The Heavy Metal Movement - AISES

The Heavy Metal

Movement McKalee Steen

10th grade

Grove High School

Grove, OK

Purpose The purpose of this project is to test Pancium virgatum (switchgrass) and

Schizachyrium scoparium (little bluestem grass) for their phytoextraction abilities

when grown in soil from the Tar Creek Superfund Site, and plant tissue analysis to

test heavy metal bioaccumulation within the plants.

Background Research

My Previous Study

•Switchgrass & Bermuda Grass were used successfully to remove heavy metals and phosphates via rhizofiltration.

Questions from study

•Can grasses be used to remove heavy metals from soil?

•Where does bioaccumulation of heavy metals occur within the plants?

Importance of Soil

•Crucial for rural and urban environments

•Contaminates can be passed to humans through agriculture

•Contaminated soil is difficult to remediate

Tar Creek History

• In NE Oklahoma

• Site for lead & zinc mining 1890-1959

•Mines flooded in 1979

• Spilling out acid mine drainage into Tar Creek along with astronomical levels of heavy metals.

Superfund Site

• 1980 Governor's task force investigates

• 1983 Tar Creek placed on National Priorities List

• 1984 Oklahoma Water Resources Board declares damage to Tar Creek irreversible

• Diversion dikes & filling of well holes by 1986

Tar Creek Future

•Removal of residence soil and chat piles continues

•Monitoring of stream and soil continues

•No real plans for large scale remediation

•Quapaw tribal lands involved, tribe is helping with clean up process & remediation ideas

Photo Credit: http://faculty.nwacc.edu/EAST_original/Environmental%20Geology,%20Fall%202008/Tar%20Creek%20Trip.htm

Background Research

Bioaccumulation

•Acquisition & movement of contaminants in plants

•Research suggest plant cell walls and root exudes take up heavy metals into plant roots

•Phytochelatins & vacuoles help bind up the heavy metals within the plant tissues, specifically the roots

Phytoremediation / Phytoextration

•Phytoremediation: use of plants to remediate soil, sludge, sediment or water

•Phytoextraction, the focus of this study, is a type of phytoremediation specific to using plants for removal of contaminants from soil

Tar Creek

Site of Soil Collection

Heavy Metals Found in this Study Bioremediation Plan

• Acceptable Levels for Soil:

• 200ppm Lead

• 1100ppm Zinc

• 0.44ppm Cadmium

• 185ppm Iron

• 40ppm Manganese

• 72ppm Nickel

• Levels in untreated soil

collected at Tar Creek:

• 551.80ppm Lead

• 13380ppm Zinc

• 68.68ppm Cadmium

• 47898ppm Iron

• 1330ppm Manganese

• 144.10ppm Nickel

• Phytoremediation using Switchgrass and Little Bluestem Grass.

• Bioaccumulation measurements in plant tissue

Diagram created by McKalee Steen using Microsoft Digital Image Pro software.

Vacuolar Compartmentalization of Heavy Metals Switchgrass

• Pancium virgatum

• Strong deep root system

• Native to U.S.

• Used in various studies for phytoremediation

Little Bluestem

• Schizachyrium scoparium

• Deep, fibrous root system

• Native to U.S.

• Used in this study because it was found growing along Tar Creek.

Photos of Little

Bluestem growing at

collection site.

Notice the chat pile

in the background. Photos taken by

Rebecca Jim

Hypotheses

Phytoextraction

I. It is hypothesized that both Pancium virgatum and Schizachyrium

scoparium will be effective in the phytoextraction of heavy metals.

II. It is further hypothesized that Schizachyrium scoparium will be more

effective at phytoextraction of heavy metals than Pancium virgatum

because Schizachyrium scoparium was found growing along Tar Creek.

Bioaccumulation

I. It is hypothesized that both grasses will bioaccumulate the heavy

metals at lower concentrations than what is extracted from the soils

by the grasses. This is hypothesized because of research supporting

biotransformation.

II. It is further hypothesized that some heavy metals will be at higher

concentrations within the root system while other heavy metals will be

in higher concentrations in the plant tissues above ground.

Methods: Soil Collection & Preparation

Permission was obtained to enter the Tar Creek Superfund Site for soil

Collections. Rebecca Jim from the LEAD agency in Miami, Oklahoma helped with

this and accompanied me to the site at Douthat Bridge in Ottawa County,

Oklahoma. A composite sample was taken from several locations above and

below the bridge.

