Matrix-dependent dissolution of CO₂-laser-generated surrogate nuclear explosion debris

Rapid and accurate elemental characterization of nuclear explosion debris by inductively coupled plasma mass spectrometry (ICP-MS) requires complete sample dissolution. Existing dissolution methods have been developed primarily for silica-rich historic debris and environmental analogs which may not represent debris generated in urban or infrastructure-rich environments. In these settings, substantially greater concentrations of Fe- and Al-bearing materials capable of altering the dissolution behavior through the formation of refractory fluoride phases are expected. To evaluate these effects, three fluorination-based digestion methods, HNO₃-HF, HNO₃-HF-HCl, and ammonium bifluoride (ABF) fusion, were compared using a certified Montana soil (SRM 2710a), a synthetic Fe/Al-rich oxisol, with corresponding CO₂ laser-generated surrogate nuclear explosion debris (SNED) and historic trinitite. Elemental recoveries, analytical precision, and apparent enrichment/depletion following laser-induced melt formation were evaluated by ICP-MS. All three digestion methods generally produced comparable recoveries for the precursor soils, indicating that digestion chemistry exerted only a modest influence for each individual precursor prior to melt formation. In contrast, substantially greater differences emerged for laser-generated SNED, which produced heterogeneous beads with increased matrix-dependent analytical variability, particularly in the Fe/Al-rich oxisol system. For example, ABF reduced the relative standard deviation for Al from 31% with HNO₃-HF to 5.7% and for Sr from 37% to 3.5%, demonstrating that the choice of digestion method can substantially affect the analytical variability following laser-induced melt formation. The apparent enrichment or depletion results indicate that dissolution performance is governed not only by digestion chemistry but also by the composition and thermal history of the sample. Historic trinitite generally exhibited reproducible elemental measurements across the three digestion approaches, although direct quantitative comparison of dissolution efficiency was not performed. Overall, the results demonstrate that dissolution behavior depends on both matrix composition and the chemical or physical changes produced during rapid laser melting. These findings support the use of compositionally representative SNED materials for evaluating and optimizing analytical workflows for complex nuclear debris.