2005 Progress Report: Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II

EPA Grant Number: R828771C001
Subproject: 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: The Johns Hopkins University
Current Institution: The Johns Hopkins University , University of Connecticut
EPA Project Officer: Klieforth, Barbara I
Project Period: October 1, 2001 through September 30, 2007
Project Period Covered by this Report: October 1, 2004 through September 30, 2005
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


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 (which can complicate mass transfer rates during desorption). Because sediment- or soil-bound contaminants are usually 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.

With the above as background, the overall goal of this research is to evaluate when a specific consideration of chemical interactive effects is needed (as a function of site conditions) and to develop and test improved models for simulating and predicting contaminant transport and fate under conditions that involve multiple chemical contaminants or additives. The phase II objectives are 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. Specific sub-objectives of the work are: (1) apply modeling simulations to evaluate the impact of co-contaminants on sorption and on rates of desorption and biodegradation; (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 mixtures of contaminants. The first year of effort was restricted to model review and development. The second year of effort is described below. The project is now in a period of no-cost extension through September 30, 2006, and we currently envision that funds will be fully expended by January 31, 2006, at which time all work under this grant will be complete.

Progress Summary:

In Year 2 of this project, we continued with our modeling efforts and also began some laboratory experiments. The purpose of the modeling work was to better understand how sorption, mass transfer, biodegradation and the presence of other compounds affect the fate of contaminants in sorbent-water batch systems. The context of this modeling work was the simultaneous (cometabolic) biodegradation of toluene and TCE in several hypothetical, yet realistic sorbent-water batch systems. The study considered how the biogeochemical conditions of the system influenced the sensitivity to the model framework. For example, in certain biogeochemical settings a model may need to account for complex sorption, mass transfer, biodegradation and/or co-solute effects while in other settings, simple first-order approaches may capture the system behavior. We also developed “bioavailability plots” by graphing the apparent mass transfer rate against the apparent biodegradation rate. These plots can serve as a means to show the process(es) limiting contaminant removal and as a practical guide to determining the process most affecting modeling results. The bioavailability plots also illustrate the timedependency of mass transfer and biodegradation rates in complex systems. This work was presented at the 2004 Fall Meeting of the American Geophysical Union and is currently in press for publication in Advances in Water Resources.

The laboratory work concentrated on developing a better understanding of the mass transfer constraints of solute availability. Experiments were conducted using a “macropore column”: a soil column constructed to have a central region of highly permeable sand surrounded by an annulus of a virtually impermeable silty-clay. The macropore column allowed us to test the effects different flow velocities on the diffusion of solute into a low permeability region. The experiments also followed-up on previous studies conducted with macropore columns by current and former students at Johns Hopkins University. Our preliminary findings are showing that the apparent diffusion rate coefficient scales with velocity. Our working hypothesis to explain this phenomenon involves two components: (1) at lower velocities, the solute concentration within the macropore region becomes more nonuniform, due to slower rates of axial dispersion (i.e. radial dispersion is no longer orders of magnitude greater than diffusion); and (2) at higher velocities, longitudinal advection in the annular region increases apparent mass transfer rates. Because neither of these effects is directly accounted for by the current model formulation (which assumes radially uniform concentrations in the macropore and negligible advection in the annulus), the changes in effluent concentration can only be simulated through incorrect adjustments to the fitted tortuosity factor. Work is on-going (by a research team led by Prof. Markus Hilpert of DoGEE) to apply pore-scale Lattice-Boltzmann simulations as a means to better simulate and understand the actual pore-scale water flow and solute transport and to thereby independently test the two components of our hypothesis.

Future Activities:

As the project draws to a close under a no-cost extension, our immediate activities will concentrate on finishing the macropore column laboratory experiments and their associated modeling and on publishing and presenting the work done to date. Currently we are planning to present at the annual meeting for the Society of Environmental Toxicology and Chemistry (SETAC) in November 2005 and the Fall meeting of the American Geophysical Union (AGU) in December 2005. Manuscript preparation and submittal for the work with the macropore column is a goal for the immediate future. Additional laboratory and field experiments still need to be conducted to better elucidate co-contaminant effects on risk and remediation under realistically complex field conditions (e.g. aquifer heterogeneity, unknown site history, unknown contaminant distribution, etc.).

Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other subproject views: All 29 publications 5 publications in selected types All 5 journal articles
Other center views: All 108 publications 22 publications in selected types All 20 journal articles
Type Citation Sub Project Document Sources
Journal Article Haws NW, Ball WP, Bouwer EJ. Modeling and interpreting bioavailability of organic contaminant mixtures in subsurface environments. Journal of Contaminant Hydrology 2006;82(3-4):255-292.
abstract available   full text available
R828771C001 (2004)
R828771C001 (2005)
R828771C001 (Final)
  • Abstract from PubMed
  • Full-text: Science Direct Full Text
  • Other: Science Direct PDF
  • Journal Article Haws NW, Bouwer EJ, Ball WP. The influence of biogeochemical conditions and level of model complexity when simulating cometabolic biodegradation in sorbent-water systems. Advances in Water Resources 2006;29(4):571-589.
    abstract available   full text available
    R828771C001 (2005)
    R828771C001 (Final)
  • Full-text: Science Direct Full Text
  • Abstract: Science Direct Abstract
  • Other: Science Direct PDF
  • Journal Article Nguyen TH, Sabbah I, Ball WP. Sorption nonlinearity for organic contaminants with diesel soot: method development and isotherm interpretation. Environmental Science & Technology 2004;38(13):3595-3603.
    abstract available   full text available
    R828771C001 (2004)
    R828771C001 (2005)
    R828771C001 (Final)
  • Abstract from PubMed
  • Other: ACS Publications PDF
  • Journal Article Sabbah I, Ball WP, Young DF, Bouwer EJ. Misinterpretations in the modeling of contaminant desorption from environmental solids when equilibrium conditions are not fully understood. Environmental Engineering Science 2005;22(3):350-366.
    abstract available  
    R828771C001 (2004)
    R828771C001 (2005)
    R828771C001 (Final)
  • Abstract: Liebert Abstract
  • Other: Liebert PDF
  • Supplemental Keywords:

    contaminant mixtures, bioavailability, sorption, biodegradation, mass transfer, bioremediation, natural attenuation,, 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 assessment

    Relevant Websites:

    http://www.jhu.edu/hsrc Exit
    http://engineering.jhu.edu/~dogee/ball Exit
    http://engineering.jhu.edu/~dogee/bouwer Exit

    Progress and Final Reports:

    Original Abstract
  • 2002 Progress Report
  • 2003 Progress Report
  • 2004 Progress Report
  • 2006
  • 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