Validation of Stable Isotope Ratio Analysis to Document the Biodegradation and Natural Attenuation of RDX

Dr. Paul Hatzinger | APTIM Federal Services

ER-201208

Objectives of the Demonstration

The objective of this project is to validate a compound-specific isotope analysis (CSIA) method to quantify aerobic and anaerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) at field sites. This technique will provide critical information concerning the potential for natural attenuation of RDX at former and current Department of Defense (DoD) installations.

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Technology Description

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Collection of RDX for Stable Isotope Analysis

CSIA is increasingly being applied as an analytical tool to quantify the biodegradation and environmental fate of industrial and military pollutants, including chlorinated solvents, gasoline oxygenates, perchlorate, and explosives. This technique relies on the fact that bacteria biodegrade heavier isotopomers (e.g., RDX with 15N rather than 14N in its structure) more slowly than lighter ones due to the greater bond stability of the heavier molecules, leading to enrichment in the heavier isotopes within the residual parent molecules as biodegradation proceeds. An analysis of stable isotope ratios of a contaminant along the flow path of a plume or in contaminated groundwater compared to the contaminant source material can be used to document degradation and natural attenuation in situ, as well as provide information on specific reaction mechanisms, particularly if isotopes of multiple elements are evaluated. Thus, CSIA is a powerful and versatile technique in environmental assessment.

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Implementation Issues

This project will provide DoD with a validated CSIA approach for quantifying RDX biodegradation at ranges and other field locations with large dilute plumes where in situ or ex situ remedial options are costly or impractical. Because RDX degrades to several terminal products that are common in nature (e.g., HCHO, N2O, NO3-, NO2-, CO2), this methodology may be critical to determining the potential success of monitored natural attenuation (MNA) as a selected remedial option at such locations. At the conclusion of this method validation project, a DoD Guidance Document will be developed to describe the stable isotope approach for RDX in detail and discuss the appropriate application and interpretation of results for MNA applications. (Anticipated Project Completion - 2018)

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Publications

Fuller, M.E., L. Heraty, C.W. Condee, S. Vainberg, N.C. Sturchio, J.K. Bohlke, and P.B. Hatzinger. 2016. Relating Carbon and Nitrogen Isotope Effects to Reaction Mechanisms During Aerobic and Anaerobic Degradation of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Pure Bacterial cultures. Applied and Environmental Microbiology, 82(11):3297-3309.

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Points of Contact

Principal Investigator

Dr. Paul Hatzinger

APTIM Federal Services

Program Manager

Environmental Restoration

SERDP and ESTCP

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