Determination of Heavy Metal Distribution in PM₁₀ During Asian Dust and Local Pollution Events Using Laser Induced Breakdown Spectroscopy (LIBS)

Figures & data

FIG. 1 A schematic of the current LIBS system.

TABLE 1 Average PM₁₀, SO₂, CO, NO₂, O₃, and wind speed in each event period

Event	Date and time	PM10 (μg/m^3)	SO2 (ppb)	CO (ppb)	NO2 (ppb)	O3 (ppb)	RH (%)	Wind speed (m/s)
AD1	10:00–13:00 (October 19, 2009)	134.0 ± 38.4	2.3 ± 0.5	225.0 ± 50.0	8.3 ± 4.8	29.8 ± 4.5	42.9 ± 1.9	5.3 ± 1.5
AD2	22:00–09:00 (March 15–March 16, 2010)	207.2 ± 97.1	1.8 ± 0.8	669.2 ± 193.2	14.0 ± 2.9	40.2 ± 3.3	56.8 ± 7.4	3.3 ± 0.5
AD3	14:00–00:00 (March 20–March 21, 2010)	647.1 ± 697.6	3.2 ± 1.7	936.4 ± 191.2	17.6 ± 5.9	38.0 ± 10.2	60.5 ± 4.9	3.8 ± 1.4
Local pollution	13:00–21:00 (October 13, 2009)	100.7 ± 10.5	6.9 ± 1.6	614.3 ± 37.8	19.3 ± 9.3	43.8 ± 9.5	64.2 ± 16.0	2.2 ± 0.7
	18:00–02:00 (October 16–October 17, 2009)	114.0 ± 18.9	8.7 ± 6.6	466.7 ± 136.6	41.5 ± 14.0	17.8 ± 17.4	68.7 ± 8.3	1.1 ± 0.9
Nonevent	October 07–October 17, 2009	52.3 ± 18.8	3.3 ± 1.7	349.0 ± 100.9	16.6 ± 6.1	24.9 ± 5.9	55.9 ± 17.8	1.7 ± 1.2
	March 16–March 30, 2010	68.1 ± 43.9	2.5 ± 1.1	592.0 ± 122.1	16.4 ± 7.9	34.6 ± 13.3	54.1 ± 19.3	2.3 ± 1.6

FIG. 2 Comparison of hourly PM₁₀, SO₂, and wind speed in Gwangju, Korea among AD events, local pollution events, and nonevents. (Color figure available online.)

FIG. 3 A backward air trajectory ending at an altitude of 100, 500, and 1000 m above ground level at the sampling point during (a) AD1, (b) AD2, and (c) AD3 events (the shaded area indicates industrial zones). (Color figure available online.)

FIG. 4 Comparison of LIBS emission spectra of particles observed (a) between AD1 event and nonevent and (b) between local pollution event and non-event. (Color figure available online.)

TABLE 2 Average metal concentrations of Al, Ca, Fe, Cr, Pb, and Zn during AD events, local pollution events, and non-events

Events	Al (μg/m^3)	Ca (μg/m^3)	Fe (μg/m^3)	Cr (μg/m^3)	Pb (μg/m^3)	Zn (μg/m^3)
AD1	1.44 ± 0.52	1.62 ± 0.24	2.79 ± 0.43	0.03 ± 0.01	0.28 ± 0.07	1.03 ± 0.27
AD2	0.81 ± 0.53	2.10 ± 1.15	2.35 ± 1.96	0.03 ± 0.02	0.09 ± 0.09	0.25 ± 0.19
AD3	3.63 ± 2.58	4.03 ± 2.10	6.30 ± 5.76	0.04 ± 0.02	0.29 ± 0.23	1.49 ± 0.66
Local pollution event	0.31 ± 0.09	0.24 ± 0.09	1.90 ± 0.85	0.03 ± 0.01	0.29 ± 0.11	0.52 ± 0.28
Non-event	0.24 ± 0.09	0.37 ± 0.20	0.86 ± 0.66	0.02 ± 0.01	0.10 ± 0.07	0.21 ± 0.37

FIG. 5 (a) A relationship between LIBS intensity ratios (Al/C, Ca/C, Fe/C, Cr/C, Pb/C, and Zn/C) and concentrations and (b) a relationship between LIBS intensity ratios normalized by boiling point (T_b ) and upper energy level (ΔE), and concentrations.

FIG. 6 Average concentration of (Cr + Pb + Zn) and PM₁₀-weighted value [(Cr + Pb + Zn)/PM₁₀] during AD and local pollution events. (Color figure available online.)

FIG. 7 Temporal variations of the concentrations of crustal elements and anthropogenic heavy metals during (a) AD2 event and (b) local pollution event on October 13, 2009. (Color figure available online.)

FIG. 8 Score plots of (a) PC1 and PC2 during AD and local pollution events and (b) PC1, PC2, and PC3 among AD events (AD1, AD2, and AD3).