*2.1. Study Site*

The study site, Sihwa (37◦22′N, 126◦46′E), is a national industrial complex adjacent to the west coast of Korea and consists of steel-, chemical-, and machinery-oriented industries. The main air pollutants of the Sihwa Industrial Complex are NO<sup>2</sup> and SO<sup>2</sup> emissions, which are caused by the operation of vehicles and ships as well as the combustion involved in manufacturing activities during the production process [18]. The Sihwa Industrial Complex has the characteristic of wind blowing in the northwest direction, from the coast to the land. Thus, the buffer green area was established in the 2000s to prevent the spread of air pollutants and odor from the industrial complex to the residential area. The buffer green area is an urban green area located in the center of Sihwa Industrial Complex and New City. The dimensions of this site are 3.46 km (L), 0.18 to 0.25 km (W), and 10 m (H), and it consists of a Japanese black pine (*Pinus thunbergii*) and Japanese red pine (*Pinus densiflora*) community [19]. The densities of the Japanese black pine (*Pinus thunbergii*) and Japanese red pine (*Pinus densiflora*) are 24.5 trees/100 m<sup>2</sup> and 0.75 trees/100 m<sup>2</sup> , respectively. To analyze the PM reduction effect of the urban green area, we selected three PM monitoring points: Somang park in the industrial complex (IC; 37◦20′ N, 126◦43′ E), the urban green area (UG; 37◦20′ N, 126◦43′ E), and Jungang park in the residential area (RA; 37◦20′ N, 126◦44′ E) (Figure 1). The distance between IC and UG is 1 km, and the distance between RA and UG is 0.76 km. As IC is surrounded by various industries and RA is a nearby apartment complex, we considered that these measuring points could reflect the characteristics of PM in each area. IC is dominated by *Pinus strobus* (4.5 trees/100 m<sup>2</sup> ) and *Pseudocydonia sinensis* (0.5 trees/100 m<sup>2</sup> ). RA is made up of *Pinus rigida* (8.75 trees/100 m<sup>2</sup> ) and *Pinus densiflora* (0.5 trees/100 m<sup>2</sup> ).
