Overview of GMS

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Groundwater Research _at_ Department of Civil
Engineering Auburn University
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EWR Faculty Members

• Dr. Mark Barnett (Geochemistry)
• Dr. Don Zhang (Chemical treatment processes)
• Dr. Cliff Lange (Microcosm and soil microbiology)
• Dr. Willie Harper (Microbiology of wastewater)
• Dr. Prabhakar Clement (Groundwater)
• Dr. Joel Melville (Hydraulics)
• Dr. Melek Kazezyilmaz-Alhan (Hydrology)

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Understanding microbiology and chemistry of GW
systems
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Brooklawn Superfund site
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Microcosm work
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Biodegradation of mixed organics- PCE, TeCA, TCE
and TCA
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Nano-particle researchDr. Don Zhao
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Dechlorination using ZVI (nano-particles)

• Reduction of TCE
• Advantages
• High reactivity and fast kinetics
• No toxic intermediates

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Modifications of Fe(0) particles

• Coat iron with a metal catalyst such as Pd, Ni,
  Cu
• Reduce the particle size to nanoscale

Fe0 Pd2? Fe2 Pd0
4Fe3 3BH4- 9H2O? 4Fe0 3H2BO3- 12 H 6H2
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Preparation of Starch Stabilized Fe(0)
Nanoparticles
Add electron donor, BH4- and an IX resin
Add Fe3 or Fe2 (0.051 g/L as Fe)
Step 3. Formation of Fe(0) clusters coated with
stabilizers
Step 1. Solution with 01 (w/w) of a stabilizer.
Step 2. Fe3 or Fe2 complexes with stabilizer
Add a Secondary metal, Pd (0.1 of Fe)
Step 4. Formation of stabilized Fe-Pd bimetallic
nanoparticles.
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The Dispersibility of Nanoparticles in Soil
Non-stabilized Stabilized
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Dechlorination of TCE Using Various Fe-Pd
Nanoparticles
C0 50mg/L Fe 0.1g/L Starch or NaCMC 0.2
(w/w) PdFe 0.1/100
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Feasibility of reducing source zone flux by
injecting nano-particles
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TCE Flux Experiment with 1 ml 4 ml/min flow
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TCE Flux Experiments 1 ml TCE flush with 4
ml/min, 8 ml/min, 4 ml/min
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Geochemistry of metalsDr. Mark Barnett
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Remediation of Metals and Radionuclides

• Unlike organic contaminants, metals and
  radionuclides cannot be degraded

• However, metals and radionuclides undergo a
  variety of biotic and abiotic transformations

• Adsorption/ion exchange
• Precipitation/dissolution

• Oxidation/reduction
• Complexation

• Understanding these transformations crucial to
  successful site cleanup

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Determine the form of Hg in the Soil

• Using a combination of modeling, leaching tests,
  and x-ray/electron beams methods, determined that
  the Hg in the soils was predominantly HgS(s), a
  relatively insoluble, non-bioavailable Hg form

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Projects related to Metals

• Arsenic reactions with Mn02
• Uranium reactions with iron-coated sands
• Development of a geochemical package for RT3D
  coupled to surface-complexation sorption models
• Fate and transport of Hg in environmental systems
• Treatment methods for arsenic contamination
• Bioavailability of heavy metals

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Understanding contaminant transport
characteristics near salt wedge
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Experimental Setup
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Tank Details

• Dimensions of the flow tank
• 53 x 28 x 2.5 (cm)
• Saltwater density
• 1.04 g/ml
• Porous media Glass beads
• d50 1.1 (mm)
• Porosity 0.40
• K (hydraulic conductivity) 1200 m/day
• Stainless steel screen to minimize entry/exit
  losses

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Experiment Details

• Salt solution is made with water, NaCl and red
  dye (tracer)
• Density is measured periodically with a
  hydrometer to ensure consistency
• Constant head chambers were employed on both
  freshwater and saltwater sides to maintain steady
  head

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Sample Experimental Data A1 FW Head 29.3
cm SW Head 28.3 cmDensity of Saltwater 1.04
g/mL
?h 1 cm
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Steady State Data Set for Saltwater Density of
1.04 g/mL
?h 0.8 cm
?h 1 cm
?h 1.2 cm
?h 1.5 cm
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Contamination of coastal zones
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Saltwater intrusion
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Field sampling near a wedge.
Looking for problems!
High tech drilling!
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Field sampling (Salt conc.)
Figure from Sean Westbrook, MS work completed at
University of Western Australia CSIRO Perth
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Field sampling (Benzene conc.)
Figure from Sean Westbrook, MS work completed at
University of Western Australia CSIRO Perth
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Transport near a salt wedge (lab)
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Transport near a salt wedge
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Transport near a salt wedge
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Analytical solution to reactive transport (USEPA
tool BIOCHLOR/ ART3D)