In the beginning of 2018 year, front pages of many Eastern European media have been hit by the photos of Martian-like landscapes of mountains, towns and cities covered colored snow. Snow color ranged from yellow to dark red and urged many people to ask the question about the drivers of such phenomenon. United Kingdom’s Met Office and US NASA have synchronously suggested the presence of transported dust particles in Eastern Europe. Such hypothesis was based on spaceborne observations.
More than one year after, the Romanian scientists led by Dr. Luminita Marmureanu from National Institute of Research and Development for Optoelectronics have published the article that reconstructed dust transport even to Eastern Europe and approved initial suggestion about long-range transport of dust to Eastern Europe. On 22-23 March of 2018, Romanian Atmospheric 3D Observatory in Magurele (located on the outskirts of Bucharest) has not only detected anomalous values but received a portion of orange snow that deposited onto the territory of the observatory. Marmureanu and her colleagues explain that on 21 March 2018 a low pressure system was formed over Northern Africa and cyclogenetic processes has lifted numerous dust particles to the atmosphere. Then, the cyclone moved towards Balkans and further to southern Russia.
Prior to the dust event of 22-23 March 2018, the snowfall occurred near Bucharest that consequently triggered deposition of particles (alongside with snow) down to the urban area of Bucharest. Since the observatory is equipped with aerosol particle gravimetric samplers, the scientists were able to analyze morphology of particles in laboratory conditions (see the plot below). It turned out that elemental composition of particles is typical for dust aerosols (i.e. presence of Al, Ca, Mg, Fe and K) despite organic aerosols represent the most typical local aerosol class in Bucharest (> 50% of all observed aerosols during a year).
One of the main arguments supporting the hypothesis about Saharan origin of the dust is that (Ca+Mg)/Fe ratio equals to 1.39 (typical for dust from Algeria, Libya or Egypt). Since the dust was detected during cold time of the year (i.e. heating was on), the scientists have also found the presence of biomass burning particles in the deposited dust. Biological markers (such as presence of diatoms) approved the contamination of dust particles by local biomass burning. On the way to Bucharest, dust particles have traveled 2000 km and one should understand that it is not a limit for aerosols long-range transport. The studies about aerosol particle transportation are important not just because our technology allows detecting and characterizing the path of the particles we cannot directly track. Such studies give an essential clue how dynamic the atmospheric processes are and how aerosols can be transport agents not for mineralogical but also to biological matter (such as viruses or bacteria that can be also easily transported on comparable distances). Content by: MDPI Remote Sensing Open Access Journal
Plots from: Original article of Marmureanu et al., 2019