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.
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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
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.
Bibliography Aman, Mona. "..::How to Make Your Own Self-watering Pot::.." ..::How to Make Your Own Self-watering Pot::.. N.p., May 2009. Web. 18
Sept. 2013.
Brown, S. L., H. Compton, and N. T. Basta. Field Test of In Situ Soil Amendments at the Tar Creek National Priorities List Superfund Site.