## 3 Evaluation of PM\({}_{10}\) Generated in Cutting Operation through Chamber Experiment (Level 2)
### Experimental Results and Analysis  
#### 3.2.1 Scattered PM  
The emission characteristics of scattered PM\({}_{10}\) generated from the asphalt concrete specimen-cutting activity were analyzed by measuring PM using the OPC. The generation process of scattered PM\({}_{10}\) from the asphalt concrete specimen-cutting activities was similar for test IDs 1-4. The PMC and particle number concentration (PNC) of the test ID 1 are shown in Figure 7.  
The measurement of test ID 1 took approximately 10 min, and the cutting activity was performed for approximately 2 min (from 4 to 6 min). In all experiments, PMC and PNC showed a sharp increase immediately after the cutting blade touched the cutting surface. In addition, the dust settled in approximately 2 to 3 min after the work was finished. In all tests, the trends of PMC and PNC were found to be similar. Table 5 shows the average PMCs of PM\({}_{10}\), PM\({}_{2.5}\), and PM\({}_{1}\) according to the cutting depth.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Test ID** & **Depth (mm)** & **PM\({}_{\mathbf{10}}\) (\(\mathbf{\mu}\)g/m\({}^{\mathbf{3}}\))** & **PM\({}_{\mathbf{2.5}}\) (\(\mathbf{\mu}\)g/m\({}^{\mathbf{3}}\))** & **PM\({}_{\mathbf{1}}\) (\(\mathbf{\mu}\)g/m\({}^{\mathbf{3}}\))** \\ \hline
1 (dry) & 50 & 38,069.43 & 4669.73 & 588.71 \\
2 (dry) & 70 & 24,894.83 & 3139.14 & 369.41 \\
3 (dry) & 100 & 18,475.79 & 1455.27 & 147.91 \\
4 (wet) & 100 & 1713.62 & 427.14 & 67.48 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Average PMC values according to cutting depth.  
Figure 7: Scattered dust during cutting (test ID 1). (**a**) PMC and (**b**) PNC.  
First, as a result of testing in dry states, the scattered PM\({}_{10}\) decreased as the cutting depth increased. In the case of test ID 1 (depth 50 mm), PM\({}_{10}\), PM \({}_{2.5}\), and PM\({}_{1}\) yielded PMCs which were approximately 2.1-, 3.2-, and 4-times higher compared with that for test ID 3 (depth 100 mm), respectively. As the cutting depth increased, the scattered PM\({}_{10}\) decreased because the dust was trapped inside the asphalt specimen. In the case of test ID 4 where wet cutting was performed, the PMC of scattered PM\({}_{10}\) decreased by approximately 90.7% compared with test ID 3 where dry cutting was performed under the same conditions.  
The particle number distribution (PND) was analyzed to determine the number of particles (based on their sizes) generated from the cutting activities for PM with sizes in the range of 0.3-35 \(\upmu\)m. The variations of PNDs as a function of the cutting depth are shown in Figure 8. In test IDs 1-4, the proportions of PM\({}_{1}\) were 83.1%, 76.7%, 73.9%, and 84.5%, respectively, thus indicating that PM\({}_{1}\) occupies a large proportion of the total PNC. Moreover, it was found that the particle number of generated PM decreased as the cutting depth increased in every range of particle size.  
As a result of analyzing the OPC measurements, it was found that as the cutting depth increased, not only the particle concentration but also the number of particles scattered due to the cutting activities decreased.  
The weights of PM collected in the 10 \(\upmu\)m internal filter and the 0.3 \(\upmu\)m external filter were measured. The results are listed in Table 6. The weight of PM collected in the filter decreased as a function of the cutting depth. The weights of PM obtained by wet cutting decreased by approximately 93.2% compared with that produced by dry cutting. The analyzed results of PM collected in the filter show the same trend as the mass concentration and number of particles analyzed by the OPC.