Natural Attenuation

Several organizations have developed definitions for natural attenuation.

The U.S. Environmental Protection Agency defines monitored natural attenuation as the

"reliance on natural attenuation processes (within the context of a carefully controlled and monitored site cleanup approach) to achieve site-specific remediation objectives within a time frame that is reasonable compared to that offered by other more active methods. The 'natural attenuation processes' that are at work in such a remediation approach include a variety of physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater. These in-situ processes include biodegradation; dispersion; dilution; sorption; volatilization; radioactive decay; and chemical or biological stabilization, transformation, or destruction of contaminants." (EPA, OSWER Directive 9200.4-17P)

The American Society for Testing and Materials (ASTM) defines natural attenuation as the

"reduction in mass or concentration of a compound in groundwater over time or distance from the source of constituents of concern due to naturally occurring physical, chemical, and biological processes, such as; biodegradation, dispersion, dilution, adsorption, and volatilization." (ASTM, E1943-98)

The U.S. Air Force Center for Environmental Excellence defines natural attenuation as the processes resulting

"from the integration of several subsurface attenuation mechanisms that are classified as either destructive or nondestructive. Biodegradation is the most important destructive attenuation mechanism. Nondestructive attenuation mechanisms include sorption, dispersion, dilution from recharge, and volatilization." (Wiedemeier, 1999)

The U.S. Army defines natural attenuation as

"the reduction of contaminant concentrations in the environment through biological processes (aerobic and anaerobic biodegradation, plant and animal uptake), physical phenomena (advection, dispersion, dilution, diffusion, volatilization, sorption/desorption), and chemical reactions (ion exchange, complexation, abiotic transformation). Terms such as intrinsic remediation or bio-transformation are included within the more general natural attenuation definition." (U.S. Army, 1995)

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• A Unique Approach to Evaluating Natural Attenuation is Applied Worldwide
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USGS Information on Natural Attenuation

• Topical Information on Natural Attenuation, Toxic Substances Hydrology Program
• Listing of Toxics Program Natural Attenuation Remediation Related Activities
• Listing of Other USGS Natural Attenuation Remediation Related Activities
• Natural Attenuation Strategy for Groundwater Cleanup Focuses on Demonstrating Cause and Effect: Bekins and others, 2001: EOS
• Bioremediation--Nature's Way to a Cleaner Environment: USGS Fact Sheet FS-054-95.
• Bibliography on Natural Attenuation and Biodegradation, Toxics Program

Other Information on Natural Attenuation

• Natural Attenuation for Groundwater Remediation, 2000: National Academies Press
• In Situ Bioremediation: When Does it Work?,1993: National Academies Press
• U.S. Environmental Protection Agency
  • Technology Focus: Natural Attenuation, Clu-In, Technology Innovation Office
  • A Citizen's Guide to Natural Attenuation, Clu-In, Technology Innovation Office
  • Monitored Natural Attenuation: It's Much More Than Watching The Grass Grow!, Office of Underground Storage Tanks
  • Issues Associated With Natural Attenuation, Office of Underground Storage Tanks
  • Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water: Office of Research and Development, EPA/600/R-98/128
• Technical Guidance for the Long-Term Monitoring of Natural Attenuation Remedies at Department of Energy Sites
• Natural Attenuation Of Organic Compounds, Center for Public Environmental Oversight, San Francisco State University

References

• ASTM International, 2003, E1943-98 Standard guide for remediation of ground water by natural attenuation at petroleum release sites: ASTM Book of Standards, v. 11.04, 43 p.
• U.S. Army, 1995, Interim army policy on natural attenuation for environmental restoration: Washington, DC, Department of the Army, Assistant Chief of Staff for Installation Management, DAIM-ED-R (200-1c), September 12, 1995.
• U.S. Environmental Protection Agency, 1999, OSWER Directive 9200.4-17P -- Use of monitored natural attenuation at Superfund, RCRA corrective action, and underground storage tank sites -- April 21, 1999: Office of Solid Waste and Emergency Response, 41 p.
• Wiedemeier, T.H., Wilson, J.T., Kampbell, D.H., Miller, R.N. and Hansen, J.E., 1999, Technical protocol for implementing intrinsic remediation with long-term monitoring for natural attenuation of fuel contamination dissolved in groundwater: U.S. Air Force Center for Environmental Excellence, v. 1 & 2, A324248, A324247a, A324247b.

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