## 3 Results and Discussion
### Contents of Pollutants in Roof Runoff
However, the mean fungi quantity was clearly higher than the mean bacteria quantity in all three sampled cities (unlike in the case of roof runoff samples). The observed differences are probably due to a large diversity of factors influencing bioaerosols remaining in the air [29], like temperature, insolation, relative humidity, amount of rainfall, wind, plant cover, traffic, bioaerosol particle size and shape, and some others. The lowest amounts of both bacteria and fungi in the Krakow air were observed in the winter season, which is not consistent with data on microbial composition of roof runoff but stays in line with other studies regarding microbial air quality. The lowest concentrations of bacteria were detected in the Krakow air in winter also by [PERSON] and [PERSON] [79] and by [PERSON] and [PERSON] [80] in the city of Gliwice, Poland. The inconsistency of the results obtained for air and roof runoff is probably caused by the abundance of factors affecting both components. [PERSON] et al. [81; 82] and [PERSON] et al. [83] demonstrated that the (micro)biological condition of roof runoff was mainly affected by weather conditions, like the effects of wind and rainfall. Relatively high amounts of microbiological contaminants detected in Krakow roof runoff with relatively low amounts detected in the air (observed during winter season) may be simply the effect of leaching air bioaerosols by rainfall. Moreover, roof runoff composition was found to be influenced by land use and the characteristics of catchment areas, as well as the technical condition of roofs and the types of roof docking, from which water was harvested [1; 30; 31]. As the roof runoff samples were collected from gutters in Krakow, water had previously washed roof surfaces and collected debris from gutter systems. Therefore, it might contain microorganisms connected with such contaminants, as e.g., feces of birds, mammals, and insects, or putrid leaves [84; 85; 86], not only those contaminants that were typically airborne. The taxonomic identification of strains was beyond the scope of this study; however, it was observed that the majority of the colonies of isolated bacteria were colorful (usually yellow, orange, pink or red). That is typical for airborne microbes, as pigmentation provides better protection against permanent outdoor radiation (especially UV) and prolongs bacterial survival it the air [87]. That observation indicated that the harvested microorganisms originated mostly from the air. Furthermore, [PERSON] et al. [81; 82] noted that airborne microorganisms were significant contributors to the total amount of bacteria detected in the roof-harvested runoff. Moreover bird- and other animal-linked microbiological contamination of roof runoff was considered to be more prevalent in rural rather than urban catchment areas [1]. That observation stays in line with the conclusion stated above, concerning differences between the amounts of microorganisms detected in the air and in the roof runoff in Krakow. It seems then that the main source of microbiological contaminants in the harvested rainwater was bioaerosol washed out from the air, which led to relatively low amounts of microorganisms detected in the air during \"wet\" seasons. Relatively small amounts of fungi (in comparison to those of bacteria) in the Krakow roof runoff (as well as in the case of the Mogilany (MOG) sampling point) may have resulted from the weather conditions. Fungal spores are significant and usually the most abundant contributor to bioaerosol in rural and urban air [88; 89; 90], and although fungi are known to \"like\" humidity, they prefer rather high temperatures and sunny weather. Therefore, spore production may decrease in rainy periods [91; 92] and that could be a reason for their relatively small concentrations in Krakow roof runoff, when compared to bacteria.