You are here:
DEVELOPING A FRAMEWORK FOR PERFORMANCE MONITORING TO ASSESS THE USE OF MONITORED NATURAL ATTENUATION FOR REMEDIATION OF INORGANIC CONTAMINANTS IN GROUND WATER
Citation:
FORD, R. G., R. T. WILKIN, R. W. PULS, R. WILHELM, AND K. LOVELACE. DEVELOPING A FRAMEWORK FOR PERFORMANCE MONITORING TO ASSESS THE USE OF MONITORED NATURAL ATTENUATION FOR REMEDIATION OF INORGANIC CONTAMINANTS IN GROUND WATER. Presented at 2005 American Geophysical Union Spring Meeting, New Orleans, LA, May 23 - 27, 2005.
Impact/Purpose:
To inform the public
Description:
The USEPA is leading an effort to develop technical documentation that provides the policy, scientific and technical framework for assessing the viability of MNA for inorganic contaminants in ground water (hereafter referred to as the Framework Document). Initial guidance on the application of MNA for all ground-water contaminants was first provided by the USEPA through the OSWER Directive, entitled 'Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites (9200.4-17P). The purpose of this Directive was to clarify USEPA policy regarding the use of MNA for remediation of contaminated soil and ground water. However, this publication is limited in scope with respect to providing detailed requirements for the technical assessment of inorganic contaminant MNA at hazardous waste sites. Development of the Framework Document is being carried out in conjunction with site-specific assessments of the viability of MNA at sites with ground water contamination. For one of these field sites, researchers at the National Risk Management Research Laboratory are assessing the potential for natural attenuation of arsenic within a contaminated ground-water aquifer. Based on the current state of knowledge, arsenic is considered to be a contaminant for which application of MNA may be of marginal success. The mobility of arsenic in ground water is strongly dependent on partitioning to immobile aquifer solids. However, arsenic is susceptible to changes in chemical speciation due to shifts in redox chemistry resulting from abiotic and biotic processes. These potential changes in chemical speciation require that detailed information for assessing the stability of immobilized arsenic be collected in space and time. This observation has been confirmed as part of the field study, where it has been established that partitioning to sediments results in significant removal of arsenic from the aqueous phase. However, the partitioning process is readily reversible under reducing conditions, indicating that MNA cannot be used as a sole remedy for site cleanup.