Phytoremediation of Perchlorate and N-nitrosodimethylamine as Single and Co-contaminantsEPA Grant Number: R831090
Title: Phytoremediation of Perchlorate and N-nitrosodimethylamine as Single and Co-contaminants
Investigators: Mbuya, Odemari S. , Jain, Amita , Nzengung, Valentine A. , Ugochukwu, Ngozi H.
Institution: Florida Agricultural and Mechanical University
Current Institution: Florida Agricultural and Mechanical University , University of Georgia
EPA Project Officer: Carleton, James N
Project Period: October 1, 2003 through September 30, 2005
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
Although potential plant species suitable for phytoremediation of perchlorate and the phytoprocesses involved (rhizodegradation and phytodegradation) have been identified in previous research, regulators and some critics argue that plants recycle the perchlorate fraction taken up into the plant. There is no published work to date on phytoremediation of N-nitrosodimethylamine (NDMA). The proposed studies will include laboratory, greenhouse and field components. Test plants for the phytoremediation of perchlorate and NDMA will be willow (Salix nigra) and eastern cottonwood (Populus deltoides).
Specific objectives of the project are to: 1) determine the fate of perchlorate taken up into plants and after senescence; 2) evaluate the feasibility of using plants to degrade NDMA; 3) identify the transformation pathways and mechanisms of phytoremediation of NDMA; 4) establish whether woody plants selectively take up perchlorate or NDMA when they occur as co-contaminants; and 5) determine the role of nitrate during phytoremediation of NDMA.
Willow (Salix nigra) and eastern cottonwood (Populus deltoides) will be used in this study. Experiments on uptake and transformation rates of NDMA will be conducted in hydroponic reactors. The uptake and transformation rate will be measured by extracting 5 mL of solution for analysis once every 24 hours. The withdrawn samples will be filtered with a 0.45 micron filter before analysis by HPLC, GC/MS and LC/MS/MS. Sand and soil bioreactor experiments will be conducted in 5 gallon buckets filled with either acid washed silica play sand or soil from a perchlorate and NDMA contaminated site. Each sand bioreactor will contain the same mass of sand, volume of water, concentration of nutrient, and dosed to the same initial NDMA concentration as in the contaminated soil. Test plants of approximately the same biomass will be transplanted in each bioreactor. The level of water in each bioreactor will be kept constant by replenishing evapotranspired water multiple times daily. Different types of controls will be prepared and handled in parallel to quantify losses due to sorption and biodegradation. The bioreactors will be maintained at ambient temperature under natural light in a greenhouse. Similar experiments will be conducted using radiolabeled perchlorate and NDMA as co-contaminants. Phyto-transformation products and mass balance of NDMA using willow and cottonwood will be determined in specially designed experiments to obtain quantitative data on the distribution of metabolites and the parent compound between the solution phase and the plant matter. Liquid scintillation procedures will be used to quantify the amount of polar fraction of metabolites in comparison to the total 14C-NDMA activity. A biological tissue oxidizer will be used to quantify the irreversibly bound fraction. GC/MS and LC/MS/MS analytical techniques will be used to identify metabolites of unlabeled NDMA in the root zone solution and plant extract.
The laboratory and field data collected during this study should reveal the fate of perchlorate taken up into plants used for phytoremediation and whether concerns on the likelihood that a fraction of the perchlorate taken up by plants will be recycled back into soils is warranted. The successful completion of this study should indicate that phytoremediation is a potentially effective technology for the cleanup of perchlorate and NDMA at some Superfund sites where both compounds have been identified. Perchlorate and NDMA are among some the very toxic emerging group of environmental contaminants.