Phytoremediation
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by
Carla Huffman: cmhuffman@aol.com Harry Weekes: Harry_Weekes@communityschool.org Mimi Wallace: mwallace@socorro.k12.tx.us Nancy Wright: nwright@eznet.ent |
This activity corresponds with the following topics from the National Science Education Standards: Content Standards A, B, and C; Program Connection C; and Teaching Standards A through F.
Science as inquiry; access and choice among a variety of technologies; cross disciplinary; authentic assessment;appropriate manipulation of data; original analysis.
Table Of Contents:
Summary/Abstract
Instructor's Objectives
Target Age or Ability Group Audience
Teacher Instructions/Hints/Special Precautions
Materials & Equipment Needs
Background
The Student Lab
Lab Protocol Tested at Woodrow Wilson Institute, July 1998
Method of Evaluation/Assessment
Extension/Reinforcement/Additional Ideas
Extended Lab Protocol
National Science Standards
References
Summary/Abstract
Plants are currently being used by environmental scientists as a way to remove pollutants such as heavy metals from water or soil. This process is known as phytoremediation. Students will design an experiment to explore phytoremediation.Content connections: ecology, bioremediation, pollution, hyperaccumulation,
heavy metals
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Instructor's Objectives
Students will:- research phytoremediation
- develop a hypothesis
- design an experimental procedure
- collect and analyze data
- formulate conclusions
Target Audience or Age Group
- Biology, Chemistry, Environmental Science high school students and/or Advanced Placement courses.
Notes to the Teacher:
Pollution and contamination of the environment are now common place. Oil spills are no longer a surprise. Deforestation is old news. And phytoremediation and microbial activity in the rhizosphere are second nature. Huh? Phytoremediation and rhizosphere? What are these and what do they mean? Over the past decade scientists have been working on inventive ways of cleaning up the environment. Some of the most exciting emerging technologies are in the field of biological remediation. In short, biological remediation is the use of various organisms, from microbes to mustard plants, to facilitate the clean up and removal of substances ranging from heavy metals to dynamite. When plants are used in this process it is called phytoremediation. When bacteria and small soil organisms are used the process is called microbial remediation. The purpose of this laboratory is to look at the remediative effects of plants in the uptake of copper. The rhizosphere is the area immediately surrounding the plant roots where microbes and plants interact. This is the region where the greatest amount of phytoremediation occurs.Phyto and microbial remediation, which have no doubt been around for some time in a natural sense, have only recently been employed by people to assist in cleaning up contaminants and pollutants. Plants are currently being used for everything from binding heavy metals such as zinc and lead, to cleaning up radioactive material at Chernobyl and removing iron and sulfur from old mine tailings. The number of different contaminants is matched by the wide diversity of plant species utilized in phytoremediation; mustard plants bind heavy metals, cattails have been used for mine drainings, and poplar trees clean up TNT.
This lab focuses on the remediation of copper. So why choose copper? Well, for several reasons. First, since the Bronze Age humans have been using copper; subsequently, we have been adding copper and copper compounds into the environment. Many of these compounds accumulate over time and have deleterious effects in the environment. Since there is research describing the use of phytoremediation to remove copper, it should be possible to adapt those techniques to a lab for students. Second, copper and its associations with plants is very interesting. Copper is used by plants, and is an essential part of their photosynthetic pathways. Too little copper in the environment effects the metabolism; plants have reduced yields, impaired development and even reduced flowering. Too much copper seems to damage plant root systems, resulting in stunted growth (Lepp 1981). And yet, some plants do a good job of binding excess copper, thereby removing it from the soil. This lab will explore this last property. How well do various plants bind copper?
There are many other questions which might be raised and could be answered using the apparatus designed in this lab.
- Which types of plants are best in phytoremediation?
- Which chemicals can be best removed from the soil by phytoremediation?
- Is there a maximum amount of copper or other chemical which can be removed from the soil in this way?
This experiment is designed to be an open-ended inquiry experiment. The procedure used and tested at the Woodrow Wilson Institute, July 1998, is described below (Click here).
This activity will take a minimum of five (40 minute) class periods.
Helpful Hints:
- It was found that nylon hosiery is not a good soil filtering material as it blocks the flow of water. Paper towel or coffee filters work more effectively in soil drainage. However, copper sulfate solution is somewhat absorbed into the paper towel making the results less accurate.
- Good lab procedures should be followed at all times including wearing goggles as well as a lab apron.
- Excess copper sulfate solution should be remediated by placing 2-3 iron penny nails into the container. The copper will precipitate onto the nail and iron sulfate solution is formed in a single replacement reaction within several days. The color will change from blue to orange to clear with a muddy brown precipitate. Decant the liquid, and rinse down the sink. Place the precipitate in the trash.
Materials & Equipment Needs return to top
These are the minimum required materials. Others will vary based on what students select to investigate.
Reagents |
Materials |
Apparatuses (optional) |
| Distilled Water | 2 Liter plastic soda bottles | Spectrophotometer |
| Copper Sulfate (CuSO4) | 250 mL flask | Cuvettes |
| Copper Test Kit | 1 Liter flask | Analog or digital pH meter |
| Potting soil | ||
| Seeds (lettuce, radish, mustard, etc.) | ||
| 2 sheets of paper towels (as a filter) | ||
| Plastic disposable pipettes | ||
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Cork Borer |
Background
Vocabulary Necessary to Complete Activity: phytoremediation, bioremediationIn addition, students will need to research types of heavy metals, the processes of phytoremediation, and methods of chemical analysis depending upon their topic.
Methods of Evaluation/Assessment
- Students will create a poster presentation, formal lab report or oral report which will contain:
- background information (introduction)
- question investigated
- hypothesis (hypotheses)
- methods and materials
- data (graphs, tables etc.)
- analysis and conclusion
Extension/Reinforcement/Additional Ideas
- Students might be asked to observe the changes in the excess copper sulfate solution after adding iron nails and explain the chemical reactions occurring in the flask.
Copper sulfate + iron --> iron (II) sulfate + copper
References Including Web Addresses
Lepp, N.W. Effect of Heavy Metal Pollution on Plants, volume1: Effects of trace metals on plantfunctions. London: Applied Science Publishers. 1981.
Here are some sites and sources relating to phytoremediation, bioremediation and copper in plants:
http://www.smithsonianmag.com/smithsonian/issuesall/issues97/jul97/phenom_july97.html : This links to an article which gives good general information on phytoremediation and its current uses. This is written for a broad audience and will provide an excellent introduction and background for those learning about phytoremediation.
http://www.scientificamerican.com/1297issue/1297techbus4.html : This links to an article about the use of poplar trees for phytoremediation. This site provides good general information on the topic as well as more technical information. Even so, it is a valuable source for both beginner and intermediate.
http://www.ecological-engineering.com/phytorem.html : Like the first two articles, this site provides an excellent introduction and background to the field of phytoremediation. The page gives general as well as specific information on the uses of plants in cleaning up environmental contaminants. With the first two articles, it is a must for learning about this field.
http://www.msu.edu/course/css/853/Copper.html : This site deals with copper and its properties. There are diagrams and graphs which will introduce the browser to the structure of the copper molecule and to the significance of copper to plants. Although this is a more technical page, there is valuable information throughout. It is a good resource for understanding the importance of copper.
http://phytotech.com : This site is more specific to the 'industrial' uses of phytoremediation. Phytotech is a company in the business of phytoremediation. Although there is not too much general information, there is some background and introductory material on current uses of phytoremediation as a tool for business.
Please e-mail questions or comments to the authors above:
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