Final Report: Bioavailability of Desorption Resistant Hydrocarbons in Sediment-Water Systems.

EPA Grant Number: R825513C024
Subproject: this is subproject number 024 , established and managed by the Center Director under grant R825513
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (1989) - South and Southwest HSRC
Center Director: Reible, Danny D.
Title: Bioavailability of Desorption Resistant Hydrocarbons in Sediment-Water Systems.
Investigators: Hughes, Joseph B , Fleeger, J. W. , Kan, Amy T. , Pardue, J. , Reible, Danny D. , Thibodeaux, Louis J. , Tomson, Mason B. , Valsaraj, Kalliat T.
Institution: Georgia Institute of Technology , Louisiana State University - Baton Rouge
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1998 through January 1, 2001
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text |  Recipients Lists
Research Category: Hazardous Substance Research Centers , Nanotechnology , Land and Waste Management


The goal of this research is to characterize the irreversible desorption of hydrophobic organic contaminants to sediments and couple with the assessment of bioavailability to bioturbating macroflora, microorganisms, and aquatic plants. The specific objectives of the project included:

  • Determine the extent of irreversible adsorption to historically contaminated and laboratory prepared sediments and the effect of process variables such as T, pH, TDS, OC, flow and weathering on that adsorption.
  • Determine the impact of irreversible (or desorption-resistant) adsorption versus reversible adsorption on the biodegradation of organic contaminants and the corresponding interaction with bioturbation, and;
  • Determine the extent of organic contaminant bioaccumulation and metabolism by sediment-dwelling worms when ingesting contaminants that are adsorbed either reversibly or irreversibly;
  • Determine the rate, extent and effects of uptake of irreversibly sorbed contaminants on selected wetland plant systems and the associated rhizosphere.
  • Summary/Accomplishments (Outputs/Outcomes):

    The research is directed toward understanding and explaining the observed increased persistence and decreased availability of hydrocarbons in natural biologically-active sediments and the corresponding consequences to prediction, control and regulation of these contaminants. The are addressing three critical aspects of the bioavailability of the irreversibly adsorbed compartment: availability to microbial degradation, availability to bioturbating, sediment-dwelling macro fauna, and availability to wetland plant systems. These organisms and processes are generally the most significant influences on the fate of hydrophobic contaminants in sediments not subject to significant scour or resuspension. These studies have focused on low solubility organic contaminants with particular emphasis on polynuclear aromatic hydrocarbons (PAHs), which are known to be biodegraded and bioaccumulated and are primary soil and sediment contaminants in Regions 4 and 6.

    The conceptual model through which the work has been designed and interpreted is that defined by Mason Tomson, Amy Kan and co-workers at Rice University in research supported from 1991-1998 by the HSRC. This work has established that contaminant sorption to sediments is biphasic with a desorption-resistant fraction of fixed maximum capacity. The desorption from both reversible and the desorption-resistant compartments can be described by equilibrium considerations. The desorption isotherm observed by Tomson and Kan can be described by the combination of a linear and a nonlinear Langmuir isotherm. This approach is functionally equivalent to the dual reactive domain model of Huang and Weber (1997). The Rice research group has made substantial progress in establishing the concept of irreversible adsorption as a fate mechanism in natural sediments (e.g. Kan et al., 1994; Hunter et al., 1996; Kan et al., 1997; Kan et al. 1998).

    The evaluation of the characteristics and implications of the desorption-resistant contaminant fraction has progressed on two parallel paths:
    1. Continued investigation of the mechanisms and characteristics of the irreversible or aged fraction of contaminants in sediments led by Mason Tomson.
    2. Bioavailability studies on sediments with partially or fully desorbed reversible fractions (ie.e containing only desorption -resistant contaminants). These experiments were conducted by each of the investigators on microbial, plant or benthic organisms as appropriate.

    The work has focused on sediment from Bayou Manchac, Louisiana and the contaminant phenanthrene. Other sediments and contaminants were employed in some studies based upon availability, characteristics and performance in the various biological systems, and to contrast with phenanthrene behavior that will be determined subsequently. A summary of progress in each of the efforts identified above is included below.

