Locations of traffic accidents and fallen trees on roads related to the glaze occurrence (1–3 December 2014).

The paper analyzes suspended particles number concentrations of 61 size fractions (184 nm to 17,165 nm) in the air at a traffic location. The average course of the individual fractions was analyzed at various intervals – daily, weekly, monthly and annually, in the period between 2017 and 2019. The data was then used to calculate the arithmetic mean for all the fractions (MS Excel, R) and then using a proprietary web application, heatmaps were constructed. The obtained results showed significant differences in both the annual and daily variation of number concentrations between the individual fractions differing in particle size. In the case of the annual variation, one can see a greater variability of smaller particles, which is most likely due to the source of the actual suspended particles. Meteorological and dispersion conditions are found as important factors for suspended particle concentrations. These can lead to significant differences from year to year. However, a comparison between 2018 and 2019 showed that even though the average absolute number concentrations can differ between years, the actual relative number concentrations, i.e., the ratios between the individual fractions remain very similar. In conclusion it can be said that the difference between the number concentration variation of the size fractions depends on both the actual pollution sources (especially in the long-term, i.e., the annual variation) and the actual size of the particles, which plays a role especially in the short-term (daily, weekly variation).

The main focus of this study is the effect of drought on air quality in the Czech Republic. PM X (PM10 and PM2.5) concentrations at 21 air quality monitoring stations of different types (rural, suburban and urban) were studied during a 10-year period from 2010 to 2019. Only data measured during the vegetation period (Apr-Sep) were used. In addition, other meteorological factors were taken into account as well, in particular wind speed, air and soil temperature and soil moisture. It was found that PM10 concentrations were higher by 26.7 to 46.7% during dry periods with the difference being statistically significant. A strong correlation was found between PM10 and PM2.5 concentrations and the soil temperature and moisture, particularly at the top soil layer (0-10 cm depth). Results of the study show that soil moisture affects the extent of resuspension and soil erosion. Soil moisture values above 36% create unfavourable conditions for resuspension or erosion even when soil temperature is higher than 20 °C.

Evaporation from water surface at the station in Ústí nad Orlicí was measured using an automatic EWM evaporimeter. The analysed period was from May 1st to September 30th in the years 2001 to 2014. Statistical analysis of the daily evaporation showed that the values ranged between 0.0 mm and 7.3 mm (July 17, 2007). This maximum value was analysed in detail and considered to be realistic based on the unusual weather conditions on that day. The highest average daily evaporation was observed in July (2.8 mm), followed by August (2.5 mm). On the other hand the lowest average daily evaporation was found to be in September (1.6 mm). Average monthly evaporation totals in the analysed period (2001–2014) ranged from 49.1 mm (September) to 86.1 mm (July). The absolute lowest monthly evaporation total in the analysed period was measured in September 2002 (34.4 mm), on the other end of the scale, the absolute highest monthly evaporation in the period of interest was measured in August 2003 (114.5 mm). Statistics of annual data show that out of the 14 years analysed, the lowest evaporation was observed in 2005 (263.5 mm), while the highest in 2007 (426.1 mm). Average annual (May-September) evaporation for the 14 years is 355.0 mm. The trend in evaporation for May and August is negative, in the other months it is positive. The largest change was seen in July, where the linear index value is +1.555. However, the trends in monthly values are not statistically significant.

No abstract