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The Fate and Transport of Perchlorate in a Contaminated Site in the Las Vegas Valley. Part A: Investigation of the Influence of Biological Degradation and Sorption on the Fate of Perchlorate. Part B: Modeling of the Transport of Perchlorate in the Las Vegas Wash.EPA Grant Number: R827622E03
Title: The Fate and Transport of Perchlorate in a Contaminated Site in the Las Vegas Valley. Part A: Investigation of the Influence of Biological Degradation and Sorption on the Fate of Perchlorate. Part B: Modeling of the Transport of Perchlorate in the Las Vegas Wash.
Investigators: Batista, Jacimaria R. , Amy, Penny S. , James, David S. , Luke, Barbara , Papelis, Lambis , Pepper, Darrell
Current Investigators: Batista, Jacimaria R. , Amy, Penny S. , Chen, Yi-Tung , Papelis, Lambis , Unz, Richard
Institution: University of Nevada - Las Vegas
EPA Project Officer: Winner, Darrell
Project Period: August 9, 1999 through August 8, 2003
Project Amount: $158,502
RFA: EPSCoR (Experimental Program to Stimulate Competitive Research) (1998) RFA Text | Recipients Lists
Research Category: EPSCoR (The Experimental Program to Stimulate Competitive Research)
The recent discovery of perchlorate (ClO4-), an important component in rocket fuel and explosives, in the water supplies in California, Nevada and Utah has generated considerable interest in the fate and transport, health effects and potential treatment technologies to remove the contaminant from water supplies. A site in Las Vegas, Nevada is highly affected and contaminated groundwater has seeped to Lake Mead and the Colorado River, the water supply to millions of people in Nevada, California and Arizona. Very little is known about the specific interactions of perchlorate with various environmental components (e.g., soil, microbes). To date, research on the interaction of perchlorate with soils and indigenous microorganisms has not been conducted. There is, therefore, a substantial need to assess the extent of perchlorate interaction with various environmental components, and their effect on the migration of perchlorate in the subsurface. The contaminated Las Vegas Valley site, located approximately 15 miles from the UNLV campus is an ideal site for such a study.
The objectives of the proposed research are (1) To investigate the role of indigenous microbial communities on the biodegradation of perchlorate in the contaminated Las Vegas Valley site. The goal is to evaluate whether indigenous bacteria have acquired the genes, after being exposed to perchlorate, to code for the enzymes which would reduce this contaminant to nontoxic chloride.
The hypothesis will be tested by incubating soil and water samples from the contaminated Las Vegas site and monitoring perchlorate biodegradability. Biodegradability will be assessed by measuring decrease in perchlorate concentration, increase in end-products (chloride) and increase in microbial activity (cell counts). (2) To evaluate the influence of sorption on the fate of perchlorate. Although perchlorate has been termed the perfect conservative tracer, this hypothesis has not yet been tested in contaminated soils. This hypothesis will be evaluated by performing column adsorption experiments using local soils to assess the partitioning of perchlorate between water and soils. A complete characterization of the soil samples using x-ray diffraction, and electron microscopy will be performed. (3) To evaluate the potential of chemical (abiotic) reduction of perchlorate to chloride using several reducing agents. Thermodynamically, the reaction of perchlorate with iron and manganese results in very high negative free energy changes indicating extremely favorable reaction. The possibility of these reactions occurring will be examined by adding layers of iron and manganese to columns filled with soils from the Las Vegas Valley. (4) To model the transport of perchlorate from the pollution source to the Las Vegas Wash site using GWADAPT, a code written in C/C++. Perchlorate concentration from sixty wells located near the pollution source site will be assessed. This data will be combined with a pre-existing model of the groundwater flow in the Valley, and with physical properties (e.g., hydraulic conductivity, aquifer thickness) to predict the migration of perchlorate in the site.
This research will generate data on the interactions of indigenous microorganisms and soils with perchlorate. The results generated will furnish information on the fate of perchlorate in the subsurface and will provide insight into the factors controlling perchlorate migration to water supplies. Because perchlorate is known to interfere with the functioning of the thyroid glands in humans, data on its fate and transport, such as the data generated by the proposed research, can be used in decision making regarding remediation of perchlorate contaminated areas and the assessment of the risk associated with consumption of perchlorate-containing waters.