Concentration and Size Distribution of Culturable Bacteria in Ambient Air during Spring and Winter in Gliwice: A Typical Urban Area

The concentrations and size distributions of culturable bacterial aerosols were measured during spring and winter in outdoor air in Gliwice, Upper Silesia, Poland. This research on culturable bacteria was carried over a period of two years. The samples were collected using a six-stage Andersen cascade impactor (with aerodynamic cut-off diameters of 7.0, 4.7, 3.3, 2.1, 1.1, and 0.65 μm). The results showed that the average concentration of culturable bacterial aerosol was 355 CFU m−3 in spring, which was four times higher than during winter (65 CFU m−3). Bacterial aerosol concentrations showed the unimodal size distribution with the highest range of 3.3–4.7 μm particles. The seasonal distributions of bacterial aerosol grain clearly indicate that, in winter, the size distribution of particles <7 μm is more “flattened” and is characterized by an increased share of fine fractions and a decreased share of coarse ones. Environmental parameters, such as temperature, UV radiation, relative humidity, wind velocity, as well as PM10 and PM2.5 concentrations, were measured in order to analyse whether environmental factors had any effect on bacterial aerosols. Statistically, the most important meteorological factors in the viability of airborne bacteria were temperature and UV radiation