The sun is in the sky, temperatures rise, the spring is in the air. Finally spring… and not smog. Climate Scientists from the University of Wrocław, throughout the entirety of winter were have been examining the air we breathe and if there were in fact days when the air in Wrocław and other Polish cities was worse than in f.ex New Delhi. Smog wil return to us… during the warmest days.
Applications which track the quality of air could alarm in January and February about a very bad quality of air – the norms were exceeded by 115%, 230% and even 516%.
– These information are not useful because they often refer to the annual norm – explains dr Tymoteusz Sawiński, a climate scientist from the University of Wrocław. As an example: the average annual temperature at the ground level amounts to 15 degrees. Does that mean that when in summer the temperature amounts to 35 degrees, the norm is exceeded by 225%? What does that actually mean? Nothing. Much better is the scale proposed by the Polish Index of Air Quality, which refers, not to the annual norm, but to the momentary values registered here and now. Those are informations that f.ex. the Wrocław magistrate displays at public transport stops. The scale is six-stage and describes well how we should behave in regards to the quality of air – f.ex. to go out or stay at home.
What did the winter season of 2020/21 look like? Climate scientists point out that this time in comparison to previous years the temperatures were lower – average temperature in December, January and February in Wrocław amounted to 0,7 Celsius degrees. For comparison during a significantly warmer season 2019/20 this average in Wrocław amounted to 3,4 Celsius degrees. Actually, there was not a day when the temperature stayed below zero. And the effect of this difference? The average suspended dust concentration PM 2.5 during winter 2019/20 amounted to around 21 µg/m3, and in the current season – 32 µg/m3.
– This mean that air quality was getting worse with every year. Particularly in the morning and in the evening the quality of air could be really bad. Sometimes the suspended dust concentration reached over 100 micrograms per m3. Despite such high concentration, placing Wrocław among the most polluted cities in the world is a gross exaggeration. Among other, we compared data from one of the smog episodes in January. On the day, when Wrocław placed among the three most polluted cities in the world in that IQAir ranking. In fact, we had maximum concentration of suspended dust of 140 micrograms per m3, and at the same time in Asian cities such as Dhaka, Lahore and New Delhi – the concentration amounted to 500 micrograms. The average of this worst period of January for Wrocław was 100 micrograms, and for Asia cities above 200 micrograms – explains dr Sawiński
The same was true in March. From 8th to 10th March, Wrocław,again, placed in the top of the ranking of the most polluted cities in the world, announced on the IQAir website. Do the measurement results justify this inglorious place?
– The maximum concentration of PM2.5 amounted to 97 µg/m3, during this time there was also a seven hour period of poor air quality (according to the Polish Index of Air Quality), and the avergae dust concentration for this period amounted to around 40 µg/m3. Yet such conditions were comparable to other Polish cities, not to mention the abovementioned Asian cities – where average concentration reached 100 µg/m3 and maximum – 200 µg/m3.
Where do these discrepancies come from? Many portals use private dustmeters that are low-cost and logged into an application that automatically transmits data. Such sensors perform a very important function – they transmit information about air quality from locations, where there are no professional, constantly supervised measuring stations, f. ex. from the GIOS network. At the same time, data from such low-cost sensors should be treated with caution – their accuracy and reliability is much poorer than that of professional sensors. They can be a good lead, but at the same time they can also mislead us and cause unnecessary panic.
A temperature of a dozen degrees means that air quality will improve. However, as the climate scientist from the University of Wrocław reminds us, when the heat comes along, smog will return to us, but this time related the exhaust fumes from the cars.
– Tropospheric ozone is formed by converting nitrogen oxides from the combustion of liquid fuels. When it is warm, and especially hot, there is a photochemical reaction. Nitrogen oxides transform into ozone, and this one is poisonous. In the lower atmosphere, ozone pollution is the so-called smog – says dr Sawiński.
The Institute of Geography and Regional Development of the University of Wrocław has been conducting air research in Wrocław for many years. Measurements are being carried out 24hours a day, all days of the year and made available on the website of the Department of Climate Science and Atmosphere Protection. Currently, the Institute is also working on a big project devoted to air quality – “Do you know what you breathe?” – an educational campaign in aid of cleaner air.