D. W. Moore, Ph.D., MEC Analytical Systems, Inc.

Sediment toxicity tests have become an integral component of environmental assessments. Toxicity and bioaccumulation testing is a feature of many regulatory programs in the U.S. (e.g., CWA, FIFRA, TSCA, CERCLA/SARA, RCRA, MPRSA). Numerous sediment bioassays have been developed for a variety of purposes. Most of these bioassays have been designed to assess the toxicity and/or bioaccumulation potential of sediments to make regulatory-based decisions (e.g., identifying acceptable disposal alternatives for dredged material; determining cleanup levels; or evaluating the effectiveness of the cleanup remedy). Since sediments serve as the ultimate repository for many environmental contaminants, the use of sediment bioassay as a tool in site assessment and site remediation/management activities logically follows. However, these bioassays should not be applied without proper consideration of the strengths and weaknesses of the individual procedures. This presentation will provide an overview of the general types sediment toxicity and bioaccumulation potential testing procedures currently available. Procedures to be discussed will range from standard bedded sediment and elutriate tests to more specialized techniques such as the sediment water interface test. A discussion of the strengths and weaknesses of individual procedures in context of the potential application to site assessment, remediation/management, and post-remediation/management monitoring will be included.

Joseph M. Jersak, Ph.D., CPSS, Hull & Associates, Inc.

Once sediment contamination has been discovered at a site, the need to characterize the full nature and spatial extent of contamination – that is, the extent of its vertical as well as lateral distribution – is often subsequently required in order to make appropriate and cost-effective, risk management-based decisions for the site. A logical, step-wise approach should be followed for characterizing the spatial extent of sediment contamination. This paper briefly summarizes a step-wise and iterative approach – the Data Quality Objectives (or DQO) Process – that may be used to develop a resource-effective sampling and analysis plan for adequately characterizing the spatial extent of biologically relevant sediment contamination at an impacted site; a general example of application of the DQO process for characterizing the spatial extent of biologically relevant sediment contamination within a dynamic riverine environment is also included. Finally, the roles that site-specific information, the conceptual site model, and statistical considerations collectively play in developing a sampling and analysis plan consistent with the DQOs are also briefly discussed.

Dr. Tom Murphy, Research Scientist; Environment Canada National Water Research Institute; Mr. Jay Babin, Senior Scientist, BTG-Golder Company Ltd.; Mr. Brian C. Senefelder, CHMM, Senior Scientist, Golder Associates Inc

Contaminated sediment and waterways are a major problem in many areas of the world. The USEPA has estimated that 10% of the nation's lakes, rivers, bays, and harbors have contaminated sediment that kill fish, harm fish-eating animals, and/or adversely impact human health. Sediment treatment options include dredging, physical and chemical capping, and in-situ sediment treatment. In our studies, in-situ sediment treatment has been used to oxidize sediment sulfides, control eutrophication and bioremediate organic contaminants. Sediment contamination of various types in freshwater and marine environments was studied in 22 sites from 6 countries in North America, Europe and Asia. The acceptance of in-situ sediment treatment and aquatic treatment technology has increased over the last few years and is expected to continue increasing. In-situ sediment treatment involves direct chemical injection into sediments to facilitate a chemical, physical or biological change in the sediment and contaminants. In-situ sediment treatment may offer a lower cost alternative or complement to dredging, confinement or off-site treatment and disposal for environmental restoration or waterfront development projects.

An in-situ sediment treatment technology has been developed and patented by the National Water Research Institute of Environment Canada. Golder Associates is licensed for the commercial application of the Limnofix In-Situ Sediment Treatment Technology. An overview of the development, applications and performance of this technology in Canada, Asia and the United States will be presented.

