Experimental analysis of PM reduction characteristics between Korean red pine (Pinus densiflora) and sawtooth oak (Quercus acutissima) saplings under different densities and arrangement structures.

As global air pollution, particularly fine particulate matter (PM), has become a major environmental problem, various PM mitigation technologies including green infrastructure have received significant attention. However, owing to spatial constraints on urban greening, there is a lack of management plans for urban forests to efficiently mitigate PM. In this study, we assessed the PM reduction capabilities of Pinus densiflora (Korean red pine) and Quercus acutissima (sawtooth oak) by measuring the changes of PM concentrations using an experimental chamber system. In addition, the PM reduction efficiency in 90 min (PMRE) and the amount of PM reduction per leaf area (PMR) were compared based on arrangement structures and density levels. The results showed that the PM reduction by plants was significantly greater than that of the control experiment without any plants, and an additional reduction effect of approximately 1.38 times was induced by a 1.5 m s air flow. The PMRE of Korean red pine was the highest at medium density. In contrast, the PMRE of sawtooth oak was the highest at high density. The PMR of both species was highest at low densities. The different responses of the species to total reduction were well explained by total leaf area (TLA). The PMRE of both species was positively correlated with TLA. The PMR of sawtooth oak was approximately 2.3 times greater than that of Korean red pine. However, there were no significant differences in both PMRE and PMR between the arrangement structures. Our findings reveal the potential mechanisms of vegetation in reducing PM according to arrangement structure and density. This highlights the importance of efficiently using urban green spaces with spatial constraints on PM mitigation in the future.