An application of mist generator as a way to reduce particulate matter during high concentration episodes at urban forests

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.