Technology:
Phytoremediation
- Greenhouse experiments were performed using contaminated soil and clean sand
- Three candidate plant species were tested: Prairie Cascade hybrid willow; canola; and kochia
- For the soil experiment, the soil was spiked with EDTA and citric acid
- For the sand experiment, the soil was spiked with metals (soluble forms of Cr, Zn, Hg, Ag, and Se)
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Cleanup Authority:
CERCLA - ROD dated 9/29/98
Site Contact:
Scott D. Lee
Argonne National Laboratory - West
P.O. Box 2058
Idaho Falls, ID 83403-2528
Telephone: (208) 533-7829 | Regulatory Authority:
Not Identified |
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Contaminants:
Heavy metals
- Contaminants of concern included chromium, mercury, selenium, silver, and zinc.
- Soil concentrations are 44.85 mg/kg Cr, <1.5 mg/kg total Hg, and 56.32 mg/kg total Zn |
Waste Source:
Scientific and engineering research activities |
Type/Quantity of Media Treated:
Soil
- Site is a relatively flat, semi-arid, sagebrush desert
- Climate conditions are a temperature range of 7.9 F - 84.8 F; a growing season of April to mid-October; and annual average precipitation of 8.7 inches
- Soil texture is loam, with particle size distribution of 47% sand, 34.6% silt, 18.4% clay
- Soil composition is 1.59% organic matter, 5.41% lime, 5,310 mg/kg extractable Ca, 510 mg/kg extractable Mg, 76 mg/kg extractable Na, 438 mg/kg extractable K, 48 mg/kg extractable P, 71 mg/kg soluble SO4, and 76 mg/kg soluble Na; soil pH is 8.57 |
Purpose/Significance of Application:
Bench-scale testing of phytoremediation to treat heavy metals in soil |
Regulatory Requirements/Cleanup Goals:
For bench-scale tests:
- Determine uptake rates and metal concentration factors for each plant species
- Determine the most effective, non-hazardous chelating agent to increase the availability of metals from impacted soils
- Evaluate potential maximum uptake of metals by candidate plant species under selected conditions |
Results:
- The optimum formulation of chelating agents for treating the metals was determined to be a 0.05 molar solution of 40% EDTA and 60% citric acid
- In the sand experiment, the best recovery levels for zinc, chromium, mercury, and silver were found in the willow with 96%, 38%, 42%, and 24% recovery, respectively
- Testing using actual soils yielded significantly lower removals than with the sand experiment; the amount of zinc and chromium removed was 4-5% and 2%, respectively
- The willow roots had better removal of the metals than either kochia or canola
- It was concluded that willows would be used in the field; possible removal rates of up to 14% of Zn and 3 to 4% Cr per year were predicted, which could result in cleanup times between 6 - 7 years for Zn and 9 years for Cr |
Cost Factors:
- Use of phytoremediation at full-scale for four sites at ANL-W was projected to cost $2,247,000
- This consisted of management - $528,000; documentation - $98,000; construction - $841,000; and O&M - $780,000
- The construction cost consisted of an initial 2-year field test at $300,000 and a contingency of $542,000 for five additional years of phytoremediation |
Description:
The Idaho National Engineering and Environmental Laboratory (INEEL), located in Idaho Falls, Idaho, is a government facility managed by the U.S. DOE. Various sites at ANL-W are contaminated with wastes generated from the scientific and engineering research at ANL-W and contain various levels of petroleum products, acids, bases, PCBs, radionuclides, and heavy metals. The ROD for Waste Area Group 9 identifies seven areas that will undergo remediation and identifies phytoremediation as the remedy, with a contingent remedy of excavation and disposal. As a pre-condition for implementing phytoremediation in these areas, bench scale (laboratory and greenhouse) tests were performed to evaluate the applicability of phytoremediation as well as to determine operating parameters and time frames for full-scale implementation
The bench-scale tests were conducted in a greenhouse using contaminated soil and sand that was spiked with metals. Results from these tests showed that use of contaminated soils yielded significantly lower removals than sand, with removals from soil of chromium - 2% and zinc - 4 to 5%, and that willows were the best species for use at the site. Based on these results, ANL-W calculated the number of years of phytoremediation that would be required to meet the remediation goals for several site areas, and these estimates ranged from 6 to 122 years. As a next step, each of five sites at ANL-W will be treated using phytoremediation during a two-year field test. Each site will be planted with three-foot tall bare-root willow trees in a grid pattern, and whole tree harvesting (roots and above ground) will occur at the end of each growing season. Excavated trees will be chipped and transported to an on-site incineration facility for disposal. |
