δ¹³C and δ¹⁵N Values of Residues Provide Insights Into Identification of the Explosive Source

Postblast analyses of military and terrorist events will benefit from the capacity to learn more about the explosive materials used in an event. Here stable isotope ratio analyses (δ¹³C, δ¹⁵N) can provide additional information to complement identification of the explosive components.

Controlled detonations using different types of military-grade explosives were conducted in 55-gal barrels. Additionally, soil analyses were conducted following Mark-84 field detonations. Swab materials and soils were purified to analyze explosive compounds using established HPLC and IRMS techniques.

Explosive materials were recovered in the residues of TNT (aromatic-based explosive) and RDX (nonaromatic explosive) detonations in barrel experiments. Explosive residues were not recovered from PETN (nonaromatic explosive). Postblast δ¹³C and δ¹⁵N values of TNT residues were similar to δ values in the source explosive, suggesting minimal enrichment in δ residues. While δ¹⁵N values of RDX in postblast residues were also similar to preblast source values, postblast RDX δ¹³C values were enriched by almost 2‰ relative to the preblast explosive. Similar patterns were observed in HMX, RDX, and NT recovered from soils following Mark-84 detonations.

δ¹³C and δ¹⁵N values can be effectively measured on explosive compounds recovered in residues following detonations. Residue δ¹³C and δ¹⁵N values can be linked to δ values of undetonated explosive compounds. Additional field studies should be conducted to verify these results.