Northeast of the bridge, a mine drains acidic waters into Tar Creek. To the

Northwest sits one of the area’s famous chat piles created from mine tailings. A

pool of water which washes off the pile seeps slowly into Tar Creek. All three

sources of water merge here and flow under the bridge.

Soil was prepared by first sifting out large particles and organic material. Seed

starter potting soil was added to the Tar Creek soil. The soil was wetted before

stirring to make a homogenous mixture.

Methods: Planting and Growth of Grasses

40 1500 mL pots were purchased. Approximately 12 in. pieces of wick were cut to

go through bottom of pot. Then, a piece of filter paper was placed in the bottom

of the pot, the wick was pulled through. Next, 200 mL of pea gravel were

measured and poured in bottom of the pot. Lastly, 1000 mL of soil mixture was

measured and put on top of pea gravel.

A digital scale was used to measure 1.5 grams of grass seed per pot (15 pots with

Switchgrass and 15 pots Little Bluestem). 4 pots were prepared as above with no

seeds. This was the untreated soil control. The remaining six pots were prepared

with only potting soil (3 SG and 3 BS). This was the plant control.

All pots were placed in trays. Surface was lightly misted with distilled water daily

until seeds germinated. Every 2-3 days, or as needed, the plants were watered

by pouring distilled water into the bottom of the tray (Approx. 500 mL). Once

every 2 weeks plants were watered with a soluble fertilizer and water mix (16

grams of fertilizer per 1 gallon of water). Twice a week, plant trays were rotated

for equal lighting of all plants.

Methods: Preparation of Samples & Testing Equipment was cleaned with acid wash, tap water, & deionized (DI) water. After

11, 15 & 19 weeks, 5 pots were selected for each grass variety. Soil and grass

were separated, and soil was left in shallow tray to air dry. Grass roots were

rinsed under tap water until all soil was removed. Roots were removed from the

plants above ground growth. Plant material was rinsed in a series if DI water

baths. Grass was placed in a glass pan in a ventilated oven at 60-65 degrees

Celsius for 24-48 hours. Dry biomass was recorded. Samples were placed in clean

labeled jars.

Samples were ground up using a micro mill. The micro mill was cleaned

thoroughly after each sample was milled. 0.5 grams of milled material was

measured and placed into a MARS microwave tube. 10 mL of nitric acid was

added into the tube with sample. Waiting period was: Plant material 5-10 min.,

Soil none. Lid was secured and samples were microwaved for 30 minutes.

Contents were removed from tube into 15 mL viles and centrifuged for 15

minutes.

Using supernatant from digested samples, the samples were diluted: 1 mL of

sample into 9 mL of DI water for 10x dilution, 0.1 mL of sample into 9.9 mL of DI

water for 100x dilution, 0.1 mL of sample into 49.9 mL of DI water for 500x

dilution. Using standard samples, the ICP-OES machine was prepared for testing.

Finally, the samples were ran in the ICP-OES machine to analyze samples for the

following elements in mg/kg (ppm): Lead, Cadmium, Zinc, Iron, Manganese, &

Nickel.

0.928

2.244

0.406

1.188

0.708

2.240

0.636

1.668

0.402

2.864

0.610

4.388

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

4.500

SG RootsWk 11

SG ShootsWk 11

SG RootsWk 15

SG ShootsWk 15

SG RootsWk 19

SG Shoots19

BS RootsWk 11

BS ShootsWk 11

BS RootsWk 15

BS ShootsWk 15

BS RootsWk 19

BS ShootsWk 19

Gra

ms

Average Grams of Dry Biomass per Container

For each collection, 5 growing pots from each group were harvested. The Biomass was

measured with a digital scale after collection, washing and drying for 24-48 hours in a

ventilated oven. As you can see from the graph, the little bluestem roots were lighter

weight than the switchgrass roots but the shoots had a greater biomass. Over all, little

bluestem looked healthier throughout the growing process as compared to switchgrass,

especially during week 15 and 19 collections.

