Air pollution before and during the pandemic. A comprehensive study of AGH UST employees

The level of environmental pollution around the world remains awfully high. This includes Poland, which also struggles with the problem, especially in the field of air pollution. The harmful air that the Poles breathe causes, for example, inflammations and allergies, as well as many other civilisation diseases related primarily to the respiratory or cardiovascular systems. A particularly dangerous fraction is PM2.5, which contains particles that do not exceed 2.5 µm in aerodynamic diameter. They can easily filter in our lungs and blood, causing serious afflictions. Another important thing, in addition to concentration, is the chemical composition of the pollutant, which determines its properties.

‘Particulate matter (PM) is made up, in about 40%, of the carbon fraction, which, in turn, is composed of organic carbon (OC) and elemental carbon (EC). As a result, we receive the so-called Equivalent Black Carbon (e-BC), which is produced during incomplete fuel combustion. PM also contains socondary inorganic aerosols, for example, sulphates or ammonium nitrogen, that amount to 20–30%. Yet another ingredients are elements (4–10%), remaining ions, and mineral matter’, says Prof. Lucyna Samek, presenting the composition of the PM.

Research problem

In response to excessive levels of pollution, norms have been introduced that determine the acceptable concentration of harmful substances. Such recommendations were proposed, for instance, by the World Health Organization (WHO) and the European Environment Agency (EEA), which has established the acceptable average annual concentration level of the PM2.5 fraction at 20 µg/m3, starting from 2020. To comply with these norms, countries and cities take action to reduce pollution emissions. In Krakow, which is particularly affected by the problem of particulate pollution, in September 2019, the authorities introduced a ban on burning coal and wood.

The aforementioned law may be a significant factor influencing the change in air pollution characteristics in the city area in the past two years. Another such factor might be the COVID-19 pandemic and all the lockdowns related thereto, which were introduced shortly after the ban. Having collected a considerable amount of samples during the academic years 2018/2019 and 2020/2021, the AGH UST scientists began meticulously analysing changes in the concentration and composition of air pollution in the city, which could have occurred between the two periods as a result of both factors.

Exhaustive analysis

As part of the project, university employees have conducted extensive studies. The researchers have indicated the composition and concentration of particular elements of the PM, but also its emission sources. The entire investigation process began on the roof of the D-10 building, where a station is located from which the scientists collected the pollution samples. To determine the concentration of PM in micrograms per cubic metre, its mass, which had been measured by weighing the filters before and after sample collection, was divided by the air volume that flew through the probe in 24 hours. Subsequently, the filters were transferred to a laboratory, where they were thoroughly tested.

Further analyses were to establish the precise composition of the PM and the concentrations of particular substances. The first step was to use the energy-dispersive X-ray fluorescence method, which allowed the scientists to determine the concentrations of 21 elements. The next stage consisted of determining the e-BC concentration, that is, the elemental carbon that absorbs the spectrum of light from ultraviolet to infrared. To achieve this, a modern spectrometer was used, which was acquired by the research team as a result of funding from the International Atomic Energy Agency (IAEA). At the Faculty of Energy and Fuels, using the ion chromatograph, the scientists determined the concentrations of water-soluble ions.

On the basis of the results, it could be concluded that the concentration of individual elements between the two periods has slightly decreased. Furthermore, the e-BC concentration exhibited seasonal variability with concentrations two times higher in the winter months than in the summer months. Nevertheless, the interdisciplinary analyses of the scientists from the AGH UST Faculty of Physics and Applied Computer Science did not end there. The data acquired in the laboratory were entered into a single spreadsheet, which was then put into a statistical program using the positive matrix factorization method (PMF). This allowed the scientists to identify the type of emission sources and their share in the overall PM mass.

‘The data from ion chromatography, X-ray fluorescence, and light transmission were merged into one Excel file. In each of such spreadsheets, we put in the concentration values of particular PM ingredients and the uncertainty of these concentrations. Then, we entered the information into the statistical program that uses the PMF method, which allowed us to identify the sources’, explains Prof. Lucyna Samek.

Practical dimension

Thanks to the statistical program, the AGH UST scientists were able to model and identify the sources of air pollution, as well as to determine the way in which their overall share has changed in the academic year 2018/2019 as opposed to the year 2020/2021. The data related to the changes in air pollution that the research team obtained make it possible to adjust the emission limits to current conditions. They can also serve as a basis for city or provincial offices and authorities in their plans to reduce the levels of harmful substances in the atmosphere.

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The project is funded by a university grant within the framework of the project ‘Initiative for Excellence – Research University’ (AGH UST 2021–2023).