Grantee Research Project Results
2002 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: Center for the Study of Childhood Asthma in the Urban Environment
Center Director: Hansel, Nadia
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: The Johns Hopkins University
Current Institution: The Johns Hopkins University , University of Connecticut
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2001 through September 30, 2007
Project Period Covered by this Report: October 1, 2001 through September 30, 2002
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The overall objective of this research project is to evaluate the need and develop the means to improve modeling of the transport and fate of organic chemical contaminants, as applied to risk assessment and management for contaminated sediments and soils. We also want to develop new data and modeling approaches that can be applied 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. The specific objectives of this research project are to: (1) apply modeling simulations to evaluate the impact of nonlinear and competitive sorption on rates of desorption; (2) experimentally evaluate sources and mechanisms of nonlinear and competitive sorption in environmentally relevant solids; and (3) 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), and 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:
Our proposed experimental approach for this project is based on a combination of computer modeling and laboratory evaluation. In the subsections below, we briefly describe our progress in each of these two areas.
Modeling. Modeling has been conducted to better understand the role of nonlinear adsorption on long-term desorption and biodegradation. This effort has been accomplished primarily by a postdoctoral associate (Isam Sabbah) who has devoted approximately 50 percent of his time to this project since his arrival at Johns Hopkins University (JHU) in late October 2001. Dr. Sabbah came to 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). While working on this project, Dr. Sabbah made progress on the development of numerical computer models 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 Canadian Forces Base Borden, Ontario, Canada). More specifically, "known" nonlinear equilibrium isotherm information and intraparticle diffusion rate constants for these materials have been used to conduct alternative model simulations of long-term contaminant desorption and bioavailability, as based on model formulations and parameterizations that might be obtained from both short-term and longer-term sorption uptake experiments. We have explored the extent to which sorption nonlinearity and a failure to experimentally evaluate truly long-term equilibrium can lead to an inaccurate estimation of rate parameters and subsequently inaccurate predictions of biodegradation and desorption. The results obtained to date have shown that desorptive mass flux can be extremely sensitive to the "perceived" reality of the sorption isotherm. Because desorptive mass flux is an important determinant of contaminant persistence at waste sites, very careful experimentation will be required to fully understand long-term and non-linear contaminant distribution. The computer code that has been written will be the basis for future work in which competitive sorption is introduced.
Laboratory Experimentation. In regard to laboratory experimentation, our proposed approach focused on the 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 obtain screening level sorption equilibrium and rate data using nonpolar organic chemical probes. Toward this end, a doctoral student (Thanh Nguyen) has fully implemented the Gustafsson, et al., approach in our laboratory and has been conducting an evaluation of the method with regard to its ability to discern soot and char samples. Because early results were not encouraging, we have had to expand that study. We now have a very complete data set relating to the method. Regrettably, these results have caused us to believe that the method will not be able to provide unambiguous results about BC (and especially char) in soils and sediments. We intend to proceed with an evaluation of sorption properties on some selected field samples in Year 2 of the project. However, given our results with the BC method, these sorption results will now be viewed as examples for our modeling exercise, with less emphasis on integrating the BC measurement into the modeling approach.
Future Activities:
Future activities for this research project involve additional modeling and experimentation.
Modeling. Future modeling efforts will apply postulated numerical models to evaluate the sensitivity of overall degradation rates to both biochemical issues and nonlinear adsorption effects. We intend to survey selected Superfund sites in the region for waste mixtures and model parameterizations. Using these selected conditions as case studies, we intend to apply our models toward estimating the magnitude of the effect that co-contaminants may have on both desorption and degradation. In addition to direct effects on biodegradation rates, competing co-solutes are expected to lead to more linear sorption during both sorption and desorption. However, these effects are too complex to understand without modeling because concentrations also are controlled by processes of intrasorbent diffusion.
Laboratory Experimentation. We intend to obtain field samples of harbor sediments and Superfund site soils and, if constraints of personnel time and budget permit, we intend to conduct screening level sorption equilibrium and rate tests using nonpolar organic chemical probes. Our emphasis will be on testing for sorption nonlinearity and competition. The results of this work 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 subprojectSupplemental Keywords:
toxic chemicals, chlorinated organic chemicals, sorption, biodegradation, competitive adsorption, cleanup, restoration, hydrogeology., RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, INTERNATIONAL COOPERATION, ENVIRONMENTAL MANAGEMENT, Waste, Water, TREATMENT/CONTROL, Waste Treatment, Contaminated Sediments, Remediation, Health Risk Assessment, chemical mixtures, Risk Assessments, Brownfields, Hazardous Waste, Physical Processes, Ecology and Ecosystems, Hazardous, Risk Assessment, brownfield sites, environmental hazards, outreach material, complex mixtures, sediment treatment, chemical exposure, contaminant transport, contaminant dynamics, environmental justice, risk assessment , biodegradation, contaminated sediment, sediment transport, exposure, Brownfield site, chemical contaminants, human exposure, co-contaminants, urban sediment, complex toxic chemical mixtures, outreach and education, technology transfer, urban environment, human health risk, web development, technical outreach, community support, hazardous substance contamination, exposure assessmentRelevant Websites:
http://www.jhu.edu/hsrc Exit
http://www.jhu.edu/~dogee/people/faculty/ball.html Exit
http://www.jhu.edu/~dogee/people/faculty/bouwer.html Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R828771 Center for the Study of Childhood Asthma in the Urban Environment 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
The 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.
Project Research Results
5 journal articles for this subproject
Main Center: R828771
108 publications for this center
20 journal articles for this center