Toxic Substances Hydrology Program
Monitored Natural Attenuation - "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." - U.S. Environmental Protection Agency, 1999
Natural Attenuation - "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." - American Society for Testing and Materials, 2003
Natural Attenuation - [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." - U.S. Air Force Center for Environmental Excellence, 1999
Natural Attenuation - "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
Text in brackets ("[text]") are additions by the editor
USGS Information on Natural Attenuation
Other Information on Natural Attenuation
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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