D. Ringelberg, and M. Reynolds, U.S. Army Engineering Research and Development Center, and A. Peacock, University of Tennessee/Center for Biomarker Analysis

As part of a recent USACE effort, dredged harbor sediment contaminated with polycyclic aromatic hydrocarbons (PAHs) was removed from the Milwaukee Confined Disposal Facility near the South Milwaukee Harbor, WI, and examined for in situ biodegradative capacity. By integrating analytic chemistry, microbiology, and molecular biology techniques, the successional characteristics of indigenous microbiota were determined during a four-month bioslurry evaluation. Total PAH concentrations were reduced by 51% in the first two months of the evaluation followed by only an additional 1% in the next two consecutive months. The plateau in PAH loss was preceded by a shift in the microbial phenotype and genotype toward one conducive to PAH biodegradation (specifically toward the presene of the Rhodococcus sp. of bacteria and enzymatic catabolism via aromatic ring cleavage). A similar approach was taken to examine the RDX biodegradative capacity of an Arctic soil over a 5 week period. A significant loss in RDX concentration only occurred if the soil was submerged under water for the duration of the study. The reduced environment was then further manipulated by the addition of alternative e^- acceptors, which induced a change in the in situ microbial community structure resulting in different rates and extents of RDX transformation. RDX transformation/biodegradation occurred at the greatest rates and extents in the order: iron (in the zero valent stae) > sulfate > nitrate. Results of these studies suggest that the intrinsic biodegradative potential of an environmental site can be derived from the polyphasic characterization of the in situ microbial community. The integrated approach outlined above focuses on the use of "whole-sample" characterization techniques or direct assays of microbes in their natural environments, without impacting them during the measurement process. In addition, these techniques collectively provide the activity measurements or phenotypic/genotyic descriptions necessary for defining in situ biodegradation potentials, which no single assay can address.

Michael T. Montgomery, Thomas J. Boyd, and Chris Osburn, Naval Research Laboratory; Julia K. Steele and Catherine V. Badger, Geo-Centers, Inc, Washington, DC.

Polycyclic aromatic hydrocarbons are a prevalent source of toxicity in estuarine sediments. Chronic exposure to petroleum hydrocarbons may result in alteration and adaptation of the natural bacterial assemblage in these sediments. During five research cruises from November 1999 to August 2001, surface sediments were sampled at 11 stations in the Elizabeth River and Lower Chesapeake Bay. Bacterial production and mineralization of sentinel PAHs (naphthalene, phenanthrene, and fluoranthene) were measured in sediment subsamples using radiotracer additions. Ambient PAH and lignin concentrations were also measured in the sediment for comparison with the microbiological parameters. We found that PAH mineralization rates typically varied by four orders of magnitude over the survey site with the lowest mineralization occurring at the offshore station and the highest mineralization in sediments that were chronically exposed to petroleum hydrocarbons from groundwater intrusion. Phenanthrene and fluoranthene mineralization rates were frequently higher than those measured for naphthalene. Ambient total PAH concentrations in the sediments varied from less than 1.0 m g g^-1 sediment dry weight to over 13 m g g^-1 over the survey site. The range of values for bacterial production, PAH mineralization and ambient PAH concentrations were similar to that measured in both the Charleston Harbor and the Upper Delaware Bay/Schuykill River systems. Comparing PAH mineralization rates to total heterotrophic production is proposed as a line of evidence for naturally attenuating sediments.

Danny Reible, PhD, PE, and X. Fu, Louisiana State University

Capping with clean sediments is an effective means of managing contaminated sediments. A simple analytical model of chemical migration in caps has been proposed (Reible, in Palermo et al., 1998) to aid in their design and evaluation. Due to the long time frames normally required to evaluate capping effectiveness in the field, a laboratory study was initiated to test and refine the model using high precision vertical profiling of toluene transport in a sorbing cap. Models for both cap consolidation and chemical transport were considered. The Corps of Engineers model PSDDF was found to adequately describe subaqueous consolidation of a cap while the chemical transport and fate model was found to accurately describe chemical transport during and subsequent to consolidation. Experimental results and model comparisons will be presented and the capabilities of the current version of the model reviewed.

