Phytoextraction of PCBs: Phytoextraction of PCBs: A Case StudyA Case Study
Ken Reimer *, Melissa Whitfield, Barbara Zeeb, and Allison Rutter
The PCB ProblemThe PCB Problem
• Used in adhesives, flame retardants, paints, dielectric fluids for transformers and capacitors etc
• Persistent in environment• Hydrophobic• Numerous PCB contaminated
sites remain in Canada and internationally
209 possible congeners depending on chlorine substitution
PCB Storage in CanadaPCB Storage in Canada
• Total of 1861 PCB waste storage sites in Canada (82 331 tonnes soil with >50ppm)
• Thousands more sites with PCBs <50ppm– Need for cost-effective remediation to improve property
values
0
100200
300400
500
<100 kg
100 kg - <
1
1 - <10
10 - <100
100 - <
1000
1000 - <
10000
>10000
size categories (tonnes)
# Si
tes
Federal
Non-Federal
Dec 2002
Current Methods of RemediationCurrent Methods of Remediation
Physical treatments• On-site extraction by
surfactants or solvents• On-site dechlorination (uses
high temperatures and basic conditions)
• On/off-site incineration
Alternatives• Bioremediation (using bacteria)• Phytoremediation (using
plants)Figure 2: PCB incinerator in St. Ambroise, QC (Kroeker, 2001)
PhytoextractionPhytoextraction
• Previously thought that hydrophobic organochlorines (log Kow >5) could not be extracted
• Now known that this is possible for compounds like DDT, PCBs
Schneider ElectricSchneider Electric
• World leader in electrical distribution, industrial control and automation products, systems and services
•Company acquired a PCB contaminated site in Etobicoke, Ontario, Canada
•Site is a Provincially registered & managed PCB Storage Facility
•Agreed to participate in a study of PCB phytoremediation
Objectives & TimelineObjectives & Timeline
1. To determine the efficacy of using phytoremediation as a strategy for remediating PCB-contaminated soil at the Schneider Electric site, and
2. To improve the marketability (through better knowledge of cost & regulatory factors) for using this technology in Canada.
trans
port 6
barre
ls so
il to R
MC
soil c
harac
teriza
tion
green
hous
e trea
tability
stud
ies
pilot-
scale
field
study
at R
MC
optim
izatio
n stud
ies w
ith su
rfacta
nts
field
study
at Sch
neide
r site
analy
sis of
field
study
sample
s
field
study
at Sch
neide
r site
O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D2002 2003 2004 2005
To examine potential for PCB phytoextraction
Parafilm seal between shoots & soils to eliminate direct contact pathways
Controlled GH StudiesControlled GH Studies
0
100
200
300
400
C. pepo var.Howden
(Pumpkin)
F. arundinacea(Tall Fescue)
C. pepo var.Goldrush(Squash)
PCB
s (u
g)ShootRoot
Greenhouse ResultsGreenhouse Results
0
200
400
600
800
1000
C. pepo var.Howden
(Pumpkin)
F. arundinacea(Tall Fescue)
C. pepo var.Goldrush(Squash)
[PC
B] (
ug/g
) ShootRoot
PCB-Concentration(ug/g)
vs.
