## 5 Conclusions  
This study showed that mist spraying could effectively condense and deposit PM during high PM episodes. YCF and CRP were observed to exhibit rapid changes in PM concentration during mist spraying. And the changes in PM size after spraying differed by the measurement time. During the morning rush hour and lunch, high wind speed and low relative humidity conditions might increase the mist mobility and the combination of the mist and PM, increasing the PM from 2.5 to 10 \(\upmu\)m and hastening the deposition of these PM. During the evening rush hour, low wind speed and high relative humidity conditions seemed to inhibit mist movement, causing this microclimate condition to have a greater effect on PM concentration than that of the mist. Thus, it is necessary to consider the weather conditions when spraying the mist to improve its influence. In contrast, there were no changes in microclimate conditions due to mist spraying.  
Previous conventional mist devices can induce the detrimental effect of leaf burn by intense, focused sunlight in summer, but this mist spraying might lower the leaf burn damage by water vapor. The findings of this study will serve as basic data for applying the effects of the mist generator to reduce PM and tree damage during high PM episodes. However, this study has a limitation on consistent experimental results, owing to various external weather conditions over a short period. In future studies, it will be necessary to analyze the size and growth rate of PM to accurately identify the PM reduction process for mist generators. Based on this, long-term monitoring of microclimate conditions should be conducted to increase the utilization of mist generators to improve the growth environment of trees. Mist spraying can provide an alternative management tool to reduce PM in urban forests during high episodes. This device can be practically applied in an open space of small gardens, street trees, and backyard gardens to diminish leaf burn damage by water droplets during sunny days. This prototype of mist spraying should be more developed and adapted to the field conditions in urban forests with in-depth research between microclimatic conditions and PM growth reductions in the near future.  
Finally, we can suggest the main findings of this study as follows:  
* Mist spraying had significant effects on the concentration of PMx and the ratio of PM during a short time.
* This prototype of mist spraying could effectively condense and deposit the PM during high PM episodes.
* This device can be practically applied in an outdoor environment to diminish leaf burn damage by water droplets during sunny days.  
Conceptualization, methodology, formal analysis, investigation, writing--original draft, writing--review and editing, visualization: S.-Y.Y.; methodology, formal analysis: T.K.; conceptualization, methodology, formal analysis, investigation, project administration: S.C.; conceptualization, methodology, validation, writing--review and editing, supervision, project administration: C.-R.P.; conceptualization, methodology: D.-H.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding, it was internally funded by the National Institute of Forest Science of Korea, grant number NIFOS FE0000201801, and the Korea Forestry Promotion Institute, grant number 2022429B10-2224-0802 (Field test of ultra-fine dust reduction system).