    Desorption-resistant Fraction Characterization Studies
    The effects of competitive sorption, isopropanol extraction and tetrachlorethane reactivity were evaluated. The model of the irreversible sorption/desorption behavior was further tested and its ability to predict behavior of systems containing high hydrocarbon concentrations evaluated. The key results of work over the past year can be summarized as follows:
    1. The use of isopropanol as a rapid desorption extraction solvent was demonstrated and used to prepare large amounts of sediment for bioavailability studies. Use of aqueous solutions of 50% isopropanol gave desorption isotherm results essentially identical to multiple stepwise water desorptions. Results after a single extraction step with isopropanol, however, sometimes deviated from the isotherm due to reversible sorption during solvent exchange between the isopropanol solution and wash water.
    2. No competitive sorption or desorption effects were noted in tests with naphthalene alone, naphthalene with dichlorbenzene, and naphthalene with phenanthrene and pyrene.
    3. Reaction experiments with 1,1,2,2 tetrachloroethane showed rapid dehalogenation in the aqueous phase as well as significant rates of reaction on the solid phase in both activated carbon and in sediments with reversibly sorbed material. Essentially no surface reaction was noted, however, for desorption-resistant contaminants. This suggested that the physical nature of the compartment was such that surface reactions were hindered.

    The model of Kan and Tomson was able to accurately predict a variety of desorption isotherms of contaminants in sediments once the irreversible sorption capacity of a sediment is measured. Significant deviations were noted, however, in sediments with high total petroleum hydrocarbons suggesting its presence as a separate competing sorbent phase.

    To complete the work initiated to date, it is recommended that this component of the effort focus on development of an experimental protocol for the routine measurement of the capacity of the desorption-resistant compartment (to allow predictive isotherm modeling). This would also entail continued field testing of the experimental protocol and comparison to observations. There also remain significant mechanistic questions that may be resolved through collaborative analysis of the desorption-resistance with techniques and approaches devised by other groups, notably those of Dick Luthy at Stanford and Walt Weber at the University of Michigan. Both of these groups have noted similar behavior but ascribe to different mechanisms and employ different analytical tools. Use of common analytical tools can help identify if the same or different mechanisms are operative.

    Bioavailability of Desorption-resistant PAHs to Microbial Systems
    Sediments contaminated with only desorption-resistant naphthalene, phenanthrene and fluoranthene were prepared using a step-desorption procedure developed in Dr. Tomson's lab then inoculated with PAH-degrading microbial cultures from Dr. Hughes' lab to assess the ability of the organisms to sustain degradation at low aqueous phase contaminant concentrations. CO2 production was noted in all cultures despite the desorption-resistant nature of the contaminants. Further studies were conducted to determine if microbes produce extracellular materials that influence desorption resistance and to compare degradation rates to abiotic mass transfer release rates. Note that the model of desorption-resistance provides an equilibrium limit to the concentrations that can be obtained in the adjacent porewater. If either biological or physicochemical processes exist that remove the contaminant from the porewater, desorption toward this equilibrium will continue to occur.

    In the studies exploring the potential release of extracellular materials to enhance release, no measurable effects were noted on surface tension, PAH solubilty or the partition coefficient between the sediment and water. Abiotic desorption rates were estimated by the addition of a tenax adsorbent in the adjacent water. The observed desorption rates were faster than the biodegradation rates in all cases except for naphthalene degradation in the presence of high biomass concentrations. In all other cases, the degradation of the PAH compounds in the adjacent water was the rate limiting step of the combined desorption-degradation process. This again suggested that the observed degradation rates were not the result of desorption rate enhancements by the microbes.

    Bioavailability of Desorption-resistant PAHs to Wetland Plants
    Plant Uptake Study
    Laboratory studies conducted during this period indicate that wetland plants can access the desorption-resistant fraction of contaminants and enhance their removal from sediments. The bioavailability is less than observed in plants grown hydroponically or with freshly added contaminants, but is measurable. We hypothesize that two main mechanisms are important for plant uptake:
    Simple partitioning from the desorption-resistant fraction onto the external root surfaces leading to accumulation into the root.
    Translocation of the compound from the root to the vascular system of the plant. Translocation from the root to the upper stem seems to be directly proportional to water uptake. A mathematical model for uptake from sediments which considers the desorption-resistant fraction produces similar results to those obtained in the laboratory.

