- Program Areas
- Energy and Water
- Environmental Restoration
- Munitions Response
- Resource Conservation and Climate Change
- Weapons Systems and Platforms
Identification and Characterization of Natural Sources of Perchlorate
Perchlorate occurrence in groundwater has typically been linked to industrial releases and the historic use of Chilean nitrate fertilizers. However, recently a number of occurrences have been identified for which there is no obvious anthropogenic source. The possibility that perchlorate occurrence in surface and groundwater may have multiple origins (military, industrial, agricultural, or natural) complicates site characterization and efforts to assign responsibility for remediation and is an important factor in developing appropriate cleanup standards.
The objectives of this project are to determine the mechanisms responsible for natural perchlorate production, quantify the deposition from atmospheric sources, and assess the occurrence and describe the distribution of perchlorate in the environment.
Using a mix of new and established tools, researchers are investigating the occurrence, mechanisms of formation, and isotopic characteristics of natural perchlorate. Key elements of this project include (1) investigation of the role of chemical reaction mechanisms such as lightning discharges and energetic ultraviolet/ozone inputs with chloride-bearing water in the formation of perchlorate; (2) determination of accumulation mechanisms; (3) development of technologies to separate and purify minute amounts of perchlorate from complex matrices; (4) collection, analysis, and characterization of natural perchlorate samples; (5) accurate chlorine and oxygen isotopic analyses of perchlorate samples; (6) determination of key chemical and biological processes that influence isotopic signatures of perchlorate in natural samples; (7) determination of the geologic, hydrologic, and climatic conditions under which natural perchlorate may be expected to form and be preserved in the environment; and (8) evaluation of the concentrations and mechanisms of perchlorate accumulation in plants.
This project is providing the Department of Defense and scientific community with the boundary conditions of natural perchlorate production, accumulation, and occurrence. In addition, it is providing the fundamental understanding and analytical tools necessary to differentiate natural from anthropogenic sources of perchlorate, as well as to predict where natural perchlorate will most likely be found under various geological and climatic conditions, greatly aiding forensic investigations of perchlorate in the environment. (Anticipated Project Completion - 2012)
This research shows that perchlorate (ClO4-) is produced in the atmosphere likely from reactions of Cl- or ClOx with O3 and perhaps with ultraviolet radiation. These reactions have been extensively evaluated, including the impact of reactant concentration, reaction rates, and distribution of final products. This information has important implications for both atmospheric chemistry as well as numerous oxidation processes involved in water treatment and industrial applications. The project data clearly indicate that deposition of perchlorate is ubiquitous across North America and apparently the world. This relatively unexplored source may help to explain the growing reports of perchlorate in produce, milk, and other food items and should be considered when evaluating overall source contributions or drinking water standards. Significant progress has also been made in characterizing the stable isotope signatures of Cl and O in natural perchlorate and the occurrence of the long-lived radioactive isotope 36Cl in natural perchlorate. The current data indicate that natural perchlorate indigenous to the southwestern United States has at least two unique stable isotope signatures (when considering δ18O, δ17O, and δ37Cl together) and that much of this material has elevated 36Cl, suggesting formation in the stratosphere. Based on isotopic composition, natural perchlorate indigenous to the United States can be distinguished from both synthetic perchlorate and perchlorate derived from Chilean fertilizers.
Points of Contact
Dr. Gregory Harvey
U.S. Air Force
Phone: 937-938-3291 x302
Dr. Paul Hatzinger
CB&I Federal Services
SERDP and ESTCP
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
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