# The Impact of Solid Fuel Residential Boilers Exchange on Particulate Matter Air Pollution
## 3 Results and Discussion
### Vratimov  
The maximum daily PM\({}_{10}\) concentrations remain the same in the total area and urban area of the town. Interestingly, even after the partial exchange of the solid fuel boilers, scenario B (148 out of 511 devices), the maximum daily concentrations remain unchanged. The average daily airborne particle pollution during scenario B dropped by 27.6%. In the case of scenario C with the hypothetical total exchange of boilers, the average daily airborne particle pollution decreased by 91.7%. The highest PM\({}_{10}\) concentrations were observed in the most populated urban areas of the town, with the highest amount of  
Figure 4: Particulate emissions dispersion model for the location Vratimov. solid fuel boilers. The most populated areas are located on the hilly terrain, which might influence the air pollution concentrations. Furthermore, after a partial boiler exchange (scenario B), only 29% of boilers were replaced; thus, the maximum daily concentrations remain locally very high (up to 192 \(\upmu\)g/m\({}^{3}\)) during the heating season. Only after the total boiler replacement, as modelled in scenario C, the maximum PM\({}_{10}\) concentrations rapidly decrease to approximately 12 \(\upmu\)g/m\({}^{3}\). All three locations are located in an outstandingly polluted area of the Moravian-Silesian region. This is a traditional coal-mining region with heavy industry and a relatively high level of urbanization. The average yearly concentrations of PM\({}_{10}\) in the ambient air in this region have not been significantly decreasing in the past years but remain quite high in the range of 30.9 \(\upmu\)g/m\({}^{3}\) in 2016 to 33.8 \(\upmu\)g/m\({}^{3}\) in 2018 [27]. For the comparison of the modelled data of PM\({}_{10}\) concentrations, we conducted a series of PM\({}_{10}\) measurements in Dolni Lhota and Vratimov, using a hi-vol air sampler, during the heating season in 2018 (Figure 5). For the same days, we obtained data from the Czech Hydrometeorological Institute from the Opava-Katerinky station (located approximately 7 km from Kravare). Furthermore, a series of PM\({}_{10}\) measurements were conducted during the smog situation in February 2018 in Dolni Lhota. Nonetheless, even after a partial solid fuel boiler exchange in selected locations, the average daily concentrations of PM\({}_{10}\) still remained high during the heating season. The highest measured average daily concentration of PM\({}_{10}\) was determined for the Kravare site (82.5 \(\upmu\)g/m\({}^{3}\)). Higher PM\({}_{10}\) concentrations were observed during the smog situation in Dolni Lhota, approximately 25% higher than average concentrations throughout non-smog winter days. Typical for the northeast part of the Czech Republic is a predominant airflow from the southwest (mainly during a cyclonic, low-pressure-type of weather) coming from other parts of the Czech Republic, Germany and Austria. Conversely, there is an opposite northeast airflow coming transboundary from Poland with low wind velocities, associated with anticyclonic situations (high-pressure systems), which is often accompanied by worsened dispersion conditions, especially during the cold period of the year. According to a transboundary (Polish-Czech border) air-pollution report, there was both a much higher pollution load and a much higher frequency of days with average PM\({}_{10}\) concentrations above 50 \(\upmu\)g\(\cdot\)m\({}^{-3}\) (daily limit value) and 100 \(\upmu\)g\(\cdot\)m\({}^{-3}\) during days with airflow direction from Poland to the Czech Republic [28]. According to another extensive study  
Figure 5: Boxplot-type comparison of daily average PM\({}_{10}\) concentrations on selected days during the heating season in 2018.  
of air pollution in this area [27], the main cause of PM pollution is individual residential heating.