Short duration urban dust events driven by wind induced resuspension: observational evidence from a European city and inverse CFD analysis

Short duration but high intensity particulate matter (PM) bursts are typically associated with arid environments, however, due to climate change and prolonged dry periods, these events could happen in European cities too, where they remain poorly documented. Here a drivers and impacts of an intense PM event which occurred in Bratislava (Slovakia) are investigated, following a prolonged dry period and a fast moving cold front with combination of meteorological observations, spatially differentiated PM monitoring data, historical event screening and inverse dynamic CFD simulations. The event coincided with an abrupt stabilization of wind direction and increasing wind speed, while precipitation arrived several hours later. Peak PM concentrations occurred before the maximum wind speed, indicating a threshold controlled phenomenon. Given the upwind land cover towards the city centre dominated by urban and forested areas and the lacking major agricultural sources, the episode in the city centre is most consistently explained by wind driven resuspension of urban surface dust. While wind induced resuspension itself is well known, the temporal structure of short urban dust bursts and their representation in standard air quality data remain poorly constrained. To quantify the short time scales involved, a unique dynamic inverse model was applied using idealised CFD simulations of resuspension, which shows that particle concentrations can rise sharply within 6 to 8 s after resuspension happen, producing a short lived but intense concentration peak, followed by a longer lasting low intensity tail sustained by transport across the city. Model results suggest that mean concentrations during the first minute must reach several hundred μ g.m 3 , with instantaneous peak concentrations plausibly exceeding 10 2 to 10 3 μ g.m 3 . A retrospective analysis of long term air quality data (2009 to 2024) identified several similar short lived events, indicating that such urban dust resuspension episodes recur episodically and cold probably happen in other cities too, but are likely substantially underestimated by routine air quality indicators based on hourly averaging.