# A Regional Multi-Agent Air Monitoring Platform
## 3 State of the Air in Plovdiv
The image (Figure 4) is a chart comparing annual levels of fine particulate matter (PM2.5 and PM10) in Plovdiv-TRACIA, Bulgaria, for different sources and years. The chart is interesting and relevant because it shows how air pollution levels have changed over the years and how they compare to current EU air quality standards. This is important for assessing air quality and taking measures to improve the environment. The annual data from our and external sources for the Plovdiv-Trakia region for PM2.5 and PM10 by year compared with data from the European Environment Agency and EU standards show the following:  
* In 2022, the levels of PM2.5 (18 \(\upmu\)g/m\({}^{3}\)) and PM10 (24 \(\upmu\)g/m\({}^{3}\)) were above the EU standard, and they increased in 2023 to PM2.5 (21 \(\upmu\)g/m\({}^{3}\)), PM10 (29 \(\upmu\)g/m\({}^{3}\)), leaving the values above the limit. * Data from the European Environment Agency in 2022 show PM2.5 levels of 17 \(\upmu\)g/m\({}^{3}\) and in 2023, the levels are 16 \(\upmu\)g/m\({}^{3}\). These levels remain stable but still above the EU standard. Data in 2022 for PM10 (33 \(\upmu\)g/m\({}^{3}\)) levels are also above the EU standard and increased to 37 \(\upmu\)g/m\({}^{3}\) in 2023. In the period from 2022 to 2023, the levels of PM2.5 and PM10 in Plovdiv-Trakia remain above the EU standards, and an increase is observed, especially for PM2.5. When compared with data from the European Environment Agency for the same period, PM2.5 levels remain relatively stable. PM10 levels are high, exceeding the EU standard more than twice in 2023. The data show that the air quality in Plovdiv-Trakia is not within the permissible limits according to both EU and European Environment Agency standards. The chart (Figure 5) shows the annual levels of fine particulate matter (PM2.5 and PM10) for the Sahat Tepe area of Plovdiv and it also compares the current European Union (EU) standards and European Environment Agency data for 2022 and 2023. Our measurement data in 2022 and 2023 show that the levels of PM2.5 and PM10 in the Sahat  
Figure 4: A chart showing the concentration of fine particulate matter for Plovdiv-Thrace/Trakia. For a better understanding of the pollution in the city of Plovdiv, we consider our other sources located in different areas of the city (Plovdiv-Western District; Plovdiv-Southern District; Plovdiv-Marasha; Plovdiv-Gagarin; Plovdiv-Garata). Using mathematical-statistical and analytical methods, we establish spatio-temporal patterns in the distribution of the concentration of PM10 in the air of Plovdiv and determine to what extent the meteorological elements temperature, atmospheric pressure, humidity, wind direction, and wind speed influence this distribution. In order to reveal the intra-annual distribution of FPH10 content, the daily average concentrations of FPH10 in the air of Plovdiv were calculated for each month of the year of the study period 2022-2023. From the data in this table, we compiled statistics for 730 days of both years which can be viewed in Table 1: Statistics. In the statistical analysis, an inverse relationship was observed between temperature and PM10 and PM2.5 content (Figure 6). This correlation is often explained by meteorological factors and human activities, such as the following:  
* Inversions in the atmosphere that keep pollutants close to the ground at low temperatures;
* Increase in heating fuels in winter (especially solid fuel or wood);
* Reduced ventilation in urban areas due to stagnant air. It is important to note that the relationship between temperature and PM can vary depending on local conditions and pollution sources. The relationship between relative humidity (RH) and PM10 (Figure 7) content can be described as a positive correlation under certain conditions, for example,  
1. Condensation of water molecules on dust particles. This increases their size and mass, resulting in higher measured PM10 concentrations. 2. Atmospheric stability: High humidity is often associated with stagnant air, which makes it difficult for dust particles to disperse.