Eight aerosol samples were collected in Krakow using a low-volume sampler in February and March 2019 during variable meteorological conditions and times of the day, to study their single particles’ properties (size, morphology and chemical composition analyzed using a scanning electron microscope fitted with an energy-dispersive spectrometer) and microbiological characteristics. The content of particles of different chemical compositions larger than 2.5 μm was low. Considering the number of the particles, submicron particles strongly dominated with a high content of ultrafine particles (nanoparticles). Tar ball-type particles were relatively common in the studied samples, while soot was the dominant component. Soot was present as small agglomerates composed of few particles, but also as bigger agglomerates. Metal-containing particles of various chemical characteristics were abundant, with transition metals commonly occurring in these particles. The physicochemical characteristics of aerosols indicate that despite a relatively low mass concentration, their adverse health impact could be very strong because of the high content of nanoparticles, the abundance of soot and other fuel combustion-related particles, and the high incidence of transition metal-rich particles. Microbiological analysis was based on cultures on both solid and liquid agar. The MALDI-TOF method was used for species identification—for bacteria and fungi. Twelve different species of bacteria were isolated from the collected samples of aerosols. The most frequently isolated species was Gram-positive sporulating Bacillus licheniformis. The isolated mold fungi were of the genus Aspergillus.

For several decades air pollution in Krakow has been a serious and an unresolved environmental and social problem. The causes of high concentration of particulate matter, such as PM10 and PM2.5 in Krakow are both natural and anthropogenic. Nevertheless, the sources of dust pollution have not been fully determined yet. The main source of dust in Krakow is local emissions, however, particles from adjacent areas might also contribute significantly to the pollution. Transboundary dust should also be taken into account while investigating the problem. The aim of the study is to determine what type of particles are present in the atmospheric air in Krakow and to make an attempt at determining their sources. The analytical method applied in the study was the Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS). In addition, the HYSPLIT model was used for data analysis and for determination of particles source areas. The analysis of individual dust particles indicates that they are very diverse in terms of chemical composition and particle size. Moreover, the analysis shows that the particles are of various origins, such as anthropogenic and natural, as well as that some of them are formed in the air by chemical reactions. The analysis of particulate matter demonstrates that the majority of it consists of particles with a diameter of less than 1 μm. The concentration of very fine soot particles (nanoparticles) seems to be the highest, however, spherical aluminosilicate particles such as iron and titanium oxides are also found.

This article presents research into the meteorological conditions underpinning the development of night thunderstorms in Poland. The main objective was thus to identify the synoptic situations favouring nocturnal thunderstorms, as well as to determine which convection indices are of greatest relevance to forecasts of this type of thunderstorm. The research detailed here was carried out by analysing cloud-to-ground lightning flashes registered in Poland in the years 2002‑2018 via the PERUN system. ERA 5 reanalysis was used to obtain relevant atmospheric parameters and convection indices. In addition, synoptic analysis was carried out for specified thunderstorms, with their dominant structure also determined. No fewer than 1.5 million cloud-to-ground lightning flashes were analysed for the purposes of this study. These data making it clear that the development of nocturnal thunderstorms is favoured primarily in conditions of a waving front, cold front or wind convergence line. In all cases, the jet stream in the upper troposphere emerged as an additional factor increasing the development and activity of nocturnal thunderstorms.