**1. Introduction**

High domestic PM concentration is known to lead to increased human activity at urban green areas in industrial complex cities. The PM concentration in Korea is usually expressed as the same concentration according to the area where the national atmospheric monitoring station is installed. However, the actual PM values vary, and they change in accordance with the existence of the urban green areas [1,2]. Thus, citizens want to know information about the PM concentration under the forest canopy at hiking time. Urban green area is currently regarded as an important PM reduction measure that is highly accessible to citizens, and it also performs the role of atmospheric purification [3–5]. As a result, urban green area is widely used to manage the urban atmosphere [6,7].

Urban green area can reduce PM by absorption, blocking, and deposition. In the process of photosynthesis, the trees in the green area can absorb gaseous air pollutants such as carbon dioxide (CO2), nitrogen dioxide (NO2), and sulfur dioxide (SO2) through the stomata of the leaves [8]. The tree canopy can also reduce the speed and movement of PM, resulting in PM being blocked and then falling to the surface of the ground [9,10]. Areas with large forest cover ratios were found to have lower PM concentrations than highly urbanized areas [2,7]. However, some studies have reported that the effects of urban green area on the urban atmosphere appear to be limited. The presence of roadside green area interferes with the airflow, causing roadside PM to stagnate and resulting in a higher PM concentration at the roadside green area than at other areas on the roadside [11,12]. The status of PM adsorbed on the leaves could reach the saturation point and block the stoma during the dry winter season [13]. The deposition rate is also sensitive to weather conditions [3,14]. Leaf PM deposition velocity was found to increase with increasing wind speed [15,16], and PM removal rates from the leaf surface were found to be correlated with high rainfall intensity and duration [17]. Therefore, urban green areas have different effects of PM reduction that depend on their structure and the meteorological factors that affect PM movement. It is important to identify the characteristics of PM reduction in urban green areas according to environmental conditions and meteorological factors.

Most studies have focused on identifying the reduction of PM concentration with equations and chamber-based experiments [15–17], so the effects of reducing air pollutants through urban green space need to be verified in the field.

To identify the characteristics of PM reduction in urban green areas, we conducted a study in the buffer green area of the Sihwa Industrial Complex. The research objectives were to determine the effect of urban green area in reducing PM; analyze the relationship between PM, the meteorological factors, and air pollutants; and identify the seasonal patterns of PM reduction by urban green areas.
