1.2 Objectives of the Demonstration
The objective of this rhizosphere-enhanced remediation demonstration was to treat POL-
contaminated soils in northern regions where low temperatures, site inaccessibility, and freeze-
thaw cycles limit or prevent cost-effective application of either traditional technologies or
emerging innovative technologies. We demonstrated the ability of cold-tolerant plants, nutrient
additions, and their combination to remediate POL-contaminated soils at our three
geographically diverse sites in Alaska. We documented seeding, monitoring, and site-specific
conditions for each location under which the technology was applied. We evaluated the
technology in terms of its overall cost, regulatory acceptance, and the practicality of
implementation. We successfully demonstrated that rhizosphere-enhanced remediation can
produce measurable changes in petroleum concentrations
1.3 Regulatory Drivers
This project addressed cleanup and restoration of contaminated soils resulting from DoD
activities on Native American lands. It also addressed cleanup requirements developed by user
groups within DoD for (1.3.b) On-Site Treatment of Organics Contaminated Soils and (1.3.m)
Soil Bioremediation. Native American Communities and a Native American owned small
businesses, ClearWater Environmental Services, Incorporated, were partners in the
demonstrations at the Annette Island and Campion sites. At Annette Island, we coordinated
closely with the Metlakatla Indian Community, and they were active partners in site selection.
We sought assistance from Ilisagvik College in Barrow, Alaska, but were unable to develop an
active partnership.
1.4 Demonstration Results
Using depletion data that were normalized to both a biomarker and local temperatures--
expressed as growing degree-days (GDD)--we demonstrated statistically significant plant
effects for specific petroleum fractions. Effects were not uniform for all petroleum fractions, and
plants had a greater impact on heavier fractions. These data agree with recent findings that root
exudates can provide an analog enrichment effect. We also showed inhibition of depletion of
specific petroleum fractions that was related to fertilizer additions without plants. Characterizing
the culturable microbial communities suggested that bacterial and fungal populations responded
to fertilizer and plant effects, respectively. These findings agree with our findings at other field
locations. Our field data also highlighted some of the difficulties in showing treatment progress
in surface soils in cold regions. These results also can be used to better understand other surface-
soil contamination issues, and their low-cost, wide-scale treatment.
1.5 Stakeholder / End User Issues
These data are useful in showing that rhizosphere-enhanced remediation has a measurable and
significant impact on treating petroleum-contaminated surface soils using low-cost methods that
require minimal maintenance and can be used over large areas. Importantly, they also
demonstrate that commonly employed monitoring methods will be insufficient for detecting
changes in the contaminant concentrations in surface soils undergoing plant-based treatment. The
benefits of these findings are that this plant-based approach does have a positive effect for
treating surface soils, and that monitoring methods will need to be adjusted to successfully
observe these changes.
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