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
Switchgrass Week 15 14630 58.03 44480 4841 1171 105.3 480.9 13270
Switchgrass Week 19 1830 59.00 54720 6414 1761 17.7 624.6 13820
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
Switchgrass Week 15 1.67 1.12 2.47 0.91 1.46 1.64 0.76 1.21
Switchgrass Week 19 1.36 1.56 1.37 3.77 3.09 2.59 0.70 1.96
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
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 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%
SG 11 Wk SG 15 WK SG 19 Wk BS 11 Wk BS 15 WK BS 19 Wk
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.
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 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
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 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%
SG 11 Wk SG 15 WK SG 19 Wk BS 11 Wk BS 15 WK BS 19 Wk
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
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 Cd <0.01 Very Significant Lower
Little Bluestem Week 11 Cd <0.01 Very Significant Lower
Switchgrass Week 15 Cd <0.01 Very Significant Lower
Little Bluestem Week 15 Cd <0.01 Very Significant Lower
Switchgrass Week 19 Cd <0.01 Very Significant Lower
Little Bluestem Week 19 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
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 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%
SG 11 Wk SG 15 WK SG 19 Wk BS 11 Wk BS 15 WK BS 19 Wk
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
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 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
Little Bluestem Week 15 Iron <0.01 Very Significant Lower
Switchgrass Week 19 Iron <0.01 Very Significant Higher
Little Bluestem Week 19 Iron <0.01 Very Significant Lower
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
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 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%
SG 11 Wk SG 15 WK SG 19 Wk BS 11 Wk BS 15 WK BS 19 Wk
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
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 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
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 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%
SG 11 Wk SG 15 WK SG 19 Wk BS 11 Wk BS 15 WK BS 19 Wk
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
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 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