Research Capabilities
Monitored Natural Attenuation
Contaminants in the environment are subject to a variety of physical, chemical, or biological processes that lead to their attenuation. The U.S. Environmental Protection Agency (EPA) recognizes that this natural attenuation can be used as a remedy if certain criteria are met; namely, the attenuating mechanisms can be shown to offset the contaminant loading (see figure). In EPA Office of Solid Waste and Emergency Response (OSWER) Directive 9200.4-17, the natural attenuation processes have been defined as follows:
...a variety of physical, chemical, or biological processes that under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume, or concentrations 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."
To demonstrate that monitored natural attenuation is a viable remediation option, the physical, chemical and biological processes and the rate and extent to which these natural processes attenuate (i.e., decrease) the mass, toxicity, mobility, volume, or concentration must be demonstrated for the contaminants of interest under site-specific conditions.
Characterization of these complex processes is inherently an interdisciplinary problem. Researchers at PNNL are uniquely equipped with the necessary interdisciplinary expertise, facilities and tools to conduct the required studies to complete these characterization tasks. PNNL staff have highly sophisticated experimental and analytical laboratories, modeling capabilities and decision-making tools, which places PNNL in an exceptional position to conduct detailed investigations for identifying and quantifying the natural attenuation of contaminants in the environment.