**5. Conclusions**

This study investigated the PM-reducing effect of an urban green area in the Sihwa Industrial Complex. Monthly PM reduction was related to the atmospheric mixing height and west wind blowing. Hourly PM reduction was affected by the speed and direction of wind and the vehicle traffic volumes. Thus, the reduction of PM by the urban green area was associated with PM absorption, adsorption and deposition on leaves, monthly mixing height, and the large scale of air current movement affecting air stagnation and PM dispersion. Our results suggest that an urban green area will reduce PM concentration if the forest layer of the urban green area is planted at a proper location, with changes made as necessary, and the operation of industries and vehicles is managed. However, this study only identified the PM-reducing effect of an urban green area based in a limited space,

namely Sihwa Industrial Complex, and analyzed the measured data just for a short period of time. Furthermore, we did not measure PM without an urban green area to confirm the real PM reduction effect of the urban green area. Further research on PM measurement at a control site is required, and it is necessary to identify the overall seasonal PM reduction characteristics through long-term monitoring. Moreover, as the wind condition significantly influences the urban green area's PM reduction effect, further research of prevailing wind field modeling at spatial boundaries on a city level should be carried out to address local solutions for reducing PM concentration.

**Author Contributions:** Collecting the field data and writing the paper, S.-Y.Y.; collecting the field data and analyzing the statistical data on meteorological factors and pollutants, T.K. and S.H.; managing the research project and contributing to the discussion of wind fields and urban green areas, S.C.; designing the study site and measuring equipment and statistical analyses of all data, C.-R.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** This study was funded by National Institute of Forest Science of Korea, grant number NIFOS FE0000201801.

**Conflicts of Interest:** The authors declare no conflict of interest.