Sample Ca Cd Fe Mg Mn Ni Pb Zn

Control Plant Soil (potting soil) 70210 1.52 7744 11200 508 35.1 0.00 277

Control Avg. (no plants) 17138 68.68 47898 5383 1330 144.1 551.8 13380

Switchgrass Week 11 14970 56.51 40130 4451 1272 236.6 462.8 11770



Bluestem Week 11 13620 51.59 36000 4444 1046 161.6 391.5 11760

Bluestem Week 15 9610 25.89 21560 3467 561 94.3 271.6 5697

ICP-OES Soil Analysis

Comparison of Soil with and with-out Bioremediation: Mean Result mg/kg (ppm)

Soil Data

Mean

Results and

Residual

Standard

Deviation

Sample Ca Cd Fe Mg Mn Ni Pb Zn

Control Avg. (no plants) 3.24 3.75 1.82 1.60 2.86 4.97 3.54 0.78

Switchgrass Week 11 1.57 4.70 2.84 2.60 1.22 4.94 7.49 2.62



Bluestem Week 11 0.75 1.05 2.96 4.82 2.16 1.37 1.56 2.85

Bluestem Week 15 1.77 1.43 1.14 3.16 3.27 1.92 1.25 2.91

Bluestem Week 19 2.39 0.71 2.83 3.13 0.60 9.12 0.35 0.11

Residual Standard Deviation (% RSD = (SD / Mean Result) * 100)

*RSD results under 20% are considered statistically accurate results

When running a sample, an ICP-OES machine takes 3 readings and then gives the average of those

readings. Residual Standard Deviation (RSD) is a measurement of how far apart those readings are. If

the readings are 20% or less they are considered accurate, or in other words each reading was not very

far apart from each other. However, the smaller the reading, the more chance the reading has of

being over 20% RSD because the slightest difference with a small number will cause a greater RSD.

Plant Tissue Cd Fe Mn Ni Pb Zn

SG Roots Wk 11 10.470 8112.0 155.90 155.00 46.820 1845.0

SG Shoots Wk 11 2.479 2903.0 125.80 108.00 6.175 413.7

SG Roots Wk 15 12.350 8718.0 184.20 67.66 38.460 1926.0

SG Shoots Wk 15 2.157 5008.0 194.40 293.00 3.583 530.1

SG Roots Wk 19 15.870 2170.0 163.70 13.14 25.190 2101.0

SG Shoots Wk 19 2.311 582.4 191.7 24.94 5.553 524.7

BS Roots Wk 11 15.91 7336.0 225.80 128.70 56.980 1978.0

BS Shoots Wk 11 1.884 1933.0 90.38 75.43 4.204 238.4

BS Roots Wk 15 17.950 5201.0 175.90 123.30 23.900 1759.0

BS Shoots Wk 15 1.217 4506.0 137.50 283.60 1.350 136.8

BS Roots Wk 19 57.380 7851.0 274.40 43.07 93.20 3698.0

BS Shoots Wk 19 2.522 278.1 100.00 17.50 1.195 631.2

ICP-OES Plant Tissue Analysis

Comparison of root tissue and shoot tissue: Mean Results mg/kg (ppm)

Plant Tissue Ca Cd Fe Mg Mn Ni Pb Zn

SG Roots Wk 11 1.80 1.77 1.97 1.43 0.43 1.75 3.16 2.45

SG Shoots Wk 11 1.50 1.52 3.28 3.75 1.34 1.79 7.72 0.87

SG Roots Wk 15 1.52 2.20 4.67 5.80 3.16 2.16 1.20 1.26

SG Shoots Wk 15 1.68 1.83 1.54 2.93 2.89 0.57 8.03 0.94

SG Roots Wk 19 2.18 0.62 1.94 1.52 3.31 1.31 3.03 1.42

SG Shoots 19 1.22 1.00 1.55 1.28 1.76 1.32 5.29 0.77

BS Roots Wk 11 4.45 1.25 5.07 4.60 5.55 1.53 0.81 3.29

BS Shoots Wk 11 2.06 2.08 1.00 0.89 1.50 0.21 8.71 0.64

BS Roots Wk 15 3.67 1.97 3.15 2.20 2.27 2.15 6.78 1.50

BS Shoots Wk 15 1.25 3.12 0.83 2.71 0.80 1.96 25.52 0.81

BS Roots Wk 19 1.62 0.36 0.18 1.37 0.15 2.40 1.64 0.53

BS Shoots Wk 19 2.71 0.16 2.28 2.05 2.05 0.54 22.73 1.98

Residual Standard Deviation (% RSD = (SD / Mean Result) * 100)

*RSD results under 20% are considered statistically accurate results

Plant Tissue

Data Mean

Results and

Residual

Standard

Deviation

The two high readings for

lead are because those two

readings are so low that a

small standard deviation

results in a large RSD.

