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