    Sorption and Desorption in Highly-Organic Sediments
    In addition to plant-uptake, we are interested in how the desorption-resistance phenomena operates in the highly organic detritus or peat soils with very recent organic matter. The Biphasic sorption model, slow sorption model, and dual-mode sorption model which consider different mechanistic explanations for the desorption-resistant fraction, have been used to fit sorption/desorption data from wetland soils. All models fit the data well. The results of the models consistently indicate that a desorption-resistance exists in highly organic wetland soils and that aging of the organic matter increases the size of that fraction. Desorption-resistance and the observation of increased desorption-resistance with increasing organic matter age should be considered in remediation efforts and may explain why some remediation technologies will not achieve desired results. Specific results for each model include:
    Biphasic sorption model: Chemical concentration in the maximum capacity of the desorption-resistant compartment, qirrmax , of the deeper soil was greater than surface soil for both CB and Phenanthrene. Desorption-resistant or sequestered fraction exists for highly organic wetland soils. A significant fraction of contaminants would be partitioned into the desorption-resistant fraction in wetland soils. Qirrmax (OC) of the PPI and BM soils were greater than wetlands soils. The Kirroc value increased in order of surface surface < deeper << PPI < BM indicating that desorption-resistance increases with soil age.
    Dual reactive domain model (DRDM): The organic matter normalized partition coefficient for linear fraction, KD,LOC of the deeper soil was consistently higher than surface soil. For both CB and Phen, the Langmuir site energy factor, b and the Langmuir capacity factor, Q0 were higher in deeper soil and subsequently Q0b representing the Langmuir sorption capacity of the nonlinear sorption was greater in deeper soil. CB has two-regional behavior: when Ce << 1, qe, NL = Q0b Ce and when Ce >> 1, qe, NL = Q0. In contrast, Phen has only one-regional behavior: qe, NL = Q0b Ce since b is much smaller than 1 (b << 1). The higher Q0b value of the deeper (older) soil indicates that nonlinear sorption fraction in the soil increases with soil age. Comparison of nonlinear fraction of DRDM (qe,NL) and desorption-resistant fraction (qirrmax) of biphasic sorption model shows that both model predicts desorption-resistant phase similarly.
    Slow sorption model: KF,OC values of the deeper soil were significantly greater than surface soil for both fast and slow sorption phase. Both fast and slow sorption capacities of older soil were greater than younger soil in order of BM > PPI >> deeper > surface soil. Differences in sorption capacities with soil age were well explained by soil elemental ratios; higher H/C and O/C ratios indicate "older" organic matter. The increase of the slow sorption fraction with soil age is further evidence that desorption-resistance is observed in wetland soils.

    Bioavailability of Desporption-resistant PAHs to Benthic Organisms
    Assessments of the bioavailability of the desorption-resistant or sequestered fraction to several tubificid oligochaetes have been made. The BSAF is the quantity of contaminant accumulated in the organism after a period of exposure normalized by the organisms lipid content and the organic carbon normalized sediment loading of the contaminant.
    BSAF~=~ {q_organism `/ `f_lipid} over {q_sediment`/`f_oc}

    Deposit-feeding oligochaetes process large amounts of sediment directly leading to high exposures to whatever fraction of the sediment contaminant is available. As long as the rate of uptake of the contaminant is large compared to metabolic or other fate processes within the organism, this generally means that the BSAF approaches unity since the lipid sorption potential is similar to the sorption potential of the organic carbon in the sediments. For fully reversibly-sorbed PAHs, we have noted BSAF ~1 in deposit feeding oligochaetes within 2-5 days for phenanthrene and within 7 days for pyrene. Ankley et al. (1992) demonstrated BSAFs ~ 1 for both laboratory and field oligochaetes exposed to a wide variety of PCB congeners in Fox River/Green Bay sediments.