PCB-Extraction(ug)
Homologue DistributionsHomologue Distributions
05
101520253035404550
tri tetra penta hexa hepta octa nona
% C
ontr
ibut
ion pure A1260
s oil
roots
s hoots
ExEx--Situ Field PlotsSitu Field Plots
Scaled-up,outdoorexperiments-same soil as greenhouse work
Safety considerations: – Registered PCB storage
facility– Water collection and
treatment– Spill barrier– Weekly air monitoring
Species used:– Pumpkin, Squash, Tall
Fescue, and Sedge
Greenhouse vs. Ex situ Field Greenhouse vs. Ex situ Field ResultsResults
[PCB]soil = ~500 ug/g
0
2000
4000
6000
8000
10000
GH Exsitu
GH Exsitu
GH Exsitu
GH Exsitu
PCB
s ex
trac
ted
(ug)
ShootRoot
C. normalis (Sedge)
n/a
C. pepo var Howden (Pumpkin)
C. pepo var Goldrush
(Squash)
F. arundinacea (Tall Fescue)
PCB-Extraction(ug)
ShootsShootsEx Situ Field vs. GreenhouseEx Situ Field vs. Greenhouse
T. Fescue Shoot
-2.0
-1.0
0.0
1.0
2.0
3.0
5/824/27
20/21 /33 46
41/64 /68/71+7256/60 91
83/10 7 82126147141
128+162 179183
172/1 92 197208
tri pentatetra hexa hepta octa nona
Enrichment of lower chlorinated congeners in ex situ field setting
Control plot (uncontaminated)(5 m x 5 m)
PCB contaminated plot (25 m x 7 m)
In situ In situ Field Trial: July 22 Field Trial: July 22 –– Oct 4, 2004Oct 4, 2004
Location of PCB Plots
Location of Control Plot
Horner Ave
Control Plot (Clean Soil)“Plot C”
XX
5 m
5 m
X
X XX
Contaminated Soil Plots
“Plots P1, P2, P3”
P1
P2
P3
X XX
X XX
Unplanted Control
25 m
7 m
Warehouse
Water Treatment
Experimental DesignExperimental DesignX - Mound of 4-5 Cucurbita pepo
cv. Howden plants- 0.5 m x 0.5 m plot of Festucaarundinacea
- 0.5 m x 0.5 m plot of Carexnormalis
August 11August 11
Tall Fescue
Sedge
Pumpkin
September 17September 17
Tall FescueSedge
Pumpkin
Harvesting, October 4Harvesting, October 4
Tall Fescue
Sedge
ResultsResults
Monitoring ResultsMonitoring Results
PCBs in air • All air samples taken at the site throughout the duration of the
field trial returned non-detect levels of PCBs in air (i.e. <2800mg/m3)
PCBs in groundwater • Groundwater passing through the field trial site was collected
and treated on-site. • Monthly testing of the discharge water revealed no changes
in [PCB]. Water continued to meet safe discharge levels.
Greenhouse vs. Ex situ Field Greenhouse vs. Ex situ Field vs. In situ Fieldvs. In situ Field
16 226 10 619
350
90
50
100
150
200
250
300
350
400
Sedge Pumpkin Tall Fescue
Shoo
t Len
gth
(cm
)
GreenhouseEx SituIn Situ
n/a
1260120 – 390 ug/g, median 170 ug/gGreenhouse
1254/12602 – 210 ug/g, median 30 ug/gIn situ
1260410 – 570 ug/g, median 520 ug/gEx situ
AroclorSoil [PCB]
4
305
386
24149
1098
271
0
200
400
600
800
1000
1200
Sedge Pumpkin Tall Fescue
Fres
h w
eigh
t of s
hoot
s (g
)
GreenhouseEx SituIn Situ
n/a
Greenhouse vs. Ex situ Field Greenhouse vs. Ex situ Field vs. In situ Fieldvs. In situ Field
05000
100001500020000250003000035000
GH Exsitu
Insitu
GH Exsitu
Insitu
GH Exsitu
Insitu
PCB
s ex
trac
ted
(ug) Shoot
Root
Sedge Pumpkin Tall Fescue
n/a
PCB-Extraction(ug)
• Increased biomass in situ resulted in large increases in total PCB uptake
PCB Distribution in PumpkinsPCB Distribution in Pumpkins
PCB Concentration in pumpkin P3 HPb1
0
5
10
15
20
0 100 200 300 400 500Distance from root (cm)
[PC
B] (
ug/g
)
Main StemLeavesLeaf Stems
•Similar PCB concentrations found in various tissues•Pumpkins themselves had the lowest concentrations – mainly found on the exterior surface•Distance from root was the most important factor influencing PCB concentration
0
100
200
300400
500
600700
800
5/824/2
720/2
1/3352/7
3 3770/7
