ABSTRACT
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3.1 INTRODUCTION
The term monitored natural attenuation (MNA) refers to an approach to clean up subsurface contamination, specifically in groundwater, by relying on natural processes and monitoring. MNA is also referred to as
natural degradation
and
intrinsic
or
passive remediation
. Natural attenuation processes include a variety of physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume, and concentration of contaminants in groundwater. Depending on the geologic conditions, types of contaminants, and contaminant mass and distribution at a given contaminated site, MNA could emerge as the preferred choice of remediation approach. Natural attenuation relies on the
assimilative capacity
of the ecosystem for the reduction of contaminant concentration and mass. This approach has been utilized by environmental engineers for a long time to control industrial and municipal wastewater discharges into surface waterbodies and maintain acceptable water quality standards.