This work applied new investigative techniques to assess the locations, distributions, and associations of polycyclic aromatic hydrocarbons (PAHs) in dredged harbor sediments. Dredged materials from the Milwaukee Confined Disposal Facility and Harbor Point New York were collected and homogenized to provide sufficient sample for bioslurry treatment testing and for PAH analyses on various size and density fractions before and after biotreatment. Sediment PAH analyses included both whole-sample measurements and, most importantly, the determination of PAH distribution by sediment particle size and type. Physicochemical analyses included room temperature Tenax bead aqueous desorption experiments and thermal program desorption-MS studies to assess PAH sequestration energies on sediment particle types. Thermal programmed desorption-MS experimental protocols and data reduction techniques were developed to evaluate apparent PAH sequestration energies on sediment particles. Microbial ecology testing used polar lipid fatty acid (PLFA) and DNA procedures and radiolabel microcosm studies. Earthworm bioassays studied PAH bioaccumulation from untreated and biotreated PAH-impacted dredged materials. Overall, the results were used to synthesize and correlate data to assess the availability and treatability of PAHs in dredged sediments. The benefits of this work include: improved assessment of toxicity and risk for PAH contaminants in sediments by use of particle-scale techniques to assess PAH distribution and behavior; improved assessment for the potential success of biotreatment through understanding of factors contributing to available and unavailable PAH fractions; improved decision making regarding sediment quality criteria for PAHs and the biotreatment of PAH-impacted sediments; and reduced treatment costs and greater likelihood for reuse of dredged sediments through knowledge of the underlying processes affecting PAH locations, availability, treatability, and toxicity.

R. Ravikrishna, Louisiana State University, C.B.Price, US Army Corp of Engineers, J.M.Brannon, US Army Corp of Engineers, S.Yost, US Army Corp of Engineers, K.T.Valsaraj, Louisiana State University and L.J.Thibodeaux, Louisiana State University

The loss of volatile contaminants from dredged sediments is an increasingly recognized environmental problem. Dredging and storage operations in confined disposal facilities (CDFs) can increase the potential opportunity for VOC emission. Volatile emissions of organic contaminants and other odorous compounds that potentially reduce air quality are a concern. The US Army Corp of Engineers Waterways Experiment Station, Vivksburg, MS, in conjunction with Louisiana State University, Baton Rouge, LA, has completed laboratory investigations that measure volatile emissions of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), total recoverable petroleum hydrocarbons (TRPHs), ammonia, methyl mercaptans, and hydrogen sulfide from Indiana Harbor sediment. Emphasis is on trends in volatile emissions as a function of evaporative sediment drying, "wet/dry" cycles, and sediment disturbance. A comparison of measured laboratory fluxes of selected PAH compounds with those predicted by theoretical models and emission from spiked sediment are also presented. Tests were conducted using VOC flux chambers. Air was passed over the sediment surface at 1.7 L/min. The flow rate was chosen to eliminate the air-side transport resistance, thereby maximizing contaminant fluxes. Contaminant specific sampling tubes were attached to the chamber exit ports. The experiment was designed to provide information on maximum contaminant fluxes expected under different air humidity, sediment moisture and site management conditions which might occur during CDF operations. The sample schedule consisted of five continuous runs simulating various conditions. Consolidated samples of Indiana Harbor sediment were studied. Naphthalene and acenaphthene showed the highest initial volatilization rates of 50 and 6.7 ng/cm2hr, respectively. Most of the PAHs exhibited initial sharp decreases in flux rate within the first 72 hours following passage of dry air over the sediment surface in Run I. No increase in flux of any of the hydrocarbons was noted until test Run IV, when the sediment was reworked. The TRPH flux rate decreased from 500 to 175 ng/cm2/hr in 168 hours followed by an increase in rate to 867 ng/cm2/hr when humid air was passed over the sediment. A large flux of TRPHs apparently occurred during reworking of the sediment. Approximately 34,000 ng/cm2/hr TRPHs volatilized during a 20-minute mixing interval. PCB 1248 was the only arochlor detected during the experiment. The initial flux rate was 0.23 ng/cm2/hr and decreased to 0.06 ng/cm2/hr at 240 hours of sampling. Results of this investigation showed the highest contaminant fluxes occur with initial loading and mechanical disturbance of the sediment. Results imply the wetting of the sediment will not drastically increase emission rates. Measured fluxes were orders of magnitude lower than model predictions.

