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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
80
100M
ilwau
kee
Harb
or, W
I
Harb
orPo
int,
NY
Hunt
ers
Poin
t, CA
% s
edim
ent m
ass
Heavy Light
0
20
40
60
80
100
Milw
auke
eHa
rbor
, WI
(PAH
)
Harb
orPo
int,
NY(P
AH)
Hunt
ers
Poin
t, CA
(PAH
)
Hunt
ers
Poin
t, CA
(PCB
)% P
AH o
r PCB
in fr
actio
n
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
• Founded in 1966• Newsweek’s top 12 Hot College list for 2003