Introduction to Phytoremediation - CLU-IN

ing such concerns, it is important to compare the relative
ecological risks posed by phytoremediation to those risks
already occurring on site or those risks posed by alternative
cleanup methods. Actions needed to protect ecosystems
should be clearly specified in the site cleanup plan.
Overall ecological risks associated with remediation of
a site are often overlooked, even by interested parties who
may be familiar with the human health and ecological risks
associated with current site conditions or with the general
risks posed by feasible alternative cleanup methods. These
overall ecological concerns may be expressed in a limited
context that does not help in the selection of an alternative.
Often, however, a site visit will broaden the understanding
of interested parties and thus enable them to better
assist in identifying options with the greatest overall ecological
benefits.
Listed below are issues that typically arise in such discussions.
Also included are frequently overlooked factors
that should be considered in identifying the relative risks.
2.5.1 Introduction of Non-Native Plants
History is rife with disastrous examples of newly introduced
plant species spreading quickly to damage native
ecosystems (e.g., kudzu, Eurasian watermilfoil, etc.). Plants
that work best in remediating a particular contaminant may
or may not be native to a particular area. Although native
plants are most desirable, non-native species may be acceptable
under the following circumstances:
• The plants have been previously introduced, and are
now so common that their proposed use would not
create a new ecological risk.
• The plants are unable to propagate effectively in the
wild (e.g., sterility, dependence on human cultivation,
etc.).
• Genetically altered plants have been introduced. Mankind
has been using selective breeding to obtain desired
plant characteristics for at least 10,000 years.
Now, researchers in many fields are using new genetic
engineering techniques to replace selective breeding,
allowing them to achieve their desired results more
quickly and selectively. Decisions on the desirability of
using genetically engineered plants must be site specific.
2.5.2 Integration of Phytoremediation
Into the Site’s Long-Term
Landscaping Objectives
Long-term phytoremediation-based treatment can be designed
into future site landscaping plans, e.g., tree borders
used for shading and visual screening can also provide ongoing
groundwater remediation, etc. Such vegetation can
often create valuable ecological niches, particularly in urban
industrial areas.
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Public Uses
A number of contaminated sites are being converted to
parks and other low-intensity public uses. These sites,
particularly with their greater flexibility in the timing and
design of cleanup, frequently offer significant ecological
opportunities. Trees and shrubs do not have to be planted
in straight rows to be effective in remediation.
Commercial Uses
Businesses traditionally landscape for aesthetic reasons
and storm run-off control. These functions may be combined
with phytoremediation to offer significant opportunities.
Properly designed and located, such landscaping could
also provide long-term treatment and enhanced ecological
habitats. A site owner may be willing to significantly
expand the land committed to phytoremediative landscaping
if that commitment would reduce overall cleanup costs
and allow quicker site redevelopment. A phased approach,
with intensive short-term treatment by one plant species
followed by permanent plantings with more beneficial vegetation,
may maximize ecosystem benefits.
Wood Lot Uses
Short-rotation woody crops for pulp, fuel, or timber may
be grown on land with nonaccumulating organic contaminants.
The trees could be grown and harvested while recalcitrant
compounds slowly degrade.
2.5.3 Phytoremediation as an Interim
Solution
Phytoremediation is most suitable for remediating sites
or portions of sites with widespread, low-mid level contaminants
that are often too expensive to remediate by
traditional means. Absent a cost-effective remediation
method, contaminants are often left in place, and contact
with the waste attempted to be minimized by fences, institutional
controls and deed restrictions. Too often no one is
required or able to cleanup the site, and many sites have
been abandoned with no clean up or controls. Occasionally
a phytoremediation system may be inexpensive enough
that it could be installed during considerations and debate
regarding a permanent solution, and removed once a final
remedy is implemented. The interim ecosystem benefits,
coupled with improved aesthetics, and some containment
and/or degradation may combine to make even temporary
revegetation worthwhile.
Although phytoremediation may not be the selected final
technique, the benefits of a well-designed, properly installed,
and capably managed phytoremediation system
may be preferable to the risks posed by leaving a waste
site completely untreated during delays in implementing a
final remedy.
2.5.4 Ecosystem Restoration at
Phytoremediation Sites
Many sites with contamination support complex ecosystems,
primarily due to the low level of human activity on the