ESTCP Project #1011, Rhizosphere
Final Report
The Environmental Protection Agency1 and Interstate Technology and Regulatory Cooperation2
web sites provide recent reviews of phytoremediation.
For the situation that we addressed--petroleum compounds in near-surface soils--the generally
accepted mechanism is microbial degradation that is enhanced in the rhizosphere--the soil
immediately adjacent to and affected by plant roots.
1. Introduction
1.1 Background Information
This project included field demonstrations of rhizosphere-enhanced bioremediation of
petroleum, oils, and lubricants (POLs) at three cold-region locations. The demonstrations
evaluated the use of rhizosphere-enhanced remediation for treating POL-contaminated soils in
northern regions where low temperatures, site inaccessibility, permafrost, and freeze-thaw cycles
limit or, in many cases, prevent cost-effective application of traditional technologies and a
number of emerging innovative technologies. Rhizosphere-enhanced remediation may have
application and benefits at cold-region sites and Native American lands where former
Department of Defense (DoD) activities have impacted the soil.
widespread contaminants at many northern facilities owned, formerly owned, or formerly used
by the DoD. In cold regions, POLs and especially the polynuclear aromatic hydrocarbon fraction
(PAHs) are persistent in soils due to the low mean annual soil temperatures and the brevity of the
summer season. Some constituents in POLs are known human carcinogens.
Cleanup problems are compounded for sites that are in remote, inaccessible areas. The
Department of Defense has numerous sites in Alaska that were constructed during World War II
and expanded in the ensuing cold-war era where fuel was often transported and stored in 55-
gallon drums, resulting in POL releases. At many of these sites, mobilization and demobilization
costs are excessive. In some cases, ground transportation is possible only in winter, when the soil
is frozen. During the summer, when biotreatment would be feasible, air transportation must be
used, but landing sites cannot support larger aircraft. Construction supplies at many facilities
were delivered by air during the winter using packed-snow runways.
Many contaminated DoD sites are co-located with Native American population centers and serve
as hubs for transportation and communication. In some cases, DoD-related contamination is
located on Native American Lands and DoD has responsibilities to clean many of these sites. At
other cold-region sites, DoD lands are in caretaker status, awaiting turnover to Native American
1 http://www.epa.gov/ada/download/issue/epa_540_s01_500.pdf
2 http://www.itrcweb.org/common/content.asp?en=TA863827&sea=Yes&set=Both&sca=Yes&sct=Long
2
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