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2003 Progress Report: Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II
EPA Grant Number: R828771C001Subproject: this is subproject number 001 , established and managed by the Center Director under grant R828771
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (2001) - Center for Hazardous Substances in Urban Environments
Center Director: Bouwer, Edward J.
Title: Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II
Investigators: Ball, William P. , Bouwer, Edward J.
Current Investigators: Ball, William P. , Bouwer, Edward J. , MacKay, Allison
Institution: Johns Hopkins University
Current Institution: Johns Hopkins University , University of Connecticut
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 2001 through September 30, 2007
Project Period Covered by this Report: October 1, 2002 through September 30, 2003
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001)
Research Category: Hazardous Waste/Remediation
Description:
Objective:The overall goal of this research project is to evaluate the need and develop the means to achieve improved modeling of the transport and fate of organic chemical contaminants as applied to risk assessment and management for contaminated sediments and soils. The specific objectives of this research project are to: (1) develop new data and modeling approaches toward better predictions of the combined effects of both sorption and biodegradation on organic contaminants, with a focus on solid phases typical of urban environments and on chemical fate in the presence of complex organic contaminant mixtures; (2) apply modeling simulations to evaluate the impact of nonlinear and competitive sorption on rates of desorption; (3) evaluate experimentally sources and mechanisms of nonlinear and competitive sorption in environmentally relevant solids; and (4) develop and evaluate alternative (mechanistically based) approaches for quantifying overall rates of desorption and biodegradation in contaminated soil/water environments that include complex mixtures of contaminants.
Contaminated sites typically involve complex mixtures of contaminants, the fate of which is affected by both biochemical interactions that impact microbial attenuation (e.g., cometabolic effects, competitive inhibition, and toxicity), as well as competitive adsorption on solid phases that can complicate mass transfer rates during desorption. Because sediment- or soil-bound contaminants usually are not bioavailable (from either a remediation or biotoxicity viewpoint), successful prediction and assessment of fate and transport require a full accounting and integration of the sorption effects. The solid phases from which desorption must be considered include sediments, surface soils, and subsurface geologic materials, all of which can contain substantial quantities of thermally altered or "black" carbon (BC), such as the chars, soot, and coals that are ubiquitous to urban environments. Such BC materials will tend to both strengthen the sorption effect and add complexity to our modeling approaches, especially under conditions of contamination by multiple chemicals in mixtures.
Progress Summary:This research project was accomplished primarily by a postdoctoral associate (Dr. Isam Sabbah)-approximately 55 percent time of his time was supported on this project between October 1, 2001 and June 15, 2002, with the remainder of his time supported by external funding from other ongoing projects. Dr. Sabbah came to Johns Hopkins University (JHU) from a research position with the Regional Research and Development Center of the Galilee Society, and has degrees in both chemical engineering (B.S.) and environmental engineering (M.Sc., Ph.D.), from the Israel Institute of Technology (Technion).
This research project involved two principal areas of effort: (1) the development and application of new computer models for considering the combined effects of sorption and diffusion on rates of contaminant desorption from sediments, including the coupling of such effects with aqueous processes of biodegradation; and (2) laboratory evaluation of selected Baltimore harbor sediments in regard to both their carbon content (and carbon type) as well as their sorption characteristics with respect to a probe nonpolar organic chemical (phenanthrene) to begin to assess the potential importance of sorption nonlinearity and competition in urban sediments.
Modeling
Modeling was conducted to better understand the role of nonlinear and nonequilibrium adsorption on long-term desorption and biodegradation. Numerical computer models were developed (based on modifications of models used in prior work) to simulate the combined effects of nonlinear adsorption isotherms and diffusion limitations on rates of contaminant desorption under hypothetical scenarios of sorption "loading" and desorption, assuming sorbing particles that are modeled after those previously studied in our laboratory (e.g., sediments from Bozeman, MT, and CFB Borden in Canada). More specifically, long-term desorption was considered for a "virtual" sediment-water-contaminant system, which involved a diffusion-limited nonlinear sorption isotherm and was subjected to simulated conditions of either short- or long-term periods of sorptive chemical uptake from solution. Simulated desorption data under the various uptake conditions (short-and long-term uptake) were interpreted with "best-fit" parameterizations of a diffusion rate model, using alternative assumptions about the equilibrium isotherm. Good fits of short-term rate data were possible in all cases, but models based on erroneous isotherms (as based on uptake experiments characterized by premature termination or insufficient range of concentration) caused severe errors in the prediction of long-term desorptive mass fluxes and rates of biodegradation. Results also illustrated how short-term sorption experiments can seem to be at equilibrium, yet lead to adsorption/desorption results that would be misinterpreted as "hysteretic," despite the intrinsic reversibility of the synthetic system. Some initial modeling also was conducted to illustrate how the desorptive fluxes could be integrated with fluid-phase biodegradation rates. The results of these modeling exercises have been presented at several conferences and a draft manuscript has been prepared for future publication, preferably in the journal Environmental Engineering Science.
