Final Report: Desorption of Nonpolar Organic Pollutants from Historically Contaminated Sediments and Dredged Materials

EPA Grant Number: R825513C016
Subproject: this is subproject number 016 , 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: Desorption of Nonpolar Organic Pollutants from Historically Contaminated Sediments and Dredged Materials
Investigators: Tomson, Mason B. , Kan, Amy T.
Institution: Rice University
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1995 through January 1, 1998
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 , Land and Waste Management


The objectives of these studies were 1) to develop a semi-empirical equation to correlate the chemical types and irreversible compartment capacity; 2) to test the cause and effect relationship between the release of contaminants from historically contaminated sediments; and to examine the consequences of these results to sediment quality.

Summary/Accomplishments (Outputs/Outcomes):

Irreversible Compartment Capacity
Previous work indicated that the Lula sediment has a limited capacity in the irreversible compartment. Once the capacity of the irreversible compartment is satisfied, the additionally adsorbed compounds will adsorb and desorb reversibly. Cyclic adsorption/desorption studies are conducted to determine if similar phenomena can be demonstrated with different sediments and chemicals and to measure the maximum capacity of the irreversible compartment in several sediments. Two criteria are used to confirm that the irreversible compartment capacity is reached: 1) the additional adsorption will desorb reversibly; and 2) mass left on the solid is quantitatively extracted at the end of the over one hundred experimental steps.

Irreversible Adsorption Isotherm
Based upon experimental results, a conceptual biphasic irreversible adsorption model was proposed. This conceptual model is consistent with many laboratory and field observations, even though different mechanisms have been proposed (Pereira, et al., 1988, McGroddy, et al., 1995, Readman, et al., 1987, Carrol, et al., 1994, and Spencer, et al, 1996). All field observed concentrations are either equal to (within experimental error) or less than the laboratory predicted maximum concentration.

Desorption from Historically Contaminated Sediments
Extensive desorption studies were done with Lake Charles sediment and Utica sediment to test the desorption phenomena of chemicals in aged, and weathered sediments. Desorption was induced by both continuos extraction with a hydrophobic sorbent (Tenax), water and solvent extraction at different temperatures, pH, etc., and the effects of natural mixing. Experiments were also conducted to investigate the effects of chemicals which had been on the solid phase for years to the adsorption and desorption of freshly added chemicals and vice versa.

Irreversible Compartment Capacity
Several generalizations can be made from these data:

1) The adsorption values are predictable with the literature reported KOC/KOW relationships.

2) The solution phase concentrations () that equilibrate with the irreversible capacity remain at a constant concentration in the range of 0.6 to 27 g/l. This concentration is not a strong function of the chemical types nor of the solid phase concentration. Note that the aqueous solubility of these chemicals varied by 5.7 orders of magnitude and that the solid organic carbon content varied by a factor of 15. These observations show that the desorption from the irreversible compartment is not controlled by properties of the chemicals, but is a characteristic property of the solid phase. The kinetics of desorption from the irreversible compartment have not been thoroughly investigated, but preliminary studies have been done and will be reported later.

3) The solid phase irreversible capacity () is generally proportional to the organic carbon content. The organic carbon normalized capacity () ranges from 102.0 to 104.1 g/g-OC, while the KOW ranges from 102.65 to 106.36ml/g. It is noteworthy that the highest capacity () is not related to the most soluble nor to the most insoluble compounds, as one would commonly expect. Instead, the highest () is observed with compounds with intermediate solubility (naphthalene and dichlorobenzene, KOW103.4) and in high OC sediments (1.5 and 4.1% OC). Although these correlations appear promising, they must be regarded as preliminary, at this time and we are in the process of testing such ideas.

4) The desorption KOC from the irreversible compartment strongly deviates from the commonly reported KOC/KOW relationship. The desorption KOC from the irreversible compartment is about constant with the mean log value of 5.50.5. These data are constant with numerous literature reports of field observations that the KOC of the "refractory" phase is a constant or of lesser dependence on KOW instead of a linear function of KOW (Burgess, et al., 1989 and Baker, et al 1991). Our laboratory observations are consistent with those field observations. This observation might have significant impact on fate modeling, passive and active remediation, and regulatory activities. For example, the EPA proposed Sediment Quality Criteria (SQC) is based on an equilibrium model with conventional KOC/KOW relationships, which does not represent numerous field observations. This new insight to the relationship will provide the technical rationale to properly select the criteria to set sediment quality. Although these observations and correlation to appear to describe the maximum irreversible equilibrium, they do not explain the stepwise filling of the irreversible compartment.