656/6
083/1
09 136135
/144143
/134 153 141 129182
/187 177172
/192 169 189 205
0
100
200
300400
500
600700
800
5/824/2
720/2
1/3352/7
3 3770/7
656/6
083/1
09 136135
/144143
/134 153 141 129182
/187 177172
/192 169 189 205
0
100
200
300400
500
600700
800
5/824/2
720/2
1/3352/7
3 3770/7
656/6
083/1
09 136135
/144143
/134 153 141 129182
/187 177172
/192 169 189 205
congeners
006-008 cm
120-140 cm
440-472 cm
[PC
Bs]
ng/
g
C93/95 C105/127sum of congeners = 1 043 ng/g
sum of congeners = 7 723 ng/g
sum of congeners= 10 877 ng/g
di tri tetra penta hexa hepta octa nona
0.02.04.06.08.0
10.012.014.016.018.020.0
5/824/2
720/2
1/3352/7
3 3770/7
656/6
083/1
09 136135
/144143
/134 153 141 129182
/187 177172
/192 169 189 205
0.02.04.06.08.0
10.012.014.016.018.020.0
5/824/2
720/2
1/3352/7
3 3770/7
656/6
083/1
09 136135
/144143
/134 153 141 129182
/187 177172
/192 169 189 205
0.02.04.06.08.0
10.012.014.016.018.020.0
5/824/2
720/2
1/3352/7
3 3770/7
656/6
083/1
09 136135
/144143
/134 153 141 129182
/187 177172
/192 169 189 205
congeners
rela
tive
cont
ribut
ion
of c
onge
ners
006-008 cm
120-140 cm
440-472 cm
C93/95 C105/127
Results of In situ Field TrialResults of In situ Field Trial
0
5000
10000
15000
20000
25000
30000
35000
Sedge Pumpkin Tall Fescue
PCB
ext
ract
ed (u
g) Shoots
Roots
0
2000
4000
6000
8000
10000
Sedge Pumpkin Tall Fescue
PCB
s ex
tract
ed (u
g/m
2 )
ShootRoot
ConclusionsConclusions
• First in situ demonstration site of PCB phytoremediation in Canada
• No fugitive release of PCBs during field trial.
• Plants had high germination and success rates under in situ conditions
• Sedge, pumpkin and Tall Fescue show potential for PCB phytoextraction
Next Steps: Next Steps: Field Season 2005Field Season 2005
• Project funding confirmed
• Field season will begin in late June
• Soil will be homogenized before planting
• Increase plot sizes of Sedge and Tall Fescue
• Examine effect of shorter, more densely planted pumpkins
QUESTIONS?
PCA of soil and plant samples from PCA of soil and plant samples from PCBPCB--contaminated soilscontaminated soils
Principal Component 1 (36%)
Prin
cipa
l Com
pone
nt 2
(21%
)
Soil
Plant Root
Plant Shoot
-2 -1 0 1 2 3-3
-2
-1
0
1
2
241011015
2501125015
24195
24196
2501225016
24098
24005
10141038
24186
10181037
24194
24187
24104
24102 2411424096A1260
24108 240992411124105
2418325023
1035
24177
24179
25019
24178
1012
1022
24110
100724094
27097
1008
250211000
25025
24103
1010
1011
1020
25017
1004
10241023
1027
24100
1002
1034
24106
25020
24107
25024
1019
1031
1033
25027
1026
24182
24174
24095
100324173
25013
25009
24181
1006
25026
24175
1016
Site 060 shootsSite 060 roots
-1.0 -0.5 0.0 0.5 1.0-1.0
-0.5
0.0
0.5
1.0
C199C194
C196/203C195C206
C193C172/192
C174/181C183 C182/187
C205
C201
C177
C170_190
C185
C191C171
C175 C178
C180
C176
C208
C156
C198
C89/90/101
C110
C93_95C136
C86/97
C105/127C106/118
C92C84
C128C52_73
C139/149
C87/111/115
C138/158/160/163/164
C135/144
C143_134
C153
C151C146
C179
C133C132/168
C141
C130C129
tetrapentahexaheptaoctanona
PCB Molecular ShapePCB Molecular Shape
209 congeners total- non- and mono-orthosubstituted moleculesare coplanar or semi-coplanar,and widely recognized as serious environmental pollutants
3,3’,4,4’,5,5’ hexa-chlorobiphenyl = congener 169 (coplanar) - log Kow = 7.1
2,2’,4,4’,6,6’ hexa-chlorobiphenyl = congener 155 (staggered) - log Kow = 6.4
Molecular Geometry & Molecular Geometry & TranslocationTranslocation
0
0.2
0.4
0.6
0.8
1
soil root shoot
0
0.2
0.4
0.6
0.8
1
soil root shoot
non-ortho substituted congeners
multi-ortho substituted congeners