Experimental analysis of PM 2.5 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 _2.5 ), has become a major environmental problem, various PM _2.5 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 _2.5 . In this study, we assessed the PM _2.5 reduction capabilities of Pinus densiflora (Korean red pine) and Quercus acutissima (sawtooth oak) by measuring the changes of PM _2.5 concentrations using an experimental chamber system. In addition, the PM _2.5 reduction efficiency in 90 min (PMRE ₉₀ ) and the amount of PM _2.5 reduction per leaf area (PMR _LA ) were compared based on arrangement structures and density levels. The results showed that the PM _2.5 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 ^-1 air flow. The PMRE ₉₀ of Korean red pine was the highest at medium density. In contrast, the PMRE ₉₀ of sawtooth oak was the highest at high density. The PMR _LA 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 ₉₀ of both species was positively correlated with TLA. The PMR _LA of sawtooth oak was approximately 2.3 times greater than that of Korean red pine. However, there were no significant differences in both PMRE ₉₀ and PMR _LA between the arrangement structures. Our findings reveal the potential mechanisms of vegetation in reducing PM _2.5 according to arrangement structure and density. This highlights the importance of efficiently using urban green spaces with spatial constraints on PM _2.5 mitigation in the future.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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