Characterization of fine particles during the 2014 Asia-Pacific economic cooperation summit: Number concentration, size distribution and sources

Figures & data

Fig. 1. The time series of (a) temperature (T) and relative humidity (RH), (b) wind speed (WS) and wind direction (WD), (c)evolution of PNSD and mean diameter (circles) of the dominant mode, (d) particle number concentrations in different modes and (e) the mass concentration of PM_2.5 and PM₁₀ and visibility during the measurement period. The APEC summit period and six pollution episodes (Ep1–Ep6) are marked for further discussion.

Fig. 2. Average particle (a) number, (b) surface, (c) volume size distribution and (d–h) average mass size distributions of chemical components in PM₁ measured before and during the APEC summit. The median diameters (MD) and GSD for the mass size distributions of chemical components in PM₁ are also shown.

Table 1. Summary of average meteorological parameters, particle matter and gaseous species, PNC in different modes, PSC, particle volume concentration (PVC) and mass concentrations of PM₁ species for the entire study, before and during APEC, and also the change percentages during APEC.

	Entire study	Before APEC	APEC	Change (%)
Meteorological parameters
T (°C)	13.3	14.7	9.7	34.1
RH (%)	45.5	49.8	34.7	30.3
PM (μg/m^3) & Gaseous species (ppb)
PM10	169.3	196.1	102.3	47.8
PM2.5	99.2	117.6	53.3	54.7
NO	35.4	39.0	26.3	32.5
NO2	35.9	39.6	26.5	33.1
SO2	5.3	5.6	4.6	17.3
O3	16.1	15.7	17.3	–10.6
Particle number, surface & volume concentrations
Nucleation (×10^3 cm^−3)	3.1	3.3	2.4	29.5
Aitken(×10^3 cm^−3)	9.0	9.6	7.7	19.1
Accumulation(×10^3 cm^−3)	7.5	8.3	5.4	35.9
Total PNC (×10^3 cm^−3)	19.0	20.4	15.5	24.0
Total PSC((×10^2 μm^2 cm^−3)	12.9	15.0	7.7	48.7
Total PVC(μm^3 cm^−3)	60.5	72.0	31.6	56.1
Chemical species in PM1 (μg/m^3)
Organics	28.4	32.7	18.2	44.3
Nitrate	16.6	20.7	7.1	65.7
Sulphate	8.6	10.9	3.0	72.2
Ammonium	8.0	10.0	3.3	67.0
Chlorine	2.3	2.6	1.5	41.0
BC	5.3	6.0	3.7	37.3

Fig. 3. Diurnal profiles of the total PNC, PNC in different modes and mass concentrations of PM₁ species measured before and during the APEC summit.

Table 2. The PMF revolved factors for particle number concentration (PNC) for the entire study, before and during APEC, and also the change percentages during APEC.

Factors (×10^3 cm^−3)	Entire study	Before APEC	APEC	Change (%)
Traffic 1	2.1	2.4	1.4	40.2
Traffic 2	6.9	7.4	5.9	20.5
Traffic 3	0.9	1.0	0.6	36.7
Cooking	2.1	2.2	2.0	8.0
Combustion 1	4.6	4.7	4.5	4.3
Combustion 2	1.2	1.6	0.3	82.7
Secondary aerosol	0.2	0.2	0.2	−5.9
Regional aerosol	1.5	1.8	0.6	69.7

Fig. 4. Normalized feature profiles for particle number and volume size distribution (left panel) and time series (right panel) of eight PNC factors resolved by the PMF. Also shown in the right panel are the time series of external tracers including black carbon (BC), Chlorine (Cl⁻), O₃, SIA (sulphate + nitrate + ammonium) and two organic aerosol components (cooking (COA) and (BBOA)). The two pie charts show the average source composition of PNC measured before and during the APEC summit, respectively. The correlation coefficients between PNC factors and external tracers measured before and during APEC are also shown in the figure.

Fig. 5. Diurnal profiles of the number concentrations of PNC factors measured before and during the APEC summit.

Table 3. Correlation coefficients between PNC factors source profiles and external tracers.

	Before APEC	APEC
Traffic 1 vs. NO	0.11*	0.41*
Traffic 2 vs. NO2	0.36*	0.60*
Traffic 3 vs. BC	0.44	0.52
Cooking vs. COA	0.94	0.98
Combustion 1 vs. BC	0.28	0.72
Combustion 1 vs. Cl^−	0.34	0.65
Combustion 2 vs. BBOA	0.89	0.80
Secondary aerosol vs. O3	0.95	0.94
Regional aerosol vs. SIA	0.96	0.90

* Correlation coefficients were calculated only in the morning and evening rush hours.

Fig. 6. Temporal evolutions of (a, d) PNSD and mean diameter (white dashed curve), (b, e) particle number concentration (PNC) factors and (c, f) PM₁ species during the pollution episodes on 21–25 October and 2–4 November. The pie charts show (b, e) the average source contribution of PNC and (c, f) the average chemical composition of PM₁ for each stage.

Table 4. The average number concentration of PNC factors and the average mass concentrations of PM₁ species for each stage during pollution episodes before and during APEC (stages EP3_C, G, P, and EP5_C, G, P as marked in Fig. 6).

	EP3_C	EP3_G	EP3_P	EP5_C	EP5_G	EP5_P
PNC Factors (×10^3 cm^−3)
Traffic 1	1.3(8%)*	1.2(6%)	1.1(5%)	47.8(48%)	12.9(13%)	0.5(0%)
Traffic 2	7.5(43%)	5.7(26%)	7.9(32%)	35.5(36%)	53.5(53%)	25.4(25%)
Traffic 3	0.4(2%)	1.5(7%)	1.2(5%)	0.2(0%)	0.6(1%)	5.8(6%)
Cooking	1.5(9%)	2.0(9%)	4.4(18%)	3.5(4%)	11.5(11%)	30.6(31%)
Combustion 1	6.1(35%)	8.5(39%)	1.6(7%)	2.3(2%)	19.2(19%)	30.8(31%)
Combustion 2	0.1(0%)	0.5(2%)	1.8(8%)	0.6(1%)	0.6(1%)	1.5(1%)
Secondary aerosol	0.2(1%)	0.0(0%)	0.2(1%)	10.0(10%)	1.1(1%)	0.3(0%)
Regional aerosol	0.4(2%)	2.3(10%)	6.2(25%)	0.0(0%)	0.6(1%)	5.1(5%)
Chemical species in PM1 (μg/m^3)
Organics	14.3(53%)	30.9(38%)	65.6(35%)	1.6(50%)	13.8(64%)	62.9(52%)
Nitrate	3.5(13%)	17.9(22%)	55.0(29%)	0.1(3%)	3.2(15%)	23.0(19%)
Sulphate	2.4(9%)	10.9(14%)	30.6(16%)	0.9(27%)	0.9(4%)	8.1(7%)
Ammonium	2.3(8%)	9.1(11%)	25.0(13%)	0.2(7%)	1.2(6%)	11.1(9%)
Chlorine	2.0(7%)	4.1(5%)	3.6(2%)	0.0(1%)	0.4(2%)	6.5(5%)
BC	2.6(10%)	7.5(9%)	9.7(5%)	0.3(11%)	2.1(10%)	8.3(7%)

* The source contribution of PNC factors and chemical composition of PM₁ present in bracket.

Fig. 7. Evolution of size distributions of organics, sulphate and nitrate during the pollution episodes on (a) 21–25 October and (b) 2–4 November.

Fig. 8. Average size distributions of particle chemical species (organics, sulphate and nitrate) for each stage during the pollution episodes as marked in Figs. 6 and 7.