This paper presents a 120-day-long variability of chemical composition of submicron particulate matter (PM1) over Warsaw. The content of the following components was examined in the PM1 mass: primary (POM) and secondary (SOM) organic matter, secondary inorganic matter (SIM), elemental carbon (EC) as well as Na and Cl ions (primary inorganic matter). The 24-hour concentrations of PM1 were subject to seasonal fluctuations which are typical of urban areas in Poland; their values averaged 11 µg m–3 in summer and 17 µg m–3 in winter. Most of the PM1 components and gaseous pollutants (SO2, NO2 and NOx) revealed higher mean concentrations in winter than in summer. A statistical analysis of meteorological parameters and 24-h concentrations of PM1, PM10, SO2, NO2 and NOx confirmed a significant influence of air temperature and precipitation on the concentration patterns of these pollutants over Warsaw. The highest concentrations of PM1 occurred in winter for the following wind directions: S, SE, N and NE; in summer for NE, E and S. The analysis of back trajectories demonstrated that on days with the highest 24-h concentration of PM1 polluted air masses arrived from S and SE and affected the concentration of PM1 over Warsaw. The submicron particulate matter, in as much as 62%, comprises secondary matter (SOM and SIM). The primary sources of its precursors and – to a smaller extent – of the primary matter as well – are traffic and combustion of various fuels for the purpose of heat and power generation. Their average contribution to the development of PM1 was 15% and 51%, respectively, for the entire period of observations.

The aim of the study is the assessment and analysis of the variability of human-bioclimatic conditions in southern part of Warsaw, depending on the atmospheric circulation in the long-term (1998–2015). The Universal Thermal Climate Index UTCI was applied to evaluate the human-bioclimatic conditions using meteorological data for the 12:00 UTC obtained from the WULS Ursynów weather station. In order to determine the relationship between the UTCI and its corresponding synoptic situation, the circulation type classification proposed by Lityński was used. It was found that the period from the second decade of April to the first decade of October is the most favourable one for recreation and relaxation. The situations not caused by thermal loads of humans are the most frequent and the values vary from 42.9% in October to 66.6% in August. Whereas weather conditions causing the ‘strong’ and ‘very strong heat stresses’ and the ‘strong’ and ‘very strong cold stresses’ were relatively rare. The analysis of influence of atmospheric circulation on bioclimatic conditions has shown that the most favourable conditions with no heat load (class 0) of the body occurred during cyclonic circulation in the summer (70%) mainly at advection from the North and South. Particular analysis of selected most strenuous days of the heat wave and the cold wave confirmed the occurrence of a high frequency of conditions stressing the human body with ‘strong’ and ‘very strong heat’ as well as ‘strong cold’ for most of the day during anticyclonic circulation in both cases.

The research area includes one of the largest in terms of population and also the most attractive tourist area in Poland—Warsaw agglomeration. The aim of the study is to assess the temporal and spatial difference of the heat stress on the human body in this area based on long-term data (1980–2016). On the basis of the Universal Thermal Climate Index (UTCI) and designated Climate-Tourism-Information-Scheme (CTIS) diagrams, a comprehensive and detailed bioclimate assessment was made for three different areas. The highest values of the UTCI as well as the frequency of thermal sensations related to heat stress occurred at the Bielany station representing the city area, and the lowest at stations representing suburban area—Legionowo and outskirts—Okęcie. A negative linear trend of the number of days was observed for thermal stress related to cold stress and the category of ‘no thermal stress’ while a positive linear trend was obtained for thermal stress related to heat stress. Based on the obtained results, it can be concluded that in summer months (in June over 60%) the conditions are favourable for the residents causing the lack or slight intensification of the body’s adaptation processes and they are beneficial for practicing various forms of recreation and tourism. However, on the other hand, the rise in the number of days with the ‘strong and very strong heat stress’ especially at the station representing the city area is a disturbing factor and negatively affecting both the health and well-being of agglomeration residents in the future.

Green areas situated inside the city play a very important role for many aspects. Among other, from the social point of view, they have a positive impact on the life of city habitants: directly improve well-being and health, reduce noise, provide opportunities for activity and recreation, improve the tourist attractiveness of the city, etc. The objective of this study was to assess thermal sensations and preferences of people staying outdoors for recreational purposes in the area of the city park during summer 2019, as well as to identify how bioclimate perceptions are modified by personal factors (physical and physiological). In order to determine the optimum thermal zone for recreation and urban tourism during the summer, the regression model for mean thermal preferences (MTPV) every 1 °C in PET value intervals was calculated, and according to this procedure, the preferable spectrum of thermal conditions for tourism and recreation in Warsaw which is related to the PET value range between 27.3 and 31.7 °C. All age groups indicated the highest frequency of neutral thermal sensation vote, which decreased with feeling more extreme thermal conditions. In the case of classification by the gender, the men more than the women indicated the thermal conditions as neutral, “slightly warm,” and “warm.” Studies have shown that women were more sensitive than men to extreme thermal sensations especially “hot” and men more often than women indicated greater acceptance for comfortable and warmer thermal conditions.

The aim of our study was to examine the literature on the phenomenon of the so-called “Weekend Effect” (WE) in Warsaw and its outskirts. An analysis of the temporal and spatial distribution of ozone and nitrogen dioxide concentrations was made using hourly data on ozone and nitrogen dioxide concentrations in the period from May to September 2008 to 2012 from automatic air quality monitoring stations in Warsaw. The analysis uses data for seven stations located in different parts of the conurbation, which represent different types of areas. WE was then calculated using four methods, one of which was based on a calculation of the difference between the maximum daily ozone concentrations on weekends and the concentrations on weekdays. The results showed that most stations see higher concentrations of ozone during the weekend than on weekdays. This confirms the existence of WE, especially in the area of Granica, west of Warsaw in Kampinos National Park. At stations located within the city, average and maximum values of daily ozone concentrations are 13% and 8% higher on weekends than on weekdays, respectively, despite a reduction in NO₂ concentrations of about 20%. Analysis of the diurnal ozone and nitrogen oxide (NO_x) behaviour confirms the hypothesis that the most likely cause of the higher mean ozone levels on weekends is a reduction in ozone suppression due to lower NO_x emissions on weekend mornings. The reduction in emissions in industrial/traffic-heavy sectors on Sunday leads to a greater reduction in NO_x relative to volatile organic compounds (VOC), and thus an increase in VOC/NO_x ratios during weekends.