Samples of groundwater in and around Lake County have been shown to have lead levels as high as 8 ppm as a result of your water analysis. These concentrations are well above the EPA action level of 0.015 ppm. Analysis of residential soils has found levels there to be as high as 1000 ppm; therefore, the EPA has begun evaluating the site for remediation.

There are two major categories of remediation for “heavy” metals such as lead. One method requires the physical movement of contaminated soil to a treatment facility and subsequent transfer of “clean” soil to the affected area. The second method involves phytoremediation, the removal of toxic substances by living plants. Because funding is limited, this second method has been chosen.

The following are four types of phytoremediation: phytoaccumulation, phytodegradation, rhizodegradation, and phytovolatization. Research indicates that phytoaccumulation is ideally suited for the Lake County site.

You are a member of the EPA’s Superfund Response Team. You and your team must now decide on the most effective way to implement phytoaccumulation in the Lake County area. As part of your research, you should access the following websites in order to answer the questions below:

A Resource Guide: The Phytoremediation of Lead in Urban, Residential Soils, Joseph L. Fiegl, et al., Northwestern University.

http://www.civil.northwestern.edu/ehe/html_kag/kimweb/MEOP/Index.htm

Phytoremediation, by Kelly E. Belz, 1997, in Groundwater Pollution Primer, Virginia Polytechnic Institute and State University.

http://www.cee.vt.edu/ewr/environmental/teach/gwprimer/phyto/phyto.html

Questions

1. Give comparative costs for the two major types of remediation discussed in paragraph two above—i.e., (a) removal and replacement of contaminated soils or (b) phytoremediation.
2. Why are heavy metals, such as lead, difficult to remove using phytoremediation?
3. Explain the process of each of the four types of phytoremediation: phytoaccumulation, phytodegradation, rhizodegradation, and phytovolatization.
4. Which of the four processes described in question 3 is the best choice for the clean-up of lead at the Lake County site (i.e., why might the other three techniques not be as effective)?
5. What is a hyperaccumulator?
6. Give at least two ways in which the uptake of lead though phytoaccumulation can be enhanced.
7. What plant(s) might be the best choice for phytoremediation at the Lake County site?

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