11.01

551.80

462.80 480.90

624.60

391.50

271.60

546.10

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00

Potting Soil Control SG Wk 11 SG Wk 15 SG Wk 19 BS Wk 11 BS Wk 15 BS Wk 19

mg/K

g

Soil Analysis for Lead

-16.13% -12.85%

13.19%

-29.05%

-50.78%

-1.03%

-100.00%

-80.00%

-60.00%

-40.00%

-20.00%

0.00%

20.00%

40.00%

60.00%

80.00%

SG 11 Wk SG 15 WK SG 19 Wk BS 11 Wk BS 15 WK BS 19 Wk

Pere

centa

ge

Soil Lead Levels: Percent Difference from Control

0.38 2.11

46.82

6.18

38.46

3.58

25.19

3.87

56.98

4.20

23.90

1.35

93.20

1.20

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

ControlRoots

ControlShoots

SGRootsWk 11

SGShootsWk 11

SGRootsWk 15

SGShootsWk 15

SGRootsWk 19

SGShoots

19

BSRootsWk 11

BSShootsWk 11

BSRootsWk 15

BSShootsWk 15

BSRootsWk 19

BSShootsWk 19

mg/K

g

Plant Tissue Analysis for Lead

An acceptable level of lead in soil is 200 ppm. The level of lead in the

control/untreated soil was 2.759 times the acceptable amount. Little

Bluestem was more efficient at remediating lead, and was significantly

lower than the control soil during week 11 & week 15. Little Bluestem also

had higher concentrations of metals in the plant roots during week 19. All

lead levels in plant shoots was lower than levels in roots during all

collections. Health effects of lead include fatigue, poor muscle

coordination, brain and nervous system damage, and in extreme situations,

death. Young children are at greatest risk for high lead soil levels.

Statistical Analysis of Soil Samples

Treated vs Untreated Soil: Using a One-Way Analysis of Variance (ANOVA)

Treatment Date Metal P-Value Significance Higher or Lower

than Untreated

Switchgrass Week 11 Lead <0.05 Significant Lower

Little Bluestem Week 11 Lead <0.01 Very Significant Lower

Switchgrass Week 15 Lead <0.05 Significant Lower

Little Bluestem Week 15 Lead <0.01 Very Significant Lower

Switchgrass Week 19 Lead <0.05 Significant Higher

Little Bluestem Week 19 Lead >0.05 Not Significant Lower

Red dotted line represents the recommended levels for soil

277

13380

11770

13270 13820

11760

5697

14080

0

2000

4000

6000

8000

10000

12000

14000

16000


mg/K

g

Soil Analysis for Zinc

-12.03% -0.82%

3.29%

-12.11%

-57.42%

5.23%

-100.00%

-80.00%

-60.00%

-40.00%

-20.00%

0.00%

20.00%

40.00%

60.00%

80.00%


Pere

centa

ge

Soil Zinc Levels: Percent Difference from Control

129.3 141.5

1845.0

413.7

1926.0

530.1

2108.0

547.8

1978.0

238.4

1759.0

136.8

3698.0

631.2

0.0

500.0

1000.0

1500.0

2000.0

2500.0

3000.0

3500.0

4000.0

ControlRoots

ControlShoots

SGRootsWk 11

SGShootsWk 11

SGRootsWk 15

SGShootsWk 15

SGRootsWk 19

SGShoots

19

BSRootsWk 11

BSShootsWk 11

BSRootsWk 15

BSShootsWk 15

BSRootsWk 19

BSShootsWk 19

mg/K

g

Plant Tissue Analysis for Zinc

Acceptable Zinc levels in soil are 1100 ppm. The untreated soil was 12.163

times higher than acceptable levels. Both treatments were efficient at

removing some zinc through week 11 but only little bluestem was

significantly lower than the control during week 15. In week 19 testing,

both treated soils experienced a spike in zinc levels. Zinc is a needed

nutrient for both plants and animals but overexposure to zinc through

inhalation can cause nausea, fever and pulmonary inflammation. In

extreme cases, death by respiratory failure. No data on ingestion of

extreme levels of zinc could be found.




