Phytoremediation of Soil Contaminants

Paul SchwabKathy Banks

Purdue University

Phytoremediation Applications

Phytoextraction – removal of contaminants from soils.Phytodegradation – plant degradation of contaminants after uptake.Phytoaccumulation – contaminant accumulation in above ground biomass.

Phytoremediation Applications

Rhizosphere Degradation – enhancement of rhizosphere microbial bioremediation. Groundwater Interception – plants with large water requirements reduce contaminated groundwater movement. Living Caps – Reduction of leachate in landfills.

ROOTINGCHARACTERISTICS

TRANSPIRATION

CONTAMINANT(S)

PHYTOREMEDIATION

PLANT SPECIES

MICROBIALPOPULATIONS

Phytoremediation Processes Organic Contaminants

UPTAKE BIOMASS

CONTAMINANT(S)

PHYTOREMEDIATION

PLANT SPECIES

SOILCHARACTERISTICS

Phytoremediation Processes Heavy Metal Contaminants

AdvantagesLow-cost approach.Aesthetically pleasing and appealing to the public.Site use and remediation can occur simultaneously.

Disadvantages

Long time period required for remediation.Unknown impact on ecosystems and bioavailability.Scientific understanding of mechanisms is limited.

Field Sites

Port Hueneme Site - Fuel oil contaminated soil located in test cells at a DoD National Test Site.Bedford Site - Manufactured gas plant site with high PAH contamination at depths of 3 to 6 feet.

Port Hueneme Site (1997-2000)

Site was located at the Port Hueneme DOD National Test Site.Study area consisted of 60’ x 100’ plots with three treatments and four replicates. Fertilizer and irrigation was used as needed. Soil samples were analyzed for petroleum contaminants, microbial characteristics, and toxicity for 30 months.

Above-Ground BiomassPort Hueneme Site

0

200

400

600

800

3 6 9 11 14 18 21 24 26 29

Bio

mas

s (g

/sq.

m) FESCUE

MIX

LSD = 121

Time (months)

Microbial Analysis (Total Plate Counts)Port Hueneme Site

5

6

7

8

3 6 11 14 18 21 24 26 30

Log

CFU

s

BAREFESCUEMIX

Time (months)

Microbial Analysis (Petroleum Degraders)Port Hueneme Site

5

6

7

8

Bare Fescue Mix

Log

MPN

s

a

b b

Plant Treatment

Toxicity Analysis (Germination)Port Hueneme Site

0

40

80

120

6 9 11 14 18 21 24 26 29

% G

erm

inat

ion

UNVEG.FESCUEMIX

LSD = 17%

Time (months)

TPH Degradation (%)Port Hueneme Site

0

10

20

30

40

6 9 12 14 21 24

% T

PH D

egra

datio

n

BAREFESCUEMIX

LSD = 9.1%

Time (months)

Contaminant Analysis (PAHs)Port Hueneme Site

0

0.4

0.8

1.2

0 6 9 18

Tota

lPA

Hs

(mg/

kg)

BAREFESCUEMIX

Time (months)

Bedford Site (1999-2002)

MGP site with PAH contamination at depths between 3 and 6 feet.Two treatments are being compared; hybrid poplar/grass cover and natural attenuation.Fertilization and irrigation is used as needed.Soil from three depths are being analyzed for contaminant concentration, microbial characteristics, and toxicity over the three year study.

Toxicity Analysis (Germination)Bedford Site

0

20

40

60

80

100

0 6 12 18

% G

erm

inat

ion

UnvegetatedVegetated

Time (months)

Toxicity Analysis (Earthworm)Bedford Site

0

40

80

120

0 6 12 18

Bio

mas

s (m

g)

UnvegetatedVegetated

Time (months)

Microbial Analysis (Petroleum Degraders)Bedford Site

0

2

4

6

8

6 12 18

Log

CFU

UnvegetatedVegetated

Time (months)

Contaminant Analysis (PAHs)Bedford Site

0

100

200

300

0 6 12 18

Ant

hrac

ene

(mg/

kg) Unvegetated

Vegetated

Time (months)

Supporting Greenhouse StudyBedford Site

Soil cores were taken in the field and placed in the greenhouse.Trees (ash, poplar, and willow) were established in the columns with two takedowns (9 and 18 months).Water was added to the columns from the bottom to simulate field conditions.Contaminant concentrations, microbial characteristics, and toxicity was assessed.

0

2

4

6

8

Control Ash Poplar Willow

Treatment

log

(Pet

role

um D

egra

ders

)

9 months18 months

Microbial Analysis (Petroleum Degraders)Bedford Greenhouse Study

0

100

200

300

Napth. Phen. Chrys. Pyr. B[a]P

PAH

con

c. (m

g/kg

)

ControlAshPoplarWillow

Contaminant Analysis (PAHs)Bedford Greenhouse Study

Summary and OutlookPhytoremediation of Petroleum Contaminants

Phytoremediation of petroleum contaminated soils has been successfully tested in the field.The impact of vegetation is related to the aging of the contaminants.Petroleum contaminated soil does not appear to be toxic to plants or invertebrates.PAH degradation parallels remediation of total petroleum hydrocarbons.The success of phytoremediation is closely related to the ability of roots to explore the soil.