The utilization of urban green areas has increased, but it is unclear whether urban green areas can decrease the concentration of particulate matter at an industrial complex city in Korea. We measured the extent of particulate matter (PM) reduction at a buffer green area in the Sihwa Industrial Complex. PM was measured at the industrial complex, the urban green area, and a nearby residential area from April to October 2019. PM reduction rates were highest at the urban green area in August and October, which is related to increased atmospheric mixing height and the active west wind blowing from the industrial complex to the residential area. Reduction rates of PM10 and PM2.5 at the urban green area showed the lowest values, namely 14.4% and 25.3%, respectively. The air temperature, wind speed, and humidity could affect the PM reduction rate by influencing the movement and dispersion of PM at the micro-spatiotemporal scale. These results indicated that PM concentration could be reduced by the structural change of a forest layer at a micro scale in urban green areas.

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A mist generator is designed to prevent particulate matter (PM) damage to trees by reducing PM by combining mist and PM during high PM episodes. In addition, mist can minimize the dry heat damage caused by high temperatures and low relative humidity during high PM episodes. Herein, we tested the effects of PM reduction and microclimate condition change with mist generators in urban forests with high PM episodes. We measured changes in microclimate conditions and the concentration of PM before, during, and after mist spraying in urban parks (Yangjae Citizen Forest, YCF; Cheongdam Road Park, CRP) from May 6 to 8, 2020. PM changes in YCF and CRP were observed immediately after mist spraying and were found to return to the previous concentrations. At the morning rush hour and lunch, mist, high wind speed, and low relative humidity conditions were related to the increase of the mist movement, resulting in increasing PM (2.5–10 µm) and the deposition of these PM. During the evening rush hour, high relative humidity and low wind speed affected PM concentrations more than mist. However, no significant differences were observed in the microclimate conditions after mist spraying. Despite these preliminary results, these findings indicate that mist may reduce PM and PM damage to trees during high PM episodes.