Grantee Research Project Results
2004 Progress Report: Phytoremediation of Perchlorate and N-nitrosodimethylamine as Single and Co-contaminants
EPA Grant Number: R831090Title: Phytoremediation of Perchlorate and N-nitrosodimethylamine as Single and Co-contaminants
Investigators: Mbuya, Odemari S. , Nzengung, Valentine A. , Ugochukwu, Ngozi H. , Jain, Amita
Institution: Florida Agricultural and Mechanical University , University of Georgia
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 2003 through September 30, 2005
Project Period Covered by this Report: October 1, 2003 through September 30, 2004
Project Amount: $399,875
RFA: Superfund Minority Institutions Program: Hazardous Substance Research (2002) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals
Objective:
Phytoremediation is being considered for addressing perchlorate contamination at a number of sites. Although investigators have shown that perchlorate is taken up and slowly phytodegraded in short-term laboratory studies lasting a few weeks, the lingering concern over the recycling of perchlorate taken up into plant leaves especially during senescence in the fall season remains unanswered. In this project, this question will be answered by conducting long-term studies, lasting the entire growth cycle, with plants growing under natural field conditions and controlled pot experiments.
The specific objectives of this research project are to:
- determine the long-term fate of perchlorate taken up into plants (i.e., the change in concentration of perchlorate in plant leaves prior to and after senescence);
- develop a process to minimize uptake and phytodegradation of perchlorate while enhancing root-zone biodegradation (rhizodegradation) reactions;
- and develop an analytical method for N-nitrosodimethylamine (NDMA), a byproduct of 1,1-dimethylhydrazine used in liquid rocket fuel production.
Currently, there is neither U.S. Environmental Protection Agency nor peer-reviewed methods for the analysis of NDMA and its metabolites in plant tissues.
Progress Summary:
Uptake and phytodegradation of perchlorate and NDMA were evaluated on plants growing under natural field conditions, in hydroponic bioreactors, and in soil contained in pots. A breakthrough was found over the past 12 months on biostimulation and enhancement of rhizodegradation of perchlorate. The root-zone environment was manipulated using suitable dissolved organic carbon (DOC) sources to reduce the lag time and enhance rapid rhizodegradation of perchlorate to chloride. Bioreactors planted with cuttings of willow were amended with 500 mg/L DOC from mushroom compost extract, chicken litter, and acetate. Initial perchlorate concentrations of 25 and 40 mg/L were degraded to below the Ion Chromatography method detection limit of 2 μg/L in less than 10 days. The average rate of perchlorate removal from the DOC-amended rhizosphere bioreactor was calculated as 7.0 mg/L/day compared to 0.25 mg/L/day for unamended controls. No biodegradation of perchlorate was observed in the control treatments (no plant) consisting of the nutrient solution plus sterilized mushroom compost and acetate. Complete degradation was achieved in 15 days in bioreactors supplied with unsterilized chicken litter extract and no plant. The benefit of reducing the lag time and enhancing rhizodegradation is to the increase in the rate of phytoremediation, which has the ability to minimize the undesirable uptake of perchlorate fraction into plant tissues and the potential for recycling of perchlorate to soil and water. Ongoing research focuses on biostimulation and enhancement of rhizodegradation of NDMA.
Different species of field plants (e.g., willow, tamarix, cat tail, sweet gum, pine, and sedge) growing over perchlorate-contaminated soils and groundwater were collected in Texas and Nevada and analyzed for perchlorate. Willow plant tissues collected from plants growing on or near in situ bioremediated soils contained less than 10 mg/kg perchlorate dry weight. Data from one growing season suggest that tamarix growing on perchlorate-contaminated soil at the Las Vegas Wash takes up, accumulates, and releases perchlorate to surface soils when the plants senesce during fall months. The highest concentration of perchlorate was measured in dead leaves (296 mg/kg) that had fallen off of the tamarix plants and trunk tissues (463 mg/kg). The recycling of perchlorate by tamarix plants explained the presence of high concentrations of perchlorate in the top soils. There is not sufficient evidence to conclude at this time that willows, sweet gum, pine trees, and the wetland plants monitored could recycle perchlorate.
Willow (Salix babylonica) plants were grown in 40 L plastic pots filled with sandy loam soil dosed with either 100 mg/kg sodium perchlorate, 1 mg/kgNDMA, or 100:1 mg/kg of a perchlorate:NDMA mixture for an entire year. The plants were frequently irrigated and fertilized with 210 kg N/ha in form of Miracle-Gro. Senesced leaves were collected throughout the year and stored in a deep freezer. The senesced leaves will be analyzed for perchlorate, NDMA, and metabolites content at the end of the year.
Future Activities:
We will conduct two rounds each of plant tissues sampling at the Longhorn Army Ammunition Plant in Karnack, Texas, and the Las Vegas Wash in Henderson County, Nevada. We will complete development of an analytical method for NDMA and its phytodegradation products, including an acceptable quality assurance/quality control, and publish the method. In addition, we plan to conduct phytoremediation experiments with NDMA and NDMA mixed with perchlorate. We will evaluate the effect of concentration and rhizodegradation on the uptake of perchlorate in willow and cottonwood plants under hydroponics condition. Three treatments will be used: 100, 50, and 25 mg/L. Two sets of experiments will be conducted; one under sterile and the other under nonsterile conditions for a total of 60 days.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 12 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Yifru D.D, and V.A. Nzengung. Enhancement of rhizodegradation of perchlorate (ClO 4 -) using artificial and natural carbon and electron sources. Journal of Environmental Science and Technology (submitted, 2004). |
R831090 (2004) |
not available |
Supplemental Keywords:
tamarix, salt cedar, phytodegradation, rhizodegradation, plant tissues, senescence, biostimulation, cottonwood, phytoaccumulation, bioreactors, radiolabeled, willows, analytical chemistry, bioremediation, contaminated sediments, environmental microbiology, hazardous waste, microbiology, molecular biology/genetics, n-nitrosodimethylamine, superfund site remediation, bioavailability, biochemistry, biodegradation, contaminated sediment, contaminated soil, degradation, industrial waste, microbial degradation, perchlorate, phytoremediation,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Contaminated Sediments, Environmental Microbiology, Hazardous Waste, Bioremediation, Hazardous, microbiology, degradation, Superfund site remediation, plant species, industrial waste, microbial degradation, bioavailability, biodegradation, perchlorate, contaminated sediment, contaminated soil, contaminants in soil, bioremediation of soils, N-Nitrosodimethylamine, biochemistry, phytoremediationProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.