than Untreated

Switchgrass Week 11 Zinc <0.01 Very Significant Lower

Little Bluestem Week 11 Zinc <0.01 Very Significant Lower

Switchgrass Week 15 Zinc <0.05 Significant Lower

Little Bluestem Week 15 Zinc <0.01 Very Significant Lower

Switchgrass Week 19 Zinc <0.05 Significant Higher

Little Bluestem Week 19 Zinc <0.01 Very Significant Higher

In the control soil cadmium is 156.091 times the acceptable amount of

0.44ppm. Both grasses lowered the cadmium levels significantly as

compared to the untreated soil for weeks 11, 15 & 19. Little bluestem was

slightly more effective, especially on week fifteen. Inhaling cadmium can

cause severe damage to the lungs, and possibly even death. Exposure to

cadmium over time can result in the build up of cadmium in tissues,

especially the kidneys, which could result in kidney failure.

1.52

68.68

56.51 58.03 59.00

51.59

25.89

61.59

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00


mg/K

g

Soil Analysis for Cadmium

-17.72% -15.51% -14.09% -24.88%

-62.30%

-10.32%

-100.00%

-80.00%

-60.00%

-40.00%

-20.00%

0.00%

20.00%

40.00%

60.00%

80.00%


Pere

centa

ge

Soil Cadmium Levels: Percent Difference from Control

0.379 0.574

10.470

2.479

12.350

2.157

15.870

3.155

15.910

1.884

17.950

1.217

57.380

2.522

0.000

10.000

20.000

30.000

40.000

50.000

60.000

70.000

80.000

Control Roots SG Roots Wk11

SG Roots Wk15

SG Roots Wk19

BS Roots Wk11

BS Roots Wk15

BS Roots Wk19

mg/K

g

Plant Tissue Analysis for Cadmium




than Untreated

Switchgrass Week 11 Cd <0.01 Very Significant Lower

Little Bluestem Week 11 Cd <0.01 Very Significant Lower





Iron in control soil was 258.91 times higher than the recommended level of

185ppm for soil. Both grasses significantly lowered iron below the

untreated soil but little bluestem was able to and keep it below the

untreated soil iron levels, while Switchgrass did not at week 19. Iron also

had higher concentrations in the roots as compared to the shoots. Health

effects of iron include increased chance of lung cancer if inhaled too often.

Iron toxicity death is rare and young children are at greatest risk for iron

toxicity.

7744

47898

40130

44480

54720

36000

21560

43610

0

10000

20000

30000

40000

50000

60000


mg/K

g

Soil Analysis for Iron

-16.22% -7.14%

14.24%

-24.84%

-54.99%

-8.95

-100.00%

-80.00%

-60.00%

-40.00%

-20.00%

0.00%

20.00%

40.00%

60.00%

80.00%


Pere

centa

ge

Soil Iron Levels: Percent Difference from Control

111.8 304.4

8112.0

2903.0

8718.0

5008.0

2170.0

520.3

7336.0

1933.0

5201.0

4506.0

7851.0

278.1

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

9000.0

10000.0

ControlRoots

ControlShoots

SGRootsWk 11

SGShootsWk 11

SGRootsWk 15

SGShootsWk 15

SGRootsWk 19

SGShoots

19

BSRootsWk 11

BSShootsWk 11

BSRootsWk 15

BSShootsWk 15

BSRootsWk 19

BSShootsWk 19

mg/K

g

Plant Analysis for Iron




than Untreated

Switchgrass Week 11 Iron <0.01 Very Significant Lower

Little Bluestem Week 11 Iron <0.01 Very Significant Lower

Switchgrass Week 15 Iron <0.01 Very Significant Lower


Switchgrass Week 19 Iron <0.01 Very Significant Higher


Control soil was 33.25 times higher than the recommended level of 40ppm

Mn for soil. Little bluestem was more effective than switchgrass when

removing manganese. However, an interesting observation to point out is

that the concentrations of manganese in the plant material was about the

same in the roots and the shoots for switchgrass, while bluestem had

higher concentrations in the roots. Inhaling even small amounts of

manganese may lead to manganese accumulation and adverse health

effects including damage to the lungs, liver, kidney and central nervous

system. Some symptoms are very similar to Parkinson’s disease.