The developed computer code has been carefully verified and documented in accordance with the quality assurance/quality control requirements of the project, and will be the basis for modeling in Phase II of the work, in which the competitive aspects of sorption and biodegradation also will be considered.
Laboratory Experimentation
Laboratory experimentation on this research project was originally envisioned to include application of a previously published method (Gustafsson, et al., 1997) to estimate BC content of field samples, including harbor sediments, brownfield soils, and other sites of contamination in urban settings, and to obtain screening-level sorption equilibrium and rate data using nonpolar organic chemical probes. Toward this end, a doctoral student (Ms. Thanh Nguyen, funded primarily by the National Science Foundation) implemented the Gustafsson, et al., technique in our laboratory, and conducted an evaluation of the method with regard to its ability to discern soot and char samples. Because early results were not encouraging, we expanded that study, and now have a very complete dataset relating to the method, with a paper of results in press (Nguyen, et al., 2003). Regrettably, these results indicate that the method will not provide unambiguous results about BC (and especially char) in soils and sediments. In Year 2 of the project, we obtained field samples of Baltimore harbor sediments, and conducted sorption equilibrium tests using nonpolar organic chemical probes.
Three samples of the Baltimore harbor sediments were collected as part of other ongoing research at the University of Maryland Chesapeake Bay Laboratory; these were kindly provided to us by Dr. J. Baker. (These samples were collected using a ship-deployed grab sampler that scoops up surface sediment from the top 10 to 20 cm. Once obtained, the sediment was thoroughly mixed, placed in glass jars, and frozen). In our laboratory, these sediments were air dried, and sieved through 250 mesh prior to analysis. The fraction of organic carbon content and the BC were determined using methods described elsewhere (Nguyen, et al., 2003), and preliminary phenanthrene sorption results were obtained using methods developed in our laboratory. For the sediment sample studied most extensively (from the Middle Branch of the Patapsco River), the two-point sorption of phenanthrene showed log Koc in the range of 4.4 to 4.7, which is slightly higher than would be expected for "normal" sediment organic matter (log Koc = 4.2); however, the difference was far below the order-of-magnitude differences sometimes observed with sediments containing similarly high fractions of soot carbon (11 percent of the total carbon in the sample was nominally identified as "soot carbon"). Additional studies with these and other sediments are required to more fully investigate the potential importance of sorption nonlinearity and sorption competition in urban sediments, but unfortunately, these studies could not be completed within the time and budget of Phase I.
Reference:
Gustafsson O, Haghseta F, Chan C, MacFarlane J, Gschwend PM. Quantification of the dilate sedimentary soot phase: implications for PAH speciation and bioavailability. Environmental Science and Technology 1997;31:203-209.
Future Activities:A Phase II study to build on the findings of this project is now underway, also under the auspices of the CHSUE. At the time of this report, this research project is still being staffed, but some of the intended future activities are briefly described below.
Modeling
Future modeling efforts will apply numerical models to evaluate the sensitivity of overall degradation rates to the presence of cocontaminants, with consideration of adsorption, diffusion, and biodegradation effects. We intend to survey selected Superfund sites in the region and conduct a literature review to select appropriate waste mixtures and model parameter values. Using these selected conditions as case studies, we intend to apply our models toward estimating the magnitude of effect that cocontaminants may have on both desorption and degradation under conditions of both batch experimentation and flow-through porous media. In addition to direct effects on biodegradation rates, competing cosolutes are expected to lead to more linear sorption during both sorption and desorption. The precise nature of these sorption effects is expected to be complex; however, owing to the fact that concentrations of all chemicals also will be affected by processes of intrasorbent diffusion and biodegradation.