    Deviations from unity would be expected when the effective partition coefficient between the sediment and water (or gut juices of the worm) is different from the partition coefficient between the lipid and water (or, again, gut juices). The model of Tomson and Kan suggests that the sequestered fraction exhibits a higher sediment-water partition coefficient than is predicted by reversible partitioning rules. Since the partitioning to the lipids would not be affected by desorption resistance in the sediment, the BSAF should decrease in inverse proportion to the increase in the sediment-water partition coefficient. Using this simple inverse linear model, Table 1 includes a variety of predicted and observed BSAF values from both the current experiments and the literature. Using both literature sources and these experiments, the inverse linear model predicts the observed BSAFs with a correlation coefficient of 0.92. The conclusion to be drawn is that the decreased desorption equilibrium directly affects the potential for bioaccumulation in organisms.

    The rate at which this modified equilibrium is reached, however, is not well understood. Measurements of BSAFs after only 5 days appear to be at equilibrium while the experiments conducted with tenax adsorbent in a sediment-water slurry suggest that 10 days is required to desorb 10% of the phenanthrene mass from the sediments. Single gut passage assimilation efficiency experiments are needed to directly compare rapid assimilation of reversibly sorbed contaminants (single gut passage assimilation efficiencies of 40-50%) to the assimilation rate of the desorption resistant fraction. Conduct of these experiments will require radiolabeled contaminant levels that significantly exceed those used to date due to the relatively small mass of uptake expected in the single gut passage experiments. The "hot" sediment to be employed in these experiments also allows us to address the question as to whether the bioavailability of the contaminants are different after ingestion and processing by the worm. There will be sufficient material in the fecal matter generated to allow microbial degradation experiments to be performed on the processed material. Both of these efforts will be the subject of the work to be performed to conclude the experimental program.

    Table 1 - Comparison of observed contaminant accumulation in various benthic worms and that predicted by effective partitioning between sediment and water
    Contaminant - dominant state Concentration mg/kg Ksw|eff BSAF Predicted BSAF2
    Pyrene - reversibly sorbed 1 <50 750 1.01?0.45 1
    Pyrene - supersaturated sediments 1 127 980 0.7?0.1 0.77
    Pyrene - supersaturated sediments 1 240 1850 0.4?0.05 0.47
    Fluoranthene - with adsorbent resin 3 97 38,250 0.0139?0.01 0.019
    Phenanthrene - reversibly sorbed 4 85 mg/kg 260 1.20?0.44 1
    Phenanthrene mostly reversibly sorbed 4 32 mg/kg 350 1.19?0.23 0.75
    Phenanthrene - mostly sequestered rapid isopropanol washes 4 8 mg/kg 760 0.60?0.16 0.34
    Phenanthrene - mostly sequestered w/XAD in sediment 4 14 mg/kg - 0.245?0.004 -


      1. Pyrene experiments conducted with Limnodrilus hoffmeisteri
      2. Effective BSAF is equal to ratio of Kd|eff to tabulated value or value observed with reversible contaminants
      3. Kasian et al. (1999) with Lumbriculus variegatus
      4. Phenanthrene experiments conducted with Illodrillus templetoni

