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

Figures & data

Figure 1. Atmospheric particulate matter (PM) and weather data during the data collection period. (a) Mean concentration of atmospheric PM, (b) Sum of PM inflow, (c) Mean ratio of PM_2.5 to PM₁₀, (d) Mean rainfall and wind speed data.

Table 1. Sampling dates, particulate matter (PM) data, and weather data during the experimental period in 2019.

Sampling date (data collection period)	Mean PM concentration (μg/m^3)		Sum of PM inflow (μg/m^2·s)		Mean wind speed (m/s)	Mean rainfall (mm/h)
	PM10	PM2.5	PM10	PM2.5
May 7	61.9	30.3	45545.6	21182.4	2.1	0.05
(Apr 22–May 7)
May 20	63.1	35.0	36686.8	18655.1	1.9	0.08
(May 8–May 20)
May 30	64.6	32.9	34754.6	16537.9	2.4	0.02
(May 21–May 30)
Jun 13	39.3	23.4	26416.4	15297.8	2.1	0.18
(May 31–Jun 13)
Jun 27	29.0	17.2	18746.1	10793.8	2.0	0.04
(Jun 14–Jun 27)
Jul 15	26.5	18.5	24787.4	16161.6	2.4	0.13
(Jun 28–Jul 15)
Jul 17	47.8	39.0	2406.7	1938.5	1.1	0.32
(Jul 16–Jul 17)
Jul 29	23.8	16.7	12680.2	8017.8	2.0	0.45
(Jul 18–Jul 29)
Aug 20	20.3	10.7	19794.5	9969.4	1.9	0.40
(Jul 30–Aug 20)
Sep 2	26.3	14.4	13938.8	7445.2	1.7	0.17
(Aug 21–Sep 2)
Sep 17	17.3	7.5	10916.0	3967.7	2.0	0.35
(Sep 3–Sep 17)
Oct 10	26.7	12.1	20159.6	8482.8	1.5	0.09
(Sep 18–Oct 10)
Oct 23	26.4	13.4	10161.3	4599.5	1.4	0.00
(Oct 11–Oct 23)

PM₁₀ refers to particulate matter with a diameter less than 10 µm, PM_2.5 refers to particulate matter with a diameter less than 2.5 µm.

The sum of the PM inflow was calculated as the sum of the mean hourly PM concentration multiplied by the mean hourly wind speed.

Mean wind speed and mean rainfall are based on mean hourly data.

Figure 2. Hourly rainfall during the study period.

Table 2. Leaf surface morphological traits (data from Je et al. (2020) and Son et al. (2021), mean ± SD).

Traits				Metasequoia glyptostroboides	Prunus yedoensis	Zelkova serrata	Spirea prunifolia f. simpliciflora
Leaf area (cm^2)				18.9 ± 4.4	45.9 ± 8.0	28.9 ± 5.6	6.4 ± 1.0
Roughness (μm)		adaxial		3.9 ± 1.3	3.8 ± 0.3	0.9 ± 0.1	1.4 ± 0.2
		abaxial		3.3 ± 0.4	4.1 ± 0.3	0.6 ± 0.2	1.4 ± 0.3
Trichome	Length (μm)	adaxial		–	–	159.3 ± 86.7	82.8 ± 38.6
		abaxial		–	367.6 ± 75.6	153.5 ± 83.2	391.1 ± 148.4
	Density (no./mm^2)	adaxial	main vein	–	–	92.6 ± 46.0	78.6 ± 19.5
			lateral vein	–	–	100.5 ± 20.7	–
			blade	–	–	12.1 ± 4.9	–
		abaxial	main vein	–	53.8 ± 7.7	112.4 ± 24.9	36.7 ± 21.9
			lateral vein	–	38.0 ± 23.4	112.1 ± 24.2	33.6 ± 19.7
			blade	–	–	17.5 ± 2.4	0.5 ± 0.3
Stomata	Length (μm)	abaxial		22.9 ± 11.7	12.0 ± 4.1	17.3 ± 3.8	7.2 ± 2.3
	Density (no./mm^2)	abaxial		233.2	524.0 ± 51.9	346.5 ± 48.3	913.6 ± 195.0

Table 3. The mass of surface particulate matter with a diameter less than 10 µm (PM₁₀) accumulated on leaves in 2019.

