U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

For more information on Perchlorate, please contact:

Linda Fiedler
Technology Assessment Branch

PH: (703) 603-7194 | Email: fiedler.linda@epa.gov


Chemistry and Behavior

Perchlorate is composed of an oxygen tetrahedron with a chlorine atom at its center. The chlorine atom has an oxidation state of +7, which makes the molecule a strong oxidizing agent — hence its use as a rocket fuel. Mixtures of a chlorate, such as potassium chlorate, with charcoal or an easily oxidized organic substance such as sugar, react explosively when heated or in some circumstances rubbed together.

Despite its strength as an oxidizing agent, perchlorate has a high kinetic barrier that makes it slow to react under normal environmental conditions. Its general lack of reactivity and the proclivity of its salts to be soluble in water make it very mobile in the subsurface. While it is to some extent biodegradable in nature, it can form extensive plumes in groundwater. For example, there is a perchlorate plume from an Olin plant in California that is more than 10 miles long.

After a survey of drinking-water wells in western Texas showed perchlorate to be present in better than 80% of the wells tested over an area of 60,000 square miles, researchers at Texas Tech University analyzed the data and determined that rocket fuel, flares, fireworks, explosives, and Chilean fertilizer were unlikely to have been potential sources in some areas of the region. They arrived at a surprising conclusion: the evidence points to perchlorate being generated naturally in the atmosphere or by surface oxidation. The researchers theorize that natural perchlorate formation perhaps occurs by ozone and/or UV reactions with chloride in aerosols and in sands, possibly involving electrical discharge or lightning.


College Chemistry: A Systematic Approach.
H. Sisler, et al.
Macmillan Co., New York, 1964.

Adobe PDF LogoPerchlorate as an environmental contaminant.
E. Urbansky
Environmental Science & Pollution Research, 9(3) 187-192(2002)

Adobe PDF LogoTracing the origin of perchlorate
Britt A. Erickson
Analytical Chemistry, 388A-389A, 1 Nov 2004.

For Further Information

Atmospheric Processes May Create Perchlorate
Environmental Science and Technology, Science News, February 2, 2005.

Summary of a paper, "The Origin of Naturally Occurring Perchlorate: The Role of Atmospheric Processes," ES&T, 39(6) 1569-1575 (2005).

Adobe PDF LogoChemistry and Toxicology of Perchlorate
California Department of Toxic Substances Control, 15 pp, 2005

Adobe PDF LogoEcological Impact/Transport and Transformation of Perchlorate
Cornell Long, Ron Porter, Mark Sprenger, and Clarence Callahan.
Presented at the Perchlorate Stakeholders Forum, 19-21 May 1998, Henderson, NV

Adobe PDF LogoEnzymes responsible for chlorate reduction by Pseudomonas sp. are different from those used for perchlorate reduction by Azospira sp.
L. Steinberg, J. Trimble, and B.E. Logan. 2005
FEMS Microb. Lett. 247:153-159.

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
Jacimaria R. Batista, Penny S. Amy, Yi-Tung CHen, Lambis Papelis, and Richard Unz, Univ. of Nevada - Las Vegas.
U.S. EPA National Center for Environmental Research, EPA Grant Number R827622E03, 2001-2003.

Adobe PDF LogoField and Laboratory Evaluation of the Potential for Monitored Natural Attenuation of Perchlorate in Groundwater
Environmental Security Technology Certification Program (ESTCP), ER-0428, 107 pp, 2007

Samples were collected from 7 field sites to test innovative measures of enzyme activity for identifying microbial activity on perchlorate. Two lab studies were conducted: a 6-month biochemical oxygen demand study to measure the ambient oxygen demand of site-matrix ground water and microcosm treatability tests to measure the rate of perchlorate degradation under natural and enhanced conditions.

Perchlorate (Anaerobic) Degradation Pathway Map
Skikala Gajjala, University of Minnesota.
The University of Minnesota Biocatalysis/Biodegradation Database.

Adobe PDF LogoPerchlorate as an Environmental Contaminant
E. Urbansky
Environmental Science & Pollution Research 9(3) pp 187-192, 2002

A review article produced by the Office of Research and Development at the EPA National Risk Management Research Laboratory. This article provides a general overview of perchlorate environmental occurrence, toxicity, analytical chemistry, and remediative technologies. [This article is provided courtesy of ecomed publishers, ESPR - Environ Sci & Pollut Res 9 (3) 187-192 (2002). Please visit the ecomed Web site]

Adobe PDF LogoPerchlorate chemistry: Implications for analysis and remediation
E. Urbansky
CRC Press, 1998

This article presents a multitude of issues surrounding perchlorate. The article discusses sources and the nature of perchlorate contamination, physiological and health effects, chemical and physical properties, analytical chemistry, and remediation and treatment technologies. [This article is posted here with the permission of CRC Press LLC.]

Adobe PDF LogoPerchlorate Impacts to Private and Municipal Wells in Santa Clara County, CA
Thomas Mohr.
Technical Support Project Meeting, Sacramento, CA, 2004