# Examining the Amount of Particulate Matter (PM) Emissions in Urban Areas
## 3 Measurement Results  
### Bus Station  
We performed the measurements at the bus station between 6:00 a.m. and 9:00 a.m. At this time, there is the greatest mobility of buses and pedestrians at the station. Buses have their engines off during their stay at the bus station. Due to longer boarding and disembarking of passengers, vehicle drivers turn off their engines. Since all vehicles are powered by diesel combustion engines, this phenomenon is strongly reflected in the concentration of particulate matter emissions. The morning peak at the bus station is at 6-7 a.m. At this time, we observe the largest number of passengers boarding buses, which increases the time it takes for buses to stop at individual platforms. Figure 4 shows the detected values of PM\({}_{2.5}\) and PM\({}_{10}\) particulate matter concentrations at the bus station. From the graph, we can see the increased concentration of particulate matter, especially in the morning hours from 6:00 to 7:00. This is due to the high intensity of buses that served the bus station at that time. In the graph's background, we show the fluctuations in the number of buses at the station. The highest number of vehicles at the station was between 6:30 and 6:45 (27 vehicles). The measured values of particulate matter emissions and the number of buses at the station show correlation. The higher the number of vehicles serving the station, the higher the concentration of particulate matter emissions. The values of PM\({}_{10}\) emissions worsened, especially in the morning between 6:30 and 6:45 when their value rose to 83 \(\upmu\)g/m\({}^{3}\). The average value of PM\({}_{10}\) emissions in the first hour of the survey is at the level of 61 \(\upmu\)g/m\({}^{3}\). According to the Slovak Hydrometeorological Institute, this value corresponds to a deterioration in air quality. PM\({}_{2.5}\) emission values were normal during this measurement. From the graph, it is possible to observe the decrease in emissions of particulate matter from 8:00 a.m. This is due to the reduced number of buses at the station at the end of the morning peak. From such a course of data, when comparing two consecutive series of data, a situation may arise that the increasing number of buses in the monitored time interval will not mean an increase in the concentration of particulate matter. This phenomenon can be caused by several factors. For example, the length of the vehicle standing on the platform, or the emission class of the buses in operation. We then consider the determination index to be relevant, which in other graphs confirms the hypothesis of the impact of the monitored categories of vehicles on the concentration of particulate matter in the air. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Particle Specifications**} \\ \hline Particulate matter channels & PM\({}_{2.5}\)/PM\({}_{10}\) \\ \hline Particle concentrations & 0 \(\ldots\) 2000 \(\upmu\)g/m\({}^{3}\) \\ \hline Resolution & 1 \(\upmu\)g/m\({}^{3}\) \\ \hline \multicolumn{2}{c}{Particle counter specifications} \\ \hline Particle sizes (in micrometers) & 0.3/0.5/1.0/2.5/5.0 and 10 \(\upmu\)m \\ \hline Flow rate & 2.83 L/min \\ \hline Coincidence error & \textless{}5\% at 2,000,000 particles per cubic foot \\ \hline Counting efficiency & 50\% at 0.3 \(\upmu\)m \\ \hline Memory capacity & Stores up to 5000 data sets \\ \hline Counting modes & Cumulative, differential, concentration \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technical parameters of measuring instrument [43]. Table 3 shows the hourly concentrations of particulate matter at the bus station. During the first hour of measurement, we assessed the air quality as deteriorated based on the concentration of PM\({}_{10}\) emissions. The graph in Figure 4, which tracks the increase in the number of vehicles and the production of emissions, supports our conclusions. The increased number of buses serving the bus station at that time is responsible for the increase in emissions concentration.