Sampling date	Mass of surface PM10 per unit leaf area (mg/m^2)
	Metasequoia glyptostroboides			Prunus yedoensis			Zelkova serrata			Spirea prunifolia f. simpliciflora
May 7	119.5 ± 64.6 a A			78.9 ± 39.1 a A			82.0 ± 37.5 a A			78.7 ± 29.1 a A
May 20	28.6 ± 15.2 ab AB			21.1 ± 4.7 ab AB			60.2 ± 25.3 a A			19.2 ± 13.9 b A
May 30	42.7 ± 32.4 ab AB			27.9 ± 8.0 b AB			97.8 ± 35.0 a A			58.4 ± 17.7 ab A
Jun 13	36.2 ± 20.1 ab AB			21.3 ± 4.1 b AB			56.6 ± 18.6 ab A			84.9 ± 24.4 a A
Jun 27	54.4 ± 41.6 ab AB			35.8 ± 18.0 b AB			66.6 ± 19.8 ab A			105.2 ± 54.2 a A
Jul 15	40.9 ± 15.4 a AB			31.5 ± 5.7 a AB			31.8 ± 6.2 a A			60.9 ± 20.2 a A
Jul 17	30.4 ± 12.2 a AB			22.8 ± 8.6 a AB			30.7 ± 7.4 a A			44.0 ± 6.8 a A
Jul 29	22.6 ± 11.0 a AB			20.5 ± 6.5 a AB			39.2 ± 25.6 a A			61.7 ± 16.2 a A
Aug 20	30.6 ± 18.1 ab AB			25.7 ± 5.7 b AB			48.5 ± 28.2 ab A			120.9 ± 14.8 a A
Sep 2	34.2 ± 9.9 b AB			35.7 ± 8.0 ab A			101.2 ± 61.4 a A			46.1 ± 14.7 ab A
Sep 17	18.1 ± 7.6 ab B			10.6 ± 3.0 b B			29.2 ± 19.3 ab A			53.4 ± 13.0 a A
Oct 10	26.8 ± 10.2 ab AB			15.6 ± 5.9 b B			72.1 ± 74.9 ab A			73.3 ± 41.9 a A
Oct 23	80.1 ± 15.5 a A			19.3 ± 5.9 b AB			42.5 ± 24.8 ab A			78.3 ± 33.8 a A
Mean	43.5 ± 35.8 b			28.2 ± 20.3 c			58.3 ± 39.5 a			68.1 ± 34.7 a

n = 4 (S. prunifolia f. simpliciflora), n = 5 (all others), mean ± SD.

Different small letters in the same row and different capital letters in the same column indicate significant differences at p < 0.05, according to the Bonferroni correction method after the Kruskal-Wallis test.

Figure 3. The mass of surface particulate matter (PM) per unit leaf area of four tree species. (a) PM₁₀, with a diameter less than 10 µm, (b) PM_2.5, with a diameter less than 2.5 µm.

Table 4. The mass of surface particulate matter with a diameter less than 2.5 µm (PM_2.5) accumulated on leaves in 2019.

Sampling date	Mass of surface PM2.5 per unit leaf area (mg/m^2)
	Metasequoia glyptostroboides			Prunus yedoensis			Zelkova serrata			Spirea prunifolia f. simpliciflora
May 7	22.6 ± 11.2 a A			14.7 ± 7.2 a A			13.7 ± 2.3 a A			19.6 ± 7.9 a A
May 20	2.0 ± 1.4 b B			3.9 ± 1.3 ab AB			12.8 ± 5.8 a A			3.0 ± 3.2 b A
May 30	9.0 ± 5.3 ab AB			7.1 ± 2.0 b AB			18.3 ± 7.6 ab A			23.6 ± 6.8 a A
Jun 13	12.7 ± 3.9 ab AB			7.7 ± 1.4 b AB			18.1 ± 3.4 a A			34.6 ± 3.9 a A
Jun 27	10.8 ± 6 ab AB			8.0 ± 3.2 b AB			12.1 ± 3.8 ab A			30.7 ± 13.0 a A
Jul 15	6.0 ± 1.2 a AB			3.8 ± 1.7 a AB			5.4 ± 0.8 a A			13.4 ± 7.9 a A
Jul 17	3.2 ± 1.9 a AB			4.1 ± 2.4 a AB			4.4 ± 1.5 a A			6.6 ± 4.1 a A
Jul 29	5.5 ± 3.4 a AB			4.3 ± 1.2 a AB			5.7 ± 2.7 a A			15.2 ± 3.3 a A
Aug 20	7.8 ± 4.6 b AB			9.9 ± 1.6 ab AB			14.7 ± 10.1 ab A			43.4 ± 6.2 a A
Sep 2	5.5 ± 1.6 b AB			11.1 ± 3.3 ab A			18.1 ± 8.2 a A			4.4 ± 2.6 b A
Sep 17	6.5 ± 2.8 ab AB			2.8 ± 0.6 b B			9.2 ± 4.4 ab A			11.8 ± 2.2 a A
Oct 10	7.3 ± 1.9 ab AB			5.2 ± 2.2 b AB			12.0 ± 9.0 ab A			18.2 ± 2.9 a A
Oct 23	2.9 ± 2.1 ab B			2.1 ± 2.5 b B			5.9 ± 2.8 ab A			11.6 ± 4.7 a A
Mean	7.8 ± 6.6 b			6.5 ± 4.4 b			11.6 ± 7.1 a			18.2 ± 12.9 a