    Journal Articles on this Report : 9 Displayed | Download in RIS Format

    Other subproject views: All 44 publications 18 publications in selected types All 9 journal articles
    Other center views: All 392 publications 154 publications in selected types All 106 journal articles
    Type Citation Sub Project Document Sources
    Journal Article Chen W, Kan AT, Fu G, Vignona LC, Tomson MB. Adsorption-desorption behaviors of hydrophobic organic compounds in sediments of Lake Charles, Louisiana, USA. Environmental Toxicology and Chemistry 1999;18(8):1610-1616. R825513C016 (Final)
    R825513C024 (Final)
    R822721C700 (1999)
    R828598 (Final)
    R828598C700 (Final)
  • Abstract: Wiley
  • Journal Article Chen W, Kan AT, Tomson MB. Irreversible adsorption of chlorinated benzenes to natural sediments: implications for sediment quality criteria. Environmental Science & Technology 2000;34(3):385-392. R825513C024 (Final)
    R822721C700 (1999)
    R826694C700 (1999)
    R826694C700 (Final)
    R828598 (Final)
    R828598C700 (Final)
  • Abstract: ACS
  • Journal Article Chen W, Lakshmanan K, Kan AT, Tomson MB. A program for evaluating dual-equilibrium desorption effects on remediation. Ground Water 2004;42(4):620-624. R825513C023 (Final)
    R825513C024 (Final)
    R828773 (2004)
    R828773 (Final)
    R828773C004 (2004)
    R831718 (2005)
    R831718 (Final)
  • Abstract from PubMed
  • Full-text: NationalGroundWaterAssociation-Full Text PDF
  • Abstract: Wiley-Abstract
  • Journal Article Kan AT, Chen W, Tomson MB. Desorption kinetics of neutral hydrophobic organic compounds from field-contaminated sediment. Environmental Pollution 2000;108(1):81-89. R825513C024 (Final)
    R822721C700 (1999)
    R826694C700 (1999)
    R826694C700 (Final)
    R828598 (Final)
    R828598C700 (Final)
  • Abstract from PubMed
  • Full-text: Science Direct-Full Text HTML
  • Abstract: Science Direct-Abstract
  • Other: Science Direct-Full Text PDF
  • Journal Article Kim S, Sioutas C, Chang M-C, Gong Jr. H. Factors affecting the stability of the performance of ambient fine-particle concentrators. Inhalation Toxicology 2000;12(Suppl 4):281-298. R825513C024 (Final)
    R826708 (2000)
    R826708 (2001)
    R826708 (2002)
    R826708 (Final)
    R827352 (2004)
    R827352 (Final)
    R827352C012 (Final)
    R827352C014 (Final)
    R828598 (Final)
    R828598C700 (Final)
  • Abstract from PubMed
  • Abstract: Taylor and Francis-Abstract
  • Journal Article Millward RN, Fleeger JW, Reible DD, Keteles KA, Cunningham BP, Zhang L. Pyrene bioaccumulation, effects of pyrene exposure on particle-size selection, and fecal pyrene content in the oligochaete Limnodrilus hoffmeisteri (Tubificidae, Oligochaeta). Environmental Toxicology and Chemistry 2001;20(6):1359-1366. R825513C024 (Final)
  • Abstract from PubMed
  • Abstract: SETAC Abstract
  • Journal Article Tomson MB. Causes and effects of resistant sorption in natural particles. Environmental Toxicology and Chemistry 1999;18(8):1609. R825513C016 (Final)
    R825513C024 (Final)
    R822721C700 (1999)
    R828598 (Final)
    R828598C700 (Final)
  • Abstract: Wiley
  • Journal Article Xiao JJ, Kan AT, Tomson MB. Prediction of BaSO4 precipitation in the presence and absence of a polymeric inhibitor: Phosphino-polycarboxylic acid. Langmuir 2001;17(15):4668-4673. R825513C024 (Final)
    not available
    Journal Article Xiao J, Kan AT, Tomson MB. Acid-base and metal complexation chemistry of phosphino-polycarboxylic acid under high ionic strength and high temperature. Langmuir 2001;17(15):4661-4667. R825513C024 (Final)
    not available

    Supplemental Keywords:

    bioturbation, phytoremediation, and bioremediation., RFA, Scientific Discipline, Waste, Water, Chemical Engineering, Contaminated Sediments, Environmental Chemistry, Analytical Chemistry, Hazardous Waste, Bioremediation, Ecology and Ecosystems, Hazardous, Environmental Engineering, environmental technology, sediment treatment, hazardous waste management, hazardous waste treatment, risk assessment, decontamination of soil and water, soil and groundwater remediation, microbial degradation, biodegradation, decontamination of soil, bioavailability, risk management, contaminated sediment, chemical contaminants, PAH, microbes, contaminated soil, bioremediation of soils, contaminants in soil, remediation, biotransformation, anaerobic biotransformation, waste mixtures, technology transfer, extraction of metals, bioturbation, phytoremediation, contaminated soils