508

1330 1272

1171

1761

1046

561

1368

0

200

400

600

800

1000

1200

1400

1600

1800

2000


mg/K

g

Soil Analysis for Manganese

-4.36% -11.95%

32.41%

-21.35%

-57.82%

2.86%

-100.00%

-80.00%

-60.00%

-40.00%

-20.00%

0.00%

20.00%

40.00%

60.00%

80.00%


Pere

centa

ge

Soil Manganese Levels: Percent Difference from Control

75.54

55.71

155.90

125.80

184.20 194.40 191.7

184.50

225.80

90.38

175.90

137.50

274.40

100.00

0.00

50.00

100.00

150.00

200.00

250.00

300.00

ControlRoots

ControlShoots

SGRootsWk 11

SGShootsWk 11

SGRootsWk 15

SGShootsWk 15

SGRootsWk 19

SGShoots

19

BSRootsWk 11

BSShootsWk 11

BSRootsWk 15

BSShootsWk 15

BSRootsWk 19

BSShootsWk 19

mg/K

g

Plant Analysis for Manganese




than Untreated

Switchgrass Week 11 Mn >0.05 Not Significant Lower

Little Bluestem Week 11 Mn <0.01 Very Significant Lower

Switchgrass Week 15 Mn <0.01 Very Significant Lower

Little Bluestem Week 15 Mn <0.01 Very Significant Lower

Switchgrass Week 19 Mn <0.01 Very Significant Higher

Little Bluestem Week 19 Mn >0.05 Not Significant Higher

Nickel acceptable levels in soil are 72 ppm. Therefore the Nickel

concentrations in the control soil are 2.006 times higher than that. Both of

the grasses did a remarkable job removing Nickel from the soil, bringing it

down to acceptable levels by week 19. Interestingly, the nickel

concentrations were higher in the shoots of the plant material for week 15

of both grasses. Nickel is dangerous when airborne and can effect the

respiratory system negatively when inhaled.

35.1

144.1

236.6

105.3

17.7

161.6

94.13

11.4

0.0

50.0

100.0

150.0

200.0

250.0


mg/K

g

Soil Analysis for Nickel 64.19%

-26.93%

-87.72%

12.14%

-34.56%

-92.09% -100.00%

-80.00%

-60.00%

-40.00%

-20.00%

0.00%

20.00%

40.00%

60.00%

80.00%


Pere

centa

ge

Soil Nickel Levels: Percent Difference from Control

14.01 2.09

155.00

108.00

67.66

293.00

24.94 13.32

128.70

75.43

123.30

283.60

43.07

17.50

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

ControlRoots

ControlShoots

SGRootsWk 11

SGShootsWk 11

SGRootsWk 15

SGShootsWk 15

SGRootsWk 19

SGShoots

19

BSRootsWk 11

BSShootsWk 11

BSRootsWk 15

BSShootsWk 15

BSRootsWk 19

BSShootsWk 19

mg/K

g

Plant Tissue Analysis for Nickel




than Untreated

Switchgrass Week 11 Nickel <0.01 Very Significant Higher

Little Bluestem Week 11 Nickel >0.05 Not Significant Higher

Switchgrass Week 15 Nickel <0.01 Very Significant Lower

Little Bluestem Week 15 Nickel <0.01 Very Significant Lower

Switchgrass Week 19 Nickel <0.01 Very Significant Lower

Little Bluestem Week 19 Nickel <0.01 Very Significant Lower

Analysis: Phytoextraction The hypothesis that both Pancium virgatum and Schizachyrium scoparium

would be effective in the phytoextraction of heavy metals was partially accepted.

Both Pancium virgatum and Schizachyrium scoparium were able to remove heavy metals from the soil.

However, nickel was the only metal brought down to acceptable levels.

Also, while the plants were able to remove some heavy metals, by week nineteen the grasses were not removing metals as well. It is theorized that the extreme levels of heavy metals stressed the young plants during this time frame.

The hypothesis that Schizachyrium scoparium would be more effective than Pancium virgatum was accepted.

