Intense desert dust event in the northern Adriatic (March 2020); insights from the numerical model application and chemical characterization results

The untypically extreme and sudden particulate matter outbreak set stage over Balkan region from 27 to 30 March 2020. The available observations at air quality stations in Croatia recorded the hourly PM10 concentrations up to 412 μgm-3. Meteorological analysis shows the PM10 concentrations increase was primarily affected by advection of mineral dust from the desert area east to the Caspian Sea. The anticyclone north of Croatia and cyclone over Anatolia formed a strong pressure gradient driving a transport from the east. The backward trajectories as well as satellite products indicated the dry Aral Sea as a major source of dust. A dust plume affected the PM10 increase observed in Croatia, starting at Osijek and easternmost air quality stations . Modeling study shows the vertical extension of a plume was up to ~2 km. However, the PM10 chemical (Pb, Cd, Cu, Zn, Fe, Mn, PAHs) and morphological (SEM analyses) composition at the site in the northeastern Adriatic revealed mainly the presence of the Saharan dust. Preceding the Asian dust advection, the Saharan dust transport towards Balkan driven by Sharav cyclone was observed in PM10 at several stations in the Adriatic and continental Croatia on 26 March 2020. Modeling results showed the Saharan dust transport was at levels below ~ 8 km. The mixing of the Asian and Saharan dust plumes over Balkan was favored by subsidence due to anticyclonic high pressure conditions, and it is the most likely explanation for the observed PMs chemical and morphological results.