Bioavailability Control and In-situ Stabilization of Contaminated

Sediments Using Carbon Sorbents

RTDF Sediments Remediation Action Team MeetingSeattle, Washington, October 29-30, 2002

Upal GhoshDepartment of Civil & Environmental Engineering,

Stanford University, Stanford, CA

From Nov 1:

Department of Civil & Environmental Engineering,

University of Maryland Baltimore County, Baltimore, MD

Sediment chemistry and bio-uptakeTraditional view

Sediment

Sed organic carbon

Benthic Organisms

Water

Fish

Higher animals

BSAF foc.Koc

Sediment chemistry and bio-uptake

What we see when we look closely

Sediment

soot

Benthic Organisms

Water

Fish

Higher animals

BSAFfor each sorbent

foc.Kocfor each sorbent

Natural organic matter

coal Oilgrease

pitchCokechar

wood

2

3

4

5

6

7

activ

ated c

arbon

soot

carbo

n

partic

ulate

coal

partic

ulate

charc

oal

heav

y fue

l oil

coal

tarPula

keroge

nco

llage

nhu

mic ac

id

degra

ded al

gae

amorp

hous

orga

nic m

atter

chan

nel se

dimen

t

Green R

iver k

erogen

oxidi

zed h

umic

acid

cutic

le

Mississ

ippi R

iver s

edim

ent

algae

Massa

chus

sets

Bay se

dimen

t

Woodb

urn so

il

soil o

rganic

matter

lignin

cellu

lose

log

Koc

Sediment-water partitioning of phenanthreneCs = Caq . Koc . foc

Need to identify sediment component(s) that have major influence on contaminant availability

Milwaukee Harbor Sediment

Likely sources of PAHs and coal: coking operations, gas manufacturing, harbor coal transportLandtreatment to reduce PAH concentrations in CDF sediment

Manufactured Gas OperationsUtica, NY circa 1935

Sediment sampling at Hunters Point

• PCB hot spot in San Francisco Bay• Samples collected from intertidal zone in south basin

Heavy mineral particles: sand (sd), silt, claysLight organic particles: coal (co), cenospheres (ce), charcoal (ch), pitch (pi),

wood (wd),

Light microscopy images of sediment particles(250-1000µm)

Petrography analysis of organic particles

Harbor Point, NY Milwaukee Harbor, WI Hunters Point, CA

Distribution of PCB/PAH in sediments

Three sites show 5-7% wt. lighter density carbonaceous matter (coal/charcoal/wood)

PCBs and PAHs associated with lighter density fraction (60-90%)

Lesson:Over time PCBs [and PAHs] preferentially accumulate in coal/charcoal/coke where they are strongly bound and less bioavailable

See:Ghosh et al., 2000, ES&T, 34, 1729-1736Ghosh et al., 2001, ES&T, 35, 3468-3475Talley et al., 2001, ES&T, 36, 477-483.

0

20

40

60

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100M

ilwau

kee

Harb

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I

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int,

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Hunt

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% s

edim

ent m

ass

Heavy Light

0

20

40

60

80

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Milw

auke

eHa

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, WI

(PAH

)

Harb

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AH)

Hunt

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(PAH

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AH o

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Heavy Light

Our experimental strategy: • PCB/PAH particle-scale measurements • PCB flux and aqueous equilibration• Mass transfer of PCB/PAH to sorbent and binding

energy• PCB bio-uptake:

• Three organisms: amphipod,worm, and clam• Two sorbents: coke and regenerated activated carbon• Variables: dose, contact time, particle size

• Sorbent type & PCB assimilation efficiency by clams• Organism survival, growth, reproduction, stress

Link chemistry and bio-uptake• Hypothesis: The

bioavailability of PCBs, PAHs, & DDT, depends on particle type to which they’re bound

• Can we change PCB bioavailability?

• New strategy for sediment management by in situ stabilization

Benthic organisms in Hunters Point sediment accumulate PCBs

Sediment-sorbent contact

• Sediment-sorbent contact experiments to assess effect of particle size, dose, and contact time on PCB availability

• Sorbent dose: 2x & 5x TOC

• Sorbent size: 100-250 µm & 63-100 µm

• Contact time: 1 month & 6 months

Bioaccumulation studies

Neanthes arenaceodentata

Leptocheirus plumulosus

• Survival, growth, reproduction, activity• PCB bioaccumulation

Macoma Balthica

PCB Bioaccumulation in Clams

0

400

800

1200

1600

2000

Tri Tetra Penta Hexa Hepta Octa Nona

PCB Homolog

PCB

Con

cent

ratio

n, n

g/g

dry

tissu

e UntreatedAc-Carbon Treated

Overall reduction in PCB bioaccumulation after 1 month contact with Ac. Carbon:Macoma: 69% Leptocheirus: 72%

Aqueous equilibrium tests

Measure PCB equilibrium concentrations for untreated and various sorbent-treated sediments:

•17 ppt seawater + sodium azide•contact 14 days on bottle roller•flocculate colloids with alum and centrifuge

3.4 wt% activated carbon: 86% reduction in aqueous PCBs

Alum-flocculation to remove colloids

(Ghosh et al., ES&T 2000)

Controlled particle feeding tests:assimilation efficiency

Depuration beakers

14C-PCB3H-PAH

Prepare labeledparticles

Feed clams

Depurate and analyze clam tissue and feces

Clam assimilation studies•Track 3H-BaP and 14C-2,2’,5,5’ PCB through a clam

•Feed 8 hours•Depurate 4 days•Analyze clam tissue and feces

FecesSiphons

Assimilation efficiency

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

PAH PCB

Activated CarbonCokePeatAnthraciteCharWood IWood IIDiatoms

Acknowledgements!

• DoD SERDP, Ford Fund, Schlumberger, Gas Technology Institute, USArmy Corps of Engineers, US Geological Survey

• Stanford Bio-X Initiative, Stanford Graduate Fellowship Program• US Army Waterways Experiment Station, Todd Bridges, Rod Milward

UMBC main LibraryEngineering Research Center, CEE dept.

University of Maryland Baltimore County

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