There is currently a lack of information concerning experimentally determined biodegradation rates and sediment sorption coefficients for these chemicals at full scale sites. Biodegradation rates and sorption coefficient are used in mathematical models of monitored natural attenuation for prediction of treatment times and for assessment of contaminants movement. Biodegradation rates currently available have been developed based on pure culture methods, and sorption coefficients have been primarily derived from prediction methods and have not been measured. This study also focused on the effects of specific environmental conditions, including dissolved oxygen status, temperature, and nutrient effects on biodegradation, and sediment organic matter content and effect of co-solutes on sorption. These factors were evaluated for the development of potential management strategies for enhancing the natural recovery of contaminated sediments at the Ronan site. Results indicated that both MTBE and TBA are biodegraded, and that the two compounds demonstrate different rates and different sorption patterns in the Ronan sediments. Both compounds were degraded under aerobic conditions. MTBE sorption isotherms developed showed a linear relationship for MTBE, and the value for the organic carbon distribution coefficient is an order of magnitude higher than those based on prediction methods that were identified in the literature and five times higher than predicted for TBA. Isotherms for TBA demonstrated a non-linear relationship of aqueous concentration to sorbed concentration at low TBA concentrations (ug/l levels). Results indicated that environmental variables have an effect on both biodegradation rate and extent of sorption, and therefore potential management strategies may be used to enhance the natural recovery of the contaminated sediments at the Ronan site.

600 (JAF-1117-818108) Effect of Plants on Sulfur Species and the Bioavailability of Trace Metals in Wetland Sediments.
Start time: 5:10 PM
Jaffe, P¹, Choi, H¹, ¹ Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA
The effects of oxygen release, evapotranspiration, and root exudation can influence sulfur dynamics in wetland sediments, which in turn is strongly coupled to the dynamics of trace metals. To gain a better understanding how the presence of plants and their seasonal growth cycle affects the biogeochemistry of sulfur species in wetland sediments, and how this in turn relates to the mobility of heavy metals, we conducted comparative in situ measurements between vegetated and non-vegetated sediments. Results show that in the presence of plants, sediments had substantially elevated SO42- concentrations in the rhizosphere during the growing season, ranging from 0.2 mmol/l to 6.20 mmol/l, with the highest increases occurring early during the growing season. The sulfide mass in the sediments, measured as AVS, showed that the AVS pool is sufficient to account for the increase in the SO42- concentration in the sediment pore water during the beginning of the growing season, and that the AVS pool was significantly higher in the vegetated sediments. Evapotranspiration is a major contributor in the transport of SO42- and trace metals from the overlaying water column into the sediments. The results from our measurements show that AVS and AVS associated zinc, cadmium, and lead penetrate deeper into vegetated sediments, where they are expected to be less vulnerable to erosion processes or to the exposure to air during low-flow conditions. The AVS to trace-metal ratio in the sediments was sufficiently high so the trace metals are considered to be non-bioavailable, even during the early growing season when a fraction of the AVS is reoxidized.