INNOVATIVE APPROACHES TO IN SITU ASSESSMENT AND REMEDIATION AT CONTAMINATED SEDIMENT SITES

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INNOVATIVE APPROACHES TO IN SITU ASSESSMENT AND
REMEDIATION AT CONTAMINATED SEDIMENT SITES

Louis J. Thibodeaux Jesse Coates Professor,
Gordon A. and Mary Cain Department of Chemical
engineering, Louisiana State University 70803
USA
Presentation at Pan-American Advanced Studies
Institute in Rio de Janeiro, Brazil. Sponsors
US Environmental Protection Agencies
Hazardous Substance Research Centers and the
National Science Foundation, USA
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The Challenge of Contaminated Sediment Beds

• ORIGIN-human activities effect rate and introduce
  contamination.
• SOURCES-runoff, urban and agricultural effluents,
  industrial and domestic waste point sources,
  atmospheric fall-out, accidents, etc.
• SINKS-stream, lake, estuary, and coastal marine
  beds.

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The Challenge continued

• Contaminants-organics, chlorinated organics,
  metals, pesticides, and conventional pollutants.
• Sites-Small area hot spots with very high levels
  and deep deposits near outfalls and other
  discharge points. Large surface areas with
  significant levels and shallow deposits.

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SOURCES OF CONTAMINATED SEDIMENTS
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Example Bayou Bonfouca Louisiana, USA

• Source-Creosote wood treating operation 1892 to
  1972.
• Sink-A freshwater stream and ideal sediment trap
  flow of 13cfs.
• Contaminants-Polyaromatic hydrocarbons including
  benzo(a)pyrene, naphthalene, and 14 others.
• Site dimensions- length 4300 ft by 125 ft wide
  and water average of 10 ft.
• Concentrations-Total PAHs 3,380 mg/kg and
  maximum13,450.

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CONTAMINATED SEDIMENTS-MULTIMEDIA ASPECTS FOR
EXPOSURE RISK

• The contaminated bed site PRIOR TO REMEDIATION.
  Both soluble and particle fractions move
  downstream. Volatilization to air occurs as
  well.
• DURING REMEDIATION additional releases occur
  The disturbed bed produces enhanced downstream
  chemical movement and volatilization. Dredged
  material handling at the excavation unit,
  transportation, residue treatment and final
  disposal generate releases.
• POST REMEDIATION activities result in releases.
  Losses occurs from the dredged material confined
  disposal facility in runoff, seepage and
  vaporization. In stream residues, both fall-back
  and non targeted material, drive low level
  releases.
• Excavation implied.

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CONTAMINANT RELEASE STAGES DURING REMEDIATION
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CHEMICAL FATE AND TRANSPORT ACROSS THE SEDIMENT
WATER INTERFACE
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Chemical Fate and Transport(CFaT) ProcessesThose
operative in the bed and the adjoining benthic
boundary layer.

• A brief review of all processes.
• Ranking processes to select the significant ones.
• Details of the particle processes and the
  soluble/bioturbation-coupled boundary processes.

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A BRIEF REVIEW OF ALL PROCESSES.
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process review continued.
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Definitions.
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definitions continued
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More definitions
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Mass-Transfer Coefficient Ranking

• _____________________________________
• Particle resuspension 0.2 to
  4.3
• Molecular diffusion
  0.00088
• Biodiffusion of particles 0.0052
  to .030
• Benthic boundary layer(waterside) 0.047 to .16
• Biodiff. Particles and BBL in series 0.0047 to
  .024
• --------------------------------------------------
  ---------------
• Based on MTC flux/Csp, in mm/day data from
• Fox River, WI.

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Storm Events and Their Duration
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Very recent findingsIt should not be presumed
that rare storm events cause catastrophic impacts
at the site under review.C. Kirk Ziegler,
2002.The soluble fraction chemical release
rates from contaminated bed sources to the
overlying water is more significant than once
thought.Louis J. Thibodeaux, 2002.
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Box Diagram of the Chemical Sub-module
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Mass sediment suspended from a cohesive bed
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Bed Density vs Depth
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Depth of Scour
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New Bedford Harbor Bed Sediment Concentration
Profile
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Feeding Types of Benthic Organisms
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Organism Densities with Depth into the Bed
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Chemical Transport Mechanisms-molecular diffusion.
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mechanisms continued-biodiffusion vs molecular.
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Advection Enhancement to Molecular Diffusion
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Chemical Transport-Particle Resuspension vs
Soluble ReleasePercent() Compared on a Flux
Basis.___________________________________________
______Stream Model
Particle Soluble______________
___________________________________Lower Fox, WI
Limno-Tech. 70
30Lower Fox, WI Wisconsin DNR
99 1Hudson, NY
Limno-Tech. 20-30 70-80 U.
Hudson, cohesive QEA
0 100U. Hudson, non-cohesive
QEA 4 96TIP,
Hudson, cohesive QEA
25 75 TIP, Hudson, non-cohesive
QEA 0 100
Grasse, NY QEA
37 63____________________
_______________________________Estimated by LJT
from published report.
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Illustration of Bioturbation Coupled to Benthic
Boundary Layer - Process of Soluble Release
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Mechanism for Soluble Release at Sites of Active
Bioturbation.____________________________________
_______________________1. Bioturbation of
particle-bound hydrophobic organic compoundsfrom
depth through the upper decimeter of the bed to
the interface,
2. Rapid chemical
desorption at the sediment-water interface
followed by3. Transport through the benthic
boundary layer to the water column.
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Bioturbation Model Algorithm
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Summary of In-Bed Processes