Compound Specific Isotope Analysis of Mineral-Mediated Abiotic Reduction of Nitro Compounds
Abstract
Methods are needed to verify that abiotic attenuation of energetic compounds, such as trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), in groundwater is occurring, and it must also be possible to verify that strategies to enhance abiotic processes are having the desired effects. The overall objective of the project is to quantify the isotope fractionation factors of nitro compounds, including new components in insensitive munitions, during their abiotic reactions with iron bearing minerals. The central hypothesis is that abiotic attenuation processes will lead to specific fractionation of carbon (C) and nitrogen (N) contained with the pollutants. Specific objectives were to measure isotope enrichment factors during the abiotic reduction of nitroaromatic and nitramine explosives and assess how solution conditions and multiple reduction cycles influenced these values. Testing of the overall objective was met by accomplishing the following overall tasks 1) Mineral Synthesis and Characterization, 2) Kinetic Studies with Synthetic Minerals, 3) Compound Specific Isotope Analysis (CSIA) method development, 4) Kinetic Studies with Natural Materials, and 5) Testing of Regeneration/Enhancement of Reactivity. CSIA was performed on samples collected from batch and column reactors in tasks 2, 4, and 5. Reaction conditions (mineral identity, pH, presence of natural organic matter) influence reaction kinetics, but the isotope fractionation of N and C is unaffected by reaction conditions. Additionally, the fractionation measured with natural materials is similar to that with synthetic materials, and regeneration of reactivity with dithionite also leads to consistent isotope fractionation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 21, 2021
- Accession Number
- AD1154363
Entities
People
- Bridget A. Ulrich
- Jennifer H. Strehlau
- Matthew J Berens
- Thomas B Hofstetter
- William A. Arnold
- Yiran Tong
Organizations
- University of Minnesota