On September 18, 2024, at approximately 01:00 UTC (04:00 local time in Romania), a large-scale explosion occurred at an ammunition depot near the town of Toropets, in the Tver region of Russia, approximately 500 kilometers from the Ukrainian border.
According to reports from Ukrainian, Russian, and international media sources, the explosion was caused by a coordinated drone attack attributed to Ukrainian forces. Estimates indicate that the Toropets depot housed approximately 30,000 tons of military ordnance, including missiles intended for Iskander missile systems, Tochka-U missile systems, guided aerial bombs, artillery ammunition, as well as fuel storage tanks. Several hangars were struck during the attack, resulting in massive secondary explosions.
The event was also detected by seismo-acoustic monitoring stations located in Romania, confirming the magnitude of the incident.
The dispersion of particles released by the explosion was analyzed and simulated using the HYSPLIT model. Given the estimated detonation of 30,000-ton munitions, the release of fine particulate matter (PM₂.₅) was expected, reflecting the high-temperature combustion and shockwave-driven fragmentation typical of explosive events. The model was configured with a dominant particle size fraction of ~2.5 µm, and meteorological data from GDAS were integrated to track regional transport. Initial results indicated hazardous PM₂.₅ concentrations near the source and persistent plumes extending over 200 km downwind.