Cary T. Chiou, U.S. Geological Survey

The partition behavior was determined for three polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene, phenanthrene, and pyrene, from water to a range of soil and sediment samples. The measured partition coefficients of the individual PAHs between soil/sediment organic matter (SOM) and water (i.e., Koc's) are relatively invariant either for the "clean" (uncontaminated) soils or for the "clean" sediments; however, the mean Koc's on the sediments are about twice the values on the soils. This disparity conforms to the earlier observation for other nonpolar solutes and reflects the compositional differences between soil and sediment organic matters. No significant differences in Koc are observed between a "clean" coastal marine sediment and freshwater sediments. The coastal sediments that are significantly impacted by organic contaminants exhibit higher Koc values. At given Kow's (octanol-water), the PAHs exhibit much higher Koc's than other relatively nonpolar solutes (e.g., chlorinated hydrocarbons). This effect is shown to result from the enhanced partition of PAHs to SOM rather than from lower Kow's of PAHs at given supercooled-liquid solute solubilities in water. The enhanced partition of PAHs over other nonpolar solutes in SOM accounts for the markedly different correlations between log Koc and log Kow for PAHs and for other nonpolar solutes. The improved partition of PAHs in SOM stems apparently from the enhanced compatibility of their cohesive energy densities with those of the aromatic components in SOM. The approximate aromatic fraction in soil/sediment organic matter has been assessed by solid-state 13C-NMR spectroscopy.

Henry H. Tabak, U.S. EPA, Rakesh Govind, Makundan Ramani, University of Cincinnati

Restoration of contaminated sediments involves either mechanical removal of the sediment followed by treatment or in-situ treatment of the contaminants. Even after mechanical removal, considerable residues of the polluted material usually remain which require some form of in-situ treatment for eventual restoration. For in-situ treatment, conditions that appear to be rate determining are: (1) availability of oxygen; (2) availability of nutrients; and (3) nature of contaminants and sediment properties.

There are significant variations in the redox potential of sediments as a function of depth. Aerobic bacterial biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) is widely known and has been well studied. PAHs exhibit high octanol/water partition coefficient (K_OW), which results in the accumulation of these compounds in fatty tissues with subsequent biomagnification in the food chain.

In this paper bench-scale evaluation of two novel methods for in-situ biorestoration of contaminated sediments will be presented. The first method involves the use of specially designed polymeric membranes for controlling the redox potential in contaminated sediments. The method allows in-situ biodegradation of PAHs in contaminated sediments while preventing the membranes from fouling. Experimental data will be presented on biodegradation rates of 18 PAHs ( 2 ring to 6 ring compounds) as a function of redox potential using PAH-contaminated New York Harbor sediment. The rate of biodegradation decreased with increasing ring size and decreasing oxidation potential. Biodegradation of PAHs was achieved under membrane-controlled aerobic, anaerobic, sulfate-reducing and denitrifying conditions. Experimental testing of the synthetic membranes showed that in-situ PAH degradation could be increased several fold by utilizing the membranes to increase the sediment oxidation potential. The membrane technology is widely applicable for in-situ biotreatment of contaminated freshwater and marine sediments.

Another in-situ method for biorestoration of contaminated sediments involves bioaugmentation and/or biostimulation. Conventional methods for implementing bioaugmentaion by injecting acclimated microorganisms suffers from physical washout of the active cultures and competition from indigenous microbiota. Encapsulating acclimated selective bacterial cultures in specially formulated silica gel beads, which overcomes the above problems, has been successfully tested at the bench-scale. Results will be presented on these tests in this paper. The silica gel beads can also be used for biostimulation, by encapsulating specially formulated nutrients which are released slowly to the indigenous bacterial cultures.

The treatment costs for in-situ biorestoration of contaminated sediments using semi-permeable membranes and silica gel beads are compared to other treatment approaches.