Irreversible Adsorption Isotherm
Considering the observations mentioned in the Approach section and previous results published by the authors (Kan, et al., 1997, Kan, et al., 1994, Fu, et al., 1994, and Hunter, et al., 1996) a biphasic model of adsorption is proposed:

q( g/g of sediment) = qrev ( g/g of sediment) + qirr ( g/g of sediment) (1)

where q( g/g) represents the total concentration of adsorbed compound in the solid phase, qrev( g/g) represents the concentration of adsorbed compound in the solid phase that can participate in labile or reversible partitioning, and qirr ( g/g) represents the concentration of adsorbate that is sorbed in the second or irreversible, compartment. Sorption to the reversible compartment has been shown to be well represented by a commonly used linear isotherm qrev + KOC OC C. Since the qirr-portion has a well delineated maximum for each compound and sediment combination, a Langmuirian-type sorption isotherm is derived to represent this portion of the sorption. Substituting the linear and Langmuirian portions to Eq 1, the overall sorption can be represented by the following equation:
q = KOC OC C + (2)
where is the maximum capacity of the irreversible compartment and (ml/g) is analagous to KOC but for the irreversible compartment. f(0 f 1) is the fraction of the irreversible compartment that is filled at the time of exposure, and can be assumed equal to one when the exposure concentration is greater than about one half the aqueous solubility, which is probably the case in most point source contamination. The functional form of the second term on the right hand side of Eq 2 can be arranged to a more commonly expressed Langmuir isotherm {bQ C/(1+bC)}, by dividing the numerator and denominator by and setting and . When the aqueous concentration, C( g/ml), is relatively large, the second term reduces to a constant, . Similarly, when C is relatively small, the second term reduces to .

Desorption from Historically Contaminated Sediments
The desorption of these aged chemicals from Lake Charles sediments appears to be kinetically slow with a significant fraction of the solid phase chemicals resist desorption. Similar observations have been made with laboratory spiked samples and Utica sediment as reported in the PI's previous sediments papers . It is noteworthy that the solution phase concentration in in the magnitude of 1 g/l for four chemicals (two dichlorobenzenes, hexachlorobutadiene, and hexachlorobenzene), while the solid phase concentration varied by two orders of magnitude and the aqueous solubility of these chemicals varied by four orders of magnitude. The aqueous phase concentration of 1,2,4 trichlorobenzene is more than one and one half order of magnitude lower than that of the other four compounds. This may be the result of low 1,2,4 trichlorobenzene concentration in the solid phase. These observations are similar to the laboratory observations reported in the PI's papers, indicating that the "irreversible adsorption" phenomenon observed with the laboratory spiked samples are phenomenologically similar to the desorption from historically contaminated samples. Vigorous mixing by tumbling the sediment/water mixture at 2 rpm only increases slightly the extent of desorption as compared to gentle shaking of the sediment/water mixture during desorption. Increase the solution alkalinity to 1 M NaOH and increase sediment/water temperature to 100C only increases the desorption slightly in both the laboratory spiked and historically contaminated samples. The contaminated Utica sample and the laboratory spiked Lula sediments also resist solvent extraction to different degrees. In comparison, methylene chloride and acetone are better than hexane as extraction solvents, indicating that the difference may be due to the penetration of organic solvents to the solid organic phase. The solubility parameters of methylene chloride and acetone are similar to that of the soil organic phase and therefore, they may be able to swell the solid organic matter and release the entrapped organic chemical.

Summary of Results:

  • Discovered the phenomenon of irreversible sorption of hazardous chemicals in sediments
  • Described/proposed a mechanisms to explain the phenomenon of irreversible sorption
  • Developed a quantitative/predictive method to estimate "How Clean is Clean" in contaminated sediments
  • Helped to describe uncertainty in environmental risk assessment of contaminated sediments

  • Journal Articles on this Report : 5 Displayed | Download in RIS Format

    Other subproject views: All 32 publications 6 publications in selected types All 5 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 Hunter MA, Kan AT, Tomson MB. Development of a surrogate sediment to study the mechanisms responsible for adsorption/desorption hysteresis. Environmental Science & Technology 1996;30(7):2278-2285. R825513C016 (Final)
  • Full-text: ACS Full Text (PDF)
  • Journal Article Kan AT, Hunter MA, Fu G, Tomson MB. Effectiveness of chemically enhanced solubilization of hydrocarbons. SPE Production & Facilities 1997;12(3):153-158. R825513C015 (Final)
    R825513C016 (Final)
    R825465 (1998)
    R825465 (1999)
    R825465 (Final)
  • Abstract: SPE Abstract
  • Journal Article Kan AT, Fu G, Hunter M, Chen W, Ward CH, Tomson MB. Irreversible sorption of neutral hydrocarbons to sediments: experimental observations and model predictions. Environmental Science & Technology 1998;32(7):892-902. R825513C016 (Final)
    R822721C700 (1999)
  • Abstract: ACS
  • 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
  • Supplemental Keywords:

    adsorption, sediment quality, and risk assessment., RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Chemical Engineering, Contaminated Sediments, Environmental Chemistry, Fate & Transport, Analytical Chemistry, Hazardous Waste, Ecology and Ecosystems, Hazardous, Environmental Engineering, environmental technology, sediment treatment, hazardous waste management, hazardous waste treatment, risk assessment, fate and transport, contaminated marine sediment, soil and groundwater remediation, dredged material, biodegradation, contaminated sediment, kinetics, sediment resuspension, chemical contaminants, contaminated soil, marine sediments, remediation, chemical kinetics, hydrology, flume studies, currents, Lake Charles, extraction of metals, technology transfer, heavy metals, aquifer fate and treatment, technical outreach

    Progress and Final Reports:

    Original Abstract
  • 1995
  • 1996

  • 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