Over all, the soil with Schizachyrium scoparium had lower concentrations of heavy metals as compared to the soil Pancium virgatum was grown in. This was true for every metal during all three measurements (weeks 11, 15 & 19) with the exception of Zinc in week 19.

Week 15 was optimal for Schizachyrium scoparium. Every metal was at its lowest level during that time frame in this experimental group.

Also, Schizachyrium scoparium plant growth remained healthier looking throughout the testing period.

Analysis: Bioaccumulation The hypothesis that both grasses will bioaccumulate the heavy metals at lower

concentrations than what is extracted from the soils was partially accepted.

For the first two tests the grasses seemed to follow this general trend.

This suggests that the plants were able to biotransform some of the metals.

However, by week nineteen there were more metals in the plants than what was removed from the soil. In fact there was an increase in the amount of metals in the soil and an increase in the amount of metals in the plants, which was not expected. A probable explanation would be that the plants may have experienced vacuolar rupture leading to plant stress and a release of metals to both soil and plant tissues.

The hypothesis that some heavy metals would be at higher concentrations within the roots system while other heavy metals would be higher in the plant tissues above ground was also accepted.

Most of the metals were at a higher concentration in the roots as compared to the shoots. This is probably because of the vacuolar compartmentalization process in the plant roots.

However, Pancium virgatum and Schizachyrium scoparium had higher levels of nickel in the shoots during week fifteen of growth. Also, week fifteen and nineteen Pancium virgatum had slightly higher levels of manganese in the shoots. This is probably because nickel and manganese are micronutrients needed by the plants, so these two metals moved more freely to the shoots.

Impacts Large scale:

Tar Creek and the surrounding area is in great need of remediation

Tar Creek Superfund Site is situated on Quapaw Tribal Lands and the Tribe has shown interest in the results of this study and the use of grasses in tribal remediation plans.

Some bioremediation is being done on a small scale at one mine drainage site.

Native grasses could be introduced inexpensively on a large scale at all mine drainage sites.

Other sites such as military bases known for heavy metal contamination could incorporate native grasses for bioremediation.

Small scale:

Non-point source pollution:

Native grasses could be used easily in rain gardens to remove contaminants from storm water runoff.

Large native grasses would also do well in artificial wetlands designed as a last step of wastewater treatment.

Buffer and riparian zones between agriculture or industry and surface waters.

Researchers exploring phytoremediation might also be interested in these results.

Conclusion The purpose of this project was to test Pancium virgatum and Schizachyrium scoparium

for their phytoextraction abilities when grown in soil from the Tar Creek superfund site, and a plant tissue analysis to test heavy metal bioaccumulation within the plants. This purpose was achieved.

Good News:

The above ground shoots contained the lowest readings for most heavy metals.

Although the shoots in the two test groups remained higher in heavy metals than the control plants, it is promising that the bioaccumulation was higher in the roots as compared to the shoots.

Challenges:

Growing time needed for plants.

Grasses were grown from seed and were young, tender plants which may explain the stress shown by soil heavy metal increases during the week 19 collection.

Grasses took longer than normal to grow to a testable size.

These extreme amounts were the probable cause of the slow growth of the grasses.

Further studies:

Extend growing time, to see the trends that the plants follow over many months.

Analyze Little Bluestem at the Tar Creek Site to see how a plant grown long term under extreme conditions is able to bioaccumulate heavy metals.

Get seeds from plants at Tar Creek that are possibly more evolved and better adapted to the conditions as an additional test group.

Acknowledgements

I would like to thank the LEAD Agency for valuable insight and to

Rebecca Jim of the LEAD agency for helping with the soil collections

and for taking pictures at the collection site.

I would also like to thank Steve Nikolai, lab manager at the Grand

River Dam Authorities Eco-Systems and Educational Center’s

Laboratory for allowing me to work in his lab and for teaching me how

to use the equipment.

I would also like to thank Dr. Darrell Townsend of Grand River Dam

Authority for allowing me to bring my samples to the lab for analysis.

I would lastly like to thank my mother and teacher Keli Steen for her

continued support and guidance throughout this project.

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Photo Credits Collection site pictures were taken by Rebecca Jim. Laboratory Pictures were taken by Keli Steen or McKalee Steen

Documents

The Heavy Metal Movement - AISES