    Progress and Final Reports:

    Original Abstract
  • 1998
  • 1999

  • Main Center Abstract and Reports:

    R825513    HSRC (1989) - South and Southwest HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825513C001 Sediment Resuspension and Contaminant Transport in an Estuary.
    R825513C002 Contaminant Transport Across Cohesive Sediment Interfaces.
    R825513C003 Mobilization and Fate of Inorganic Contaminant due to Resuspension of Cohesive Sediment.
    R825513C004 Source Identification, Transformation, and Transport Processes of N-, O- and S- Containing Organic Chemicals in Wetland and Upland Sediments.
    R825513C005 Mobility and Transport of Radium from Sediment and Waste Pits.
    R825513C006 Anaerobic Biodegradation of 2,4,6-Trinitrotoluene and Other Nitroaromatic Compounds by Clostridium Acetobutylicum.
    R825513C007 Investigation on the Fate and Biotransformation of Hexachlorobutadiene and Chlorobenzenes in a Sediment-Water Estuarine System
    R825513C008 An Investigation of Chemical Transport from Contaminated Sediments through Porous Containment Structures
    R825513C009 Evaluation of Placement and Effectiveness of Sediment Caps
    R825513C010 Coupled Biological and Physicochemical Bed-Sediment Processes
    R825513C011 Pollutant Fluxes to Aquatic Systems via Coupled Biological and Physicochemical Bed-Sediment Processes
    R825513C012 Controls on Metals Partitioning in Contaminated Sediments
    R825513C013 Phytoremediation of TNT Contaminated Soil and Groundwaters
    R825513C014 Sediment-Based Remediation of Hazardous Substances at a Contaminated Military Base
    R825513C015 Effect of Natural Dynamic Changes on Pollutant-Sediment Interaction
    R825513C016 Desorption of Nonpolar Organic Pollutants from Historically Contaminated Sediments and Dredged Materials
    R825513C017 Modeling Air Emissions of Organic Compounds from Contaminated Sediments and Dredged Materials title change in last year to "Long-term Release of Pollutants from Contaminated Sediment Dredged Material"
    R825513C018 Development of an Integrated Optic Interferometer for In-Situ Monitoring of Volatile Hydrocarbons
    R825513C019 Bioremediation of Contaminated Sediments and Dredged Material
    R825513C020 Bioremediation of Sediments Contaminated with Polyaromatic Hydrocarbons
    R825513C021 Role of Particles in Mobilizing Hazardous Chemicals in Urban Runoff
    R825513C022 Particle Transport and Deposit Morphology at the Sediment/Water Interface
    R825513C023 Uptake of Metal Ions from Aqueous Solutions by Sediments
    R825513C024 Bioavailability of Desorption Resistant Hydrocarbons in Sediment-Water Systems.
    R825513C025 Interactive Roles of Microbial and Spartina Populations in Mercury Methylation Processes in Bioremediation of Contaminated Sediments in Salt-Marsh Systems
    R825513C026 Evaluation of Physical-Chemical Methods for Rapid Assessment of the Bioavailability of Moderately Polar Compounds in Sediments
    R825513C027 Freshwater Bioturbators in Riverine Sediments as Enhancers of Contaminant Release
    R825513C028 Characterization of Laguna Madre Contaminated Sediments.
    R825513C029 The Role of Competitive Adsorption of Suspended Sediments in Determining Partitioning and Colloidal Stability.
    R825513C030 Remediation of TNT-Contaminated Soil by Cyanobacterial Mat.
    R825513C031 Experimental and Detailed Mathematical Modeling of Diffusion of Contaminants in Fluids
    R825513C033 Application of Biotechnology in Bioremediation of Contaminated Sediments
    R825513C034 Characterization of PAH's Degrading Bacteria in Coastal Sediments
    R825513C035 Dynamic Aspects of Metal Speciation in the Miami River Sediments in Relation to Particle Size Distribution of Chemical Heterogeneity