P.R. Jaffe, S. Xu, and J.H. Choi, Princeton University

Ralph J. Portier, Ph.D., Patrick. M. Moore, R.Mark Conger, Louisiana State University

New industrial construction projects along the Mississippi corridor often require demolition of existing structures and subsequent site assessment and remediation of deltaic soils/sediments and groundwater. This can be a challenging endeavor that often involves excavation of site materials and off site transport. New methods are needed that do not require excavation and that can treat marginally contaminated sites in place. A remediation alternative utilizing a biological in situ process ,i.e., biological plugs, was evaluated as a sound, low intervention strategy. This low intervention, biological plug strategy was utilized to treat petroleum contaminated soil, impoundment sediments and groundwater in order to ready a site for a new construction project. Initial total petroleum hydrocarbon (TPH) soil measurements revealed values as high as 5200 mg/kg. Groundwater TPH measurements revealed concentrations as high as 20 mg/L. The goal of this project was to reduce these concentrations to that deemed suitable by state risk assessment standards (2.7 mg/L groundwater). By the end of a 220 day treatment period, all TPH concentrations had been reduced to concentrations well below regulatory standards. Soil TPH and groundwater concentrations had been reduced to non detect at six of the seven sampling locations. TPH concentrations at the remaining sampling location was 150±22 mg/kg for TPH _soil and 0.15± 0.1 mg/L TPH _groundwater.

Michael F. Coia, URS Corporation and Dr. Laura Carreira, Applied PhytoGenetics, Inc.

Phytoremediation is presently gaining increasing technical and regulatory acceptance as an environmentally sound and cost-effective solution for the in-situ cleanup of organics-contaminated wetland sediments, surface water and shallow ground water. The selection and application of native plant species to phytodegrade organic constituents of concern represents a successful biotechnology alternative to conventional site cleanup techniques. While many phytoremediation applications involve hydraulic control of ground water plumes using tree stands or incorporate increased bio-accumulation of metals constituents from soils requiring subsequent plant harvest, this paper addresses successful treatment of specific organic contaminants using proper plant selection and design of wetland ecosystems. These treatment wetlands utilize plant-based enzymatic biochemical processes, which work in concert with indigenous microbial activity to optimize rhizospheric biodegradation and plant tissue phytodegradation. The application of proper site design facilitates the combination of sediment cleanup with wetlands restoration for increased eco-habitat creation. The authors have teamed together at numerous sites to achieve successful treatment of site organics through monitored phytodegradation in laboratory greenhouse studies followed by field-scale site demonstrations and full-scale wetland phytoremediation systems. Data will be presented from recent projects involving the phytoremediation of contaminated sediments and shallow ground water plumes with elevated concentrations of chlorinated solvents, nitroaromatics and PAHs. These families of organic constituents are being successfully treated using engineered wetland phytoremediation systems. The biochemical kinetics of organics treatment will be presented as an important criterion for proper plant species selection. Recent advances in plant assay techniques along with laboratory greenhouse studies and field demonstrations allow for optimization of phytoremediation approaches, and these scientific techniques will be discussed. Practical engineering, design and field construction techniques will be presented, as they are successfully being employed in wetland phytoremediation systems for organics treatment. In order for phytoremediation of organics to achieve widespread application, successful site cleanup projects will require comprehensive interdisciplinary approaches, which involve biochemistry, plant molecular biology, botany, hydrogeology, ecological risk assessment, engineering and environmental landscape contracting. The importance of each of these project disciplines will be discussed.

Joseph P. Schubauer-Berigan, USEPA, ORD, NRMRL, Keith B. Lodge and Subhash C. Basak, University of Minnesota

The National Research Council has examined the availability of toxicity endpoints for industrial chemicals and concluded that many of these chemicals lack even minimum testing. One way of carrying out risk assessments of chemicals having insufficient experimental data is by using Quantitative Structure Activity relationship (QSAR) models and SARs. In this study we examined the toxicity and degradability of Quadricyclane and six of it’s analogs selected using Quantitative Molecular Similarity Analysis (QMSA) to evaluate the usefulness of this approach for chemical risk assessment. The degradability of these chemicals was examined in spiked water and sediments collected from a freshwater and marine location, under a variety of test conditions (abiotic, biotic, aerobic and anaerobic). The sediments water used in the experiments were thoroughly characterized for their physical, chemical and biological properties (e.g. salinity, OM content, nutrients, bacterial numbers etc.). The toxicity of the chemicals was examined using a number methods of commonly used in the literature for this purpose (BODs, Microbial Plate Counts, and Microtox). In addition, a novel new approach was developed using Biolog Microplates to examine the effect of these chemicals on substrate utilization patterns of natural microbial communities from the sampling locations. Results of the studies indicated that large fraction of the degradation of Quadricyclane and its analogs occurred primarily abiotically. The rate of chemical degradation and toxicity was influenced by the collection site of the exposure matrix. The chemicals tested resulted in altered microbial substrate utilization patterns compared with natural unexposed communities. The results of the degradability and toxicity studies verified the usefulness of QSAR, SARs and QMSA for risk assessments of chemicals having insufficient experimental data.