Laboratory Experimentation
We intend to continue our investigation of the sorption of nonpolar organic chemical probes with selected samples of urban sediments and soils. Our emphasis will be on the characterization of the BC content and the overall role of competitive adsorption processes on observed sorption isotherms. Sediments from U.S. Environmental Protection Agency Regions 1, 2, and 3 will be sought, with an emphasis on integrating the results of this project to other ongoing Hazardous Substance Research Center research. The results of this research project will allow us to better relate our continuing modeling sensitivity exercises to actual case scenarios.
Journal Articles:No journal articles submitted with this report: View all 29 publications for this subproject
Supplemental Keywords:toxic chemicals, chlorinated organic chemicals, sorption, biodegradation, competitive adsorption, cleanup, restoration, hydrogeology, brownfield sites, HSRC, chemical contaminants, chemical exposure, chemical mixtures, co-contaminants, community support, complex mixtures, contaminant dynamics, contaminant transport, contaminated sediment, environmental hazards, environmental justice, exposure, exposure assessment, hazardous substance contamination, human exposure, human health risk, outreach and education, outreach material, risk assessment, sediment transport, sediment treatment, technical outreach, technology transfer, urban environment, urban sediment. , ENVIRONMENTAL MANAGEMENT, Water, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Scientific Discipline, Waste, Health, RFA, PHYSICAL ASPECTS, Brownfields, chemical mixtures, Remediation, Risk Assessment, Risk Assessments, Waste Treatment, Health Risk Assessment, Physical Processes, Hazardous Waste, Contaminated Sediments, Hazardous, Ecology and Ecosystems, environmental justice, exposure assessment, urban environment, Brownfield site, biodegradation, outreach material, brownfield sites, urban sediment, environmental hazards, co-contaminants, human health risk, technical outreach, contaminated sediment, outreach and education, community support, contaminant dynamics, contaminant transport, contaminated soils, sediment transport, chemical exposure, hazardous substance contamination, complex toxic chemical mixtures, exposure, sediment treatment, technology transfer, chemical contaminants, complex mixtures, human exposure, web development
Relevant Websites:
http://www.jhu.edu/hsrc 
http://www.jhu.edu/~dogee/people/faculty/ball.html
http://www.jhu.edu/~dogee/people/faculty/bouwer.html
Progress and Final Reports:
2002 Progress Report
Original Abstract
2004 Progress Report
2005 Progress Report
Final Report
Main Center Abstract and Reports:
R828771 HSRC (2001) - Center for Hazardous Substances in Urban Environments
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828771C001 Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II
R828771C002 The Fate and Potential Bioavailability of Airborne Urban
Contaminants
R828771C003 Geochemistry, Biochemistry, and Surface/Groundwater Interactions
for As, Cr, Ni, Zn, and Cd with Applications to Contaminated Waterfronts
R828771C004 Large Eddy Simulation of Dispersion in Urban Areas
R828771C005 Speciation of chromium in environmental media using capillary
electrophoresis with multiple wavlength UV/visible detection
R828771C006 Zero-Valent Metal Treatment of Halogenated Vapor-Phase Contaminants in SVE Offgas
R828771C007 The Center for Hazardous Substances in Urban Environments (CHSUE) Outreach Program
R828771C008 New Jersey Institute of Technology Outreach Program for EPA Region II
R828771C009 Urban Environmental Issues: Hartford Technology Transfer and Outreach
R828771C010 University of Maryland Outreach Component
R828771C011 Environmental Assessment and GIS System Development of Brownfield Sites in Baltimore
R828771C012 Solubilization of Particulate-Bound Ni(II) and Zn(II)
R828771C013 Seasonal Controls of Arsenic Transport Across the Groundwater-Surface Water Interface at a Closed Landfill Site
R828771C014 Research Needs in the EPA Regions Covered by the Center for Hazardous Substances in Urban Environments
R828771C015 Transport of Hazardous Substances Between Brownfields and the Surrounding Urban Atmosphere