Mobility of Particulate and Dissolved Munitions Constituents in the Vadose Zone at Operational Ranges
ER-1690
Objective
Munition constituents (MC) are heterogeneously distributed at shallow depths in the soils of operational ranges as a result of low-order (incomplete) detonations. Dissolved explosive compounds have found their way into groundwater aquifers underlying various Department of Defense (DoD) facilities (e.g., Camp Edwards in Massachusetts). Particle dissolution in shallow soil horizons controls the availability of dissolved MC, but the migration of MC through deep vadose zones (120 feet at Camp Edwards) suggests that preferential flow, such as through root traces and macropores, might ultimately be responsible for the observed contamination. Transport of colloidal particles of MC through preferential flow features could also contribute to rapid migration because colloids tend to remain in the fast-flow pathways rather than diffusing into the fine-pore structure of the soil. Rapid transport of MC particles through fractures and macropores could be one of the reasons why aquifer contamination is sometimes observed even in areas where soils are fine-grained and dissolved-phase transport is expected to be slow.
The overall objective of this project is to understand, quantify, and predict the transport of particulate and dissolved MC in realistic vadose-zone conditions. Specific objectives are to determine the potential for preferential transport, which might occur through natural fractures, root traces, and macropores, by using laboratory-scale intact (i.e., undisturbed) soil samples; quantify transport parameters for dissolved- and particle-phase MC under both normal vadose-zone conditions and under storm flow scenarios; and apply these parameters to site-specific subsurface models of operational ranges to predict the potential for mobility of explosive compounds through the vadose zone into underlying aquifers.
Technical Approach
Advanced microscopic techniques will be used to investigate the physical, biological, and chemical relationships between MC particles and preferential flow features in soils. Intact soil samples best represent the chemical and physical structure present in actual operational ranges, and microscopic analysis will determine the importance of colloidal transport of MC in heterogeneous media. Further, intact samples yield reactive transport parameters that are most relevant to the field. Incorporation of both particle- and dissolved-phase MC transport parameters in a reactive transport model will determine the major factors contributing to groundwater contamination at operational ranges.
Benefits
Using a combination of intact soils, microscopic analysis, and flow experiments, this project will investigate all possible contributors to preferential transport of MC in the subsurface: colloids, fracture/macropore flow, and storm flow. Intact soil samples collected from DoD installations will accurately represent processes occurring in soils at these installations. The subsurface of each DoD site will be parameterized with site-specific data. Coupled with the experimental parameters, researchers will determine which scenarios, if any, might lead to contamination of underlying aquifers. (Anticipated Project Completion - 2012)
Points of Contact
Principal Investigator
Dr. Melanie Mayes
Oak Ridge National Laboratory (ORNL)
Phone: 865-574-7336
Fax: 865-576-8646
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
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