Assessing the Abundance of Pyrotechnic Traces from New Year′s Eve Celebrations in the Netherlands: Implications for Forensic Explosives Investigations

To ensure a correct interpretation of the presence and abundance of pyrotechnic traces at a crime scene, it is essential to understand reference background levels and the extent to which they are affected by specific activities such as fireworks displays. A total of 112 objects throughout the Netherlands were sampled before and/or after New Year ' s Eve 2017, 2018, 2022, and 2023. Sample extracts were analysed with Ion Chromatography - Mass Spectrometry to determine the concentrations of 17 inorganic ions relevant to forensic explosives investigations. The ions SO42-, NO3-, Na+, K+, Cl-, PO43- Ca2+, Mg2+, and NH4+ were found most often (33-98%) before New Year ' s Eve. The maximum amounts recovered ranged from 52.63 to 1071.50 mu g for this set of ions. Only 3% of outdoor objects carried detectable levels of ClO4-, with a maximum amount of 0.55 mu g per 2.3 dm2. It appears that NO2-, SCN-, ClO3-, S2O32-, Li+, Sr2+, and Ba2+ are generally absent in the Dutch environment. While fireworks displays do not seem to greatly affect the background levels of inorganic ions related to explosives, mean ClO4- levels were increased on January 1st (p=0.02). Sporadically, high levels of Cl-, SO42-, K+, and even a trace amount of Sr2+ were observed after New Year ' s Eve. These findings are of great forensic relevance for pre- and post-explosion investigations involving trace levels.