• Bioremediation / Phytoremediation Science Fair Projects and Experiments
  

Phytoremediation is the technical term used to describe the treatment of environmental problems (bioremediation) through the use of plants.

Certain plants are able to extract hazardous substances such as arsenic, lead and uranium from soil and water. One example is alpine pennycress (Brassicaceae), a plant which naturally accumulates high levels of cadmium and zinc from the environment. Alpine pennycress is therefore known as a hyperaccumulator of these metals, which in unnaturally high levels would be poisonous to many plants. Another example of a hyperaccumulator is the bracken fern. This fern extracts arsenic from the soil at a much greater rate than other plants. This arsenic is stored in the fern's leaves at as much as 200 times that present in the soil, thus enabling effective and practical clean-up programs. Sunflowers were also used to clean up uranium after the Chernobyl accident.

In the case of organic pollutants, such as pesticides, explosives and industrial chemicals, certain plants may render these substances non-toxic by their metabolism.

Breeding programs and genetic engineering are powerful methods for enhancing natural tendencies of plants, or for introducing these tendencies into alternative types of plants which might be more suitable for the environmental conditions.

The range of biological treatments for environmental problems, as described by the term phytoremediation, actually consists of several specific processes:

• Phytoextraction - uptake of substances from the environment, with storage in the plant (phytoaccumulation [see below]).
• Phytostabilisation - reducing the movement or transfer of substances in the environment. For example, limiting the leaching of substances contaminating soil.
• Phytostimulation - enhancement of microbial activity for the degradation of contaminants, typically around plant roots.
• Phytotransformation - uptake of substances from the environment, with degradation occurring within the plant (phytodegradation).
• Phytovolatilization - removal of substances from the soil or water with release into the air, possibly after degradation.
• Rhizofiltration - the removal of toxic metals from groundwater.

See also:

• Biodegradation
• Bioremediation
• John Todd - cofounder of the New Alchemy Institute

External links

• International Journal of Phytoremediation - devoted to the publication of current laboratory and field research describing the use of plant systems to remediate contaminated environments.
• Using Plants To Clean Up Soils - from Agricultural Research magazine
• Phytoremediation website hosted by the Missouri Botanical Garden - Review Articles, Conferences, Phytoremediation Links, Research Sponsors, Books and Journals, and Recent Research.

Phytoextraction

Phytoextraction (also known as phytoaccumulation) is a form of phytoremediation, in short phytoextraction is the process of ‘removing contaminants from soil or sediment by having plants take them up and store then in aboveground, harvestable tissues.’ (Brookhaven National Laboratory, 2000). Phytoextraction is a rapidly growing process that many people across the planet are taking up. Phytoextraction generally works better with extracting heavy metals from soil rather than organic compounds or chemicals. It is a clean, efficient, cheaper and nature friendly alternative to regular excavation of soil. It also ‘accumulates the contaminants in a much smaller amount of material to be disposed of (the contaminated plants) than does excavation of soil or sediment.’ (Brookhaven National Laboratory, 2000).

In phytoextraction, the plant absorbs the contaminant from the soil, through its roots and takes the contaminants above soil-level to its leaves and stems, or the plant will absorb the contaminant and will store it in its roots in which case the plant has to be completely harvested, including the roots. It will keep absorbing lead until the plant is harvested. Once this is done, the soil will have a lower level of the contaminant, but this has to be repeated through many harvesting seasons to achieve big results and a complete cleanup of the contaminated site. There are two forms of Phytoextraction; one type is natural hyper-accumulation, where plants naturally take up the contaminants in soil. The other form is by induced hyper-accumulation, where conditioning fluids containing chelators, or another element known as a mobilizing agent, is added to soil to increase metal solubility or mobilization in soil so that plants can absorb them much easily (Brookhaven National Laboratory, 2000). Usually after the process, the soil is fertile and can support vegetation (Brookhaven National Laboratory, 2000).

Few examples of Phytoextraction in today’s world are, Phytoextraction of lead using Indian Mustard, Ragweed or Hemp dogbane and Phytoextraction of arsenic from soil using the Sunflower (Helianthus Annuus) plant (U.S. Environmental Protection Agency, 2004). Advantages of Phytoextraction include: cheaper costs, less mass containing contaminant, and ease of implementation. Disadvantages like the plant taking too long to grow, or root systems not developing are present, but they can be overcome with planning and some attention. (Donald Bren School of Environmental Science & Management, 2002).

Bibliography

“An Overview of Phytoremediation of Lead and Mercury” June 6th 2000. The Hazardous Waste Clean-Up Information Web Site. Retrieved September 2nd 2005:

http://clu-in.org/download/studentpapers/henry.pdf

“Enhanced phytoextraction of arsenic from contaminated soil using sunflower” September 22nd 2004. U.S. Environmental Protection Agency. Retrieved September 2nd 2005:

http://www.epa.gov/superfund/programs/aml/tech/news/penhance.htm

“Getting the lead out”, June 1995. Vegetarian Times. Retrieved September 2nd 2005:

http://www.findarticles.com/p/articles/mi_m0820/is_n214/ai_16930491

“Phytoextraction”, February 2000. Brookhaven National Laboratory 2000. Retrieved July 29th 2005:

http://www.bnl.gov/erd/Peconic/Factsheet/Phytoextract.pdf

“Phytoextraction of Metals from Contaminated Soil” April 18th, 2001. M.M. Lasat Retrieved July 30th 2005:

http://www.engg.k-state.edu/HSRC/JHSR/vol2no5.pdf

“Phytoremediation” July 2002. Donald Bren School of Environment Science & Management. Retrieved September 2nd 2005:

“Phytoremediation” October 1997. Department of Civil Environmental Engineering. Retrieved August 2nd 2005:

http://www.ce.udel.edu/~sdkim/phytoremediation.htm

“Phytoremediation” June 2001, Todd Zynda. Retrieved August 1st 2005:

http://www.envirotools.org/factsheets/phytoremediation.shtml

“Phytoremediation of Lead in Residential Soils in Dorchester, MA” May, 2002. Amy Donovan Palmer, Boston Public Health Commission. Retrieved November 5th 2005:

http://dcc2.bumc.bu.edu/OTLT/EH807/powerpoints/lead/Slides%20Presentation.htm

“Technology Profile: Phytoextraction” 1997. Environmental Business Association. Retrieved August 4th 2005:

http://www.eba-nys.org/eba/971q/7phytote.html

“The role of EDTA in lead transport and accumulation by Indian mustard” June 1998. Entrez PubMed. Retrieved November 5th 2005:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9625697&dopt=Abstract