Exploring the Utility of Compound-Specific Isotope Analysis for Assessing Ferrous Iron-Mediated Reduction of RDX in the Subsurface

Subsurface contamination with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) at ordnance production and testing sites is a problem because of persistence, mobility, toxicity RDX formation toxic products under anoxic conditions. While utility compound-specific isotope analysis for inferring natural attenuation pathways from stable ratios has been demonstrated, fractionation reduction by iron-bearing minerals remains unknown. Here, we evaluated N C during Fe(II) associated Fe sediments applied to assessment mineral-catalyzed in contaminant plume sediment columns treated situ chemical reduction. Laboratory studies revealed that was reduced nitroso compounds without denitration concomitant ring cleavage. Fe(II)/iron oxide reactions exhibited enrichment factors, ?N, between ?6.3±0.3‰ ?8.2±0.2‰, corresponding an apparent 15N kinetic effect 1.04–1.05. The observed variations ?15N ?15‰ groundwater samples suggested extent reductive transformation 85% ammunition plant. Conversely, masking after laboratory flow-through systems, which presumably due limited accessibility reactive Fe(II).