Recreating Explosion Conditions from Remnant Soot Aerosol

JAMES E. LEE, Allison Aiken, Rachel Huber, Madeline Stricklin, Ryan Farley, Los Alamos National Laboratory

     Abstract Number: 414
     Working Group: Chemicals of Emerging Concern in Aerosol: Sources, Transformations, and Impacts

Abstract
Soot generated by the detonation of explosive materials bear the signatures of the environment that they were formed in. Those environments are dictated by the explosive material, device construction, and oxygen availability. Conversely, analyzing particle composition and structure can provide forensic information about the explosive device. Here, we investigate soot from contained explosive experiments using a laser-vaporization high-resolution time-of-flight mass spectrometer (Aerodyne Research Inc. Soot-Particle Aerosol Mass Spectrometer, SP-AMS), a novel approach for post-detonation soot forensics. In contrast to standard solvation-based laboratory analysis, the SP-AMS is designed to directly measure particles providing the possibility of real-time results and analysis of single particles. Soot samples were collected from three detonation experiments using the same explosive materials and detonation configurations but changing the atmospheric conditions (either ambient atmosphere or oxygen-limited). We identify discriminating characteristics which include the abundance of black carbon, presence of fullerenes, incorporation of metals in black carbon bearing particles, and elemental ratios of organic-like material. These signatures were consistent in replicate explosive experiments and can be explained by known chemical reactions and particle formation dynamics following detonation. Forensic analysis with this approach can be performed on soot samples collected on air filters or scrapped from nearby surfaces. Chemical signatures were observed in bulk particle analysis where their characteristics are muted by the averaging of compositionally-varying particles. Our results provide a road map for future analysis investigating other high explosive materials and device constructions, analysis of single-particles where the signatures may be more distinct, and statistical classification strategies.