n = 4 (S. prunifolia f. simpliciflora), n = 5 (all others), mean ± SD.

Different small letters in the same row and different capital letters in the same column indicate significant differences at p < 0.05, according to the Bonferroni correction method after the Kruskal-Wallis test.

Figure 4. The mean ratio of PM_2.5 to PM₁₀ accumulated on the leaves of four tree species.

Table 5. The mean ratio of particulate matter with a diameter less than 2.5 µm to particulate matter with a diameter less than 10 µm for each species during the study period.

	Metasequoia glyptostroboides	Prunus yedoensis	Zelkova serrata	Spirea prunifolia f. simpliciflora
Mean Ratio	0.21 ± 0.12 a	0.24 ± 0.10 b	0.21 ± 0.08 a	0.26 ± 0.12 b

n = 4 (S. prunifolia f. simpliciflora), n = 5 (all others), mean ± SD.

Different letters indicate significant differences at p < 0.05, according to Dunn’s test after the Kruskal-Wallis rank sum test.

Table 6. The mass of particulate matter (PM) with a diameter less than 10 µm (PM₁₀) and a diameter less than 2.5 µm (PM_2.5) accumulated on leaves before (on 15 July 2019) and after (on 17 July 2019) rainfall event.

Type of PM	Sampling date	Mean mass of surface PM per unit leaf area (mg/m^2)
		Metasequoia glyptostroboides	Prunus yedoensis	Zelkova serrata	Spirea prunifolia f. simpliciflora
PM10	Before rainfall	40.9 ± 15.4	31.5 ± 5.7^a	31.8 ± 6.2	60.9 ± 20.2
	After rainfall	30.4 ± 12.2	22.8 ± 8.6^b	30.7 ± 7.4	44.0 ± 6.8
	Mean reduction rate (%)	20 ± 38	29 ± 17	1 ± 27	21 ± 26
PM2.5	Before rainfall	6.0 ± 1.2^a	3.8 ± 1.7	5.4 ± 0.8	13.4 ± 7.9
	After rainfall	3.2 ± 1.9^b	4.1 ± 2.4	4.4 ± 1.5	6.6 ± 4.1
	Mean reduction rate (%)	45 ± 36	–12 ± 42	16 ± 31	–2 ± 132

n = 4 (S. prunifolia f. simpliciflora), n = 5 (all others), mean ± SD.

Mean reduction rate is mean of five PM reduction rates of individual trees before and after rainfall event.

Different letters indicate significant differences at p < 0.05 according to Paired t-test.

Je SM, Kwak MJ, Oh CY, Son J, Chang H, Kim I, Cho JH, Woo SY. 2020. The microstructure of leaves to investigate the mechanism of trees reducing atmospheric particulate matter I (In Korean). Seoul, Republic of Korea: National Institute of Forest Science; p. 128.

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Son J, Chang H, Cho JH, Je SM, Woo SY, Kwak MJ, Lee JK, Chung SK. 2021. The microstructure of leaves to investigate the mechanism of trees reducing atmospheric particulate matter II (in Korean). Seoul, Republic of Korea: National Institute of Forest Science; p. 230.

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