Seasonal variations in accumulated particulate matter on leaves of four major tree species in Korea

Abstract Tree planting is a countermeasure used to mitigate the effects of the high concentrations of atmospheric particulate matter (PM), because trees have a strong ability to adsorb PM. However, owing to the limited information on PM accumulation on leaves throughout the year, guidelines for the implementation of urban forests cannot be provided. Therefore, in this study, we measured PM accumulation in leaves to compare the PM-reducing ability of four common species (Metasequoia glyptostroboides, Prunus yedoensis, Spirea prunifolia f. simpliciflora, and Zelkova serrata) during one growing season. We collected leaves almost every two weeks from 7 May to 23 October 2019, in Seoul Forest Park. We then measured the PM quantities on the leaves before and after rainfall (28 mm/h) to determine the amount of PM that washed off. We found that the average PM10 (PM <10 µm in diameter) accumulation on the leaves of S. prunifolia f. simpliciflora, Z. serrata, M. glyptostroboides, and P. yedoensis during one growing season was 68.1, 58.3, 43.5, and 28.2 mg/m2, respectively. The average PM2.5 (PM <3 µm) accumulation on the leaves of S. prunifolia f. simpliciflora, Z. serrata, M. glyptostroboides, and P. yedoensis was 18.2, 11.6, 7.8, and 6.5 mg/m2, respectively. However, the accumulation of both PM10 and PM2.5 on the leaves of the four species fluctuated during the sampling period. The average ratio of PM2.5 to PM10 accumulation in the leaves of S. prunifolia f. simpliciflora and P. yedoensis was significantl higher than that of Z. serrata and M. glyptostroboides; however, this ratio fluctuated throughout the sampling period. Rainfall considerably reduced the levels of PM10 on the leaves of P. yedoensis and PM2.5 on the leaves of M. glyptostroboides. We found no significant removal of PM from the leaves of other species. These results indicated that the PM-reducing ability of trees varies between species and over time. Therefore, urban forests should be managed with a high diversity of tree species.