*3.1. Monthly PM Concentration and PM Reduction Rate*

We analyzed the monthly PM concentration, excluding PM data in July when the humidity exceeded 80%. Regardless of PM measuring points, the highest PM<sup>10</sup> and PM2.5 concentrations were observed in May, with values of 99.7 µg/m<sup>3</sup> and 75.9 µg/m<sup>3</sup> , respectively (Figure 2a). During the measuring period, the average PM<sup>10</sup> and PM2.5 concentrations were shown to be at bad levels (daily mean PM10, 80–150 µg/m<sup>3</sup> ; daily mean PM2.5, 35–75 µg/m<sup>3</sup> ) in May, while they were observed to be at normal levels (daily mean PM10, 30–80 µg/m<sup>3</sup> ; daily mean PM2.5, 15–35 µg/m<sup>3</sup> ) in April. Thus, the difference between April and May values was high, even though these measurements were collected in the same season. After May, PM levels gradually decreased, with the lowest concentration being observed in August. In September, PM levels began to increase again. Large deviations of PM<sup>10</sup> and PM2.5 concentrations were observed in the spring, meaning that high PM concentration occurred frequently during that time. On the other hand, summer and fall showed a low deviation of PM concentration, indicating that PM levels were maintained relatively constant compared to spring. Furthermore, no significant differences in PM concentration levels were shown in April, May, and June between the measuring points (Figure 2a). Except for these months, high PM levels were shown, following the order of IC, UG, and RA. In August, monthly PM<sup>10</sup> and PM2.5 reduction rates were high, with values of 44.3% and 56.4%, respectively. The monthly PM<sup>10</sup> and PM2.5 reduction rates in October were high as well, reaching 43.5% and 54.2%, respectively. The lowest PM reduction rates were observed in June (Figure 2b).

**Figure 2.** (**a**) Monthly PM concentration (µg/m<sup>3</sup> ) at measuring points. (**b**) Monthly PM reduction rate (%). Different lowercase letters indicate significant difference between measuring points at a 5% level. Different uppercase letters indicate significant difference between months at a 5% level. IC: industrial complex; UG: urban green area; RA: residential area.
