## 1 Introduction
### Methodology  
In order to understand the emission trend of PM generated in excavation and restoration work, an on-site test bed was established and PM emission was measured while performing the same construction method as the actual construction equipment and processes.  
The representative PM measurement techniques include the gravimetric analysis, beta-ray absorption, light scattering, and digital image information analysis methods as seen in Table 2[31, 32, 33]. In this study, the light scattering method, which is portable and can be measured in real time, was applied to measure the PM instantaneously generated during construction in the field. For the measurement equipment, the GRIMM's optical particle counter (OPC Model EDM164) was used and this equipment was calibrated according to the ISO 21501-4 standard. This OPC can measure particles in the size range of 0.3-35 \(\upmu\)m and measure the PMC of PM\({}_{10}\) and PM\({}_{2.5}\). Data was collected and analyzed every 6 s in real time, and the sample flow rate was 1.2 L/min. Thus, it was determined to be suitable for measuring PM generated from road excavation-restoration work.  
This experiment set PM\({}_{10}\) as the main analysis target and five OPCs were used for measurements. Four OPCs were placed 2 m and 4.25 m away from the construction section (the emission source), and the height of the inlet in the OPC was adjusted to 1.5 m. The OPC for measuring background concentration and the automatic weather station (AWS) for collecting meteorological data were placed close to the construction site (Figure 2a). The activities of road excavation-restoration work were classified into road-cutting, breaking, removal, excavation, and restoration, and PM measurement was carried out for the entire process. Two testbeds were built for field testing. Both test beds consisted of a 20 cm thick  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Data Type** & **Activity Type** & **Instrument Used** & **Size Range (\(\upmu\)m)** & **Location** & **Source** \\ \hline PMC & Asphalt milling & Sampling pumps & 0.1–10 & Outdoor & [25] \\ \hline PNC & Road works & CPC & 0.02–1 & Outdoor & [26] \\ \hline PMC, PNC & Concrete mixing, drilling, cutting & DMA, OPC & 0.005–20 & Indoor & [29] \\ \hline PMC & Concrete grinding & Sampling pumps & 0.1–10 & Indoor & [30] \\ \hline PMC, PNC & Asphalt works &
\begin{tabular}{c} SMPS, CPC, \\ OPC, OPS \\ \end{tabular} & 0.014–10 & Outdoor & [28] \\ \hline PMC & Asphalt works & OPC & 0.3–35 & Outdoor & [27] \\ \hline \end{tabular} Note: PMC, particle mass concentration; PNC, particle number concentration; CPC, condensation particle counter; DMA, differential mobility analyzer; OPC, optical particle counter; SMPS, scanning mobility particle size; OPS, optical particle size.  
\end{table}
Table 1: Summary of past studies related to PM emissions from road-paving construction.  
asphalt pavement layer and a 60 cm thick subgrade layer. The asphalt concrete layer was applied with a hot mix asphalt most commonly used in urban road pavement. Granite aggregate with a maximum aggregate size of 19 mm and an AP-5 grade asphalt binder were used. The first testbed consisted of six sections and the second testbed consisted of two sections. The size of all sections was the same, and the PM emission amount was measured while repeating the same activities in each section. The average value of each measurement data was used for analysis. The working sections of the first and second field experiments are shown in Figure 2b,c, and the measurement conditions are summarized in Table 3.