Evaluation of black carbon mass concentrations using a miniaturized aethalometer: Intercomparison with a continuous soot monitoring system (COSMOS) and a single-particle soot photometer (SP2)

Figures & data

Figure 1. Flow diagram of the experimental setup.

Figure 2. Correlation between EBC_COSMOS and rBC_SP2 for 1-min (shaded circles) and 15-min average (black circles) datasets. The fitted lines are also shown as bold lines in the corresponding color.

Figure 3. (a) Temporal variation of 15-min averaged ${\mathit{EBC}}_{AE51}^{\mathit{meas}}$ for heated (${\mathit{EBC}}_{AE51,\mathit{htd}}^{\mathit{meas}},$ red line in lower panel) and unheated modes (${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}},$ blue line in lower panel), rBC_SP2 (black line and black filled area in lower and upper panels, respectively), and nonBC_SP2 (shaded filled area in upper panel, cumulated to rBC_SP2) for the entire observation period; (b) as for 3(a) for ${\mathit{EBC}}_{AE51,\mathit{htd}}^{\mathit{meas}},$ ${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}},$ and rBC_SP2 using the same coloring for the period from00:00 14 May to 10:00 15 May, 2017.

Table 1. Proportion of negative values and LOD of the datasets with a 1-min (raw) resolution and averaging for 2-, 5-, and 15-min durations.

Resolution	Proportion of negatives, %	LOD, µg m^−3
Raw	9.1	0.216
2-min average	3.8	0.130
5-min average	1.0	0.093
15-min average	0	0.073

Figure 4. (a) Relationship between ${\mathit{EBC}}_{AE51}^{\mathit{meas}}$ (Y-axis) and rBC_SP2 (X-axis) for the heated (red circles) and unheated (blue circles) modes; (b) as in (a) but for the X-axis (EBC_COSMOS). The fitted lines are also shown in light red for the heated mode and light blue for the unheated mode.

Figure 5. Diurnal variations in ${\mathit{EBC}}_{AE51}^{\mathit{meas}}$/EBC_COSMOS (light-colored lines) and ${\mathit{EBC}}_{AE51}^{\mathit{meas}}$/rBC_SP2 (primary-colored lines) for the heated (red lines) and unheated (blue lines) modes, and nonBC_SP2/rBC_SP2 (black circles, right axis).

Figure 6. (a) Coefficients of determination (r²) and (b) linear regression slopes for the correlations between ${\mathit{EBC}}_{AE51}^{\mathit{meas}}$ and EBC_COSMOS (light-colored lines) and between ${\mathit{EBC}}_{AE51}^{\mathit{meas}}$ and rBC_SP2 (primary-colored lines) for the heated (red lines) and unheated (blue lines) modes as a function of ATN_AE51; (c) as for (b) but with correction using Equations (5)(5) $${{\mathit{EBC}}^{\mathrm{\prime }}}_{AE51,\mathit{unhtd}}^{\mathit{corr}1}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/f_{\mathit{load}}^{\mathit{htd}}.$$(5) and (6)(6) $$f_{\mathit{nonBC}}=Y0-A·\hspace{0.17em}\text{exp}\hspace{0.17em}\left(-B·\frac{{\mathit{nonBC}}_{SP2}}{{\mathit{rBC}}_{SP2}}\right),$$(6) . The averaged nonBC_SP2/rBC _SP2 ratios binned by ATN_AE51 are also shown in (c) as solid lines and closed circles (right axis).

Figure 7. (Left panel) Relationship between ${{\mathit{EBC}}^{\mathrm{\prime }}}_{AE51,\mathit{unhtd}}^{\mathit{corr}1}$/rBC_SP2 and nonBC_SP2/rBC_SP2 (shaded circles). The 7-bin medians (with interquartile ranges) are sorted by nonBC_SP2/rBC_SP2 (open markers). The regression line of the binned datasets is also shown (black line, with the dashed line showing the extrapolation). The fitted coefficients with 95% confidence intervals are also shown; (Right panel) the probability distribution of ${{\mathit{EBC}}^{\mathrm{\prime }}}_{AE51,\mathit{unhtd}}^{\mathit{corr}1}$/rBC_SP2.

Figure 8. Correlations between ${\mathit{EBC}}_{AE51,\mathit{htd}}^{\mathit{meas}}$ corrected using Equation (4)(4) $${\mathit{EBC}}_{AE51,\mathit{htd}}^{\mathit{corr}1}={\mathit{EBC}}_{AE51,\mathit{htd}}^{\mathit{meas}}/f_{\mathit{load}}^{\mathit{htd}}.$$(4) with rBC_SP2 (a) and EBC_COSMOS (b), and between ${\mathit{EBC}}_{AE51,\mathit{htd}}^{\mathit{meas}}$ corrected using Equation (7)(7) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}1}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(C·f_{\mathit{load}}^{\mathit{htd}}\right),$$(7) (shaded circles) and Equation (8)(8) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}2}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(f_{\mathit{load}}^{\mathit{htd}}·f_{\mathit{nonBC}}\right).$$(8) (black circles) with rBC_SP2 (c) and EBC_COSMOS (d). Dashed lines in (a) and (d) are depicted using a ratio of 1:1; (e) and (f) show the cumulative distributions of the ratio of ${\mathit{EBC}}_{AE51,\mathit{htd}}^{\mathit{meas}}$ corrected using Equation (7)(7) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}1}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(C·f_{\mathit{load}}^{\mathit{htd}}\right),$$(7) (shaded) and Equation (8)(8) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}2}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(f_{\mathit{load}}^{\mathit{htd}}·f_{\mathit{nonBC}}\right).$$(8) (black) with rBC_SP2 and EBC_COSMOS, respectively.

Table 2. Summary of intercomparison between the AE51 and the other instruments.

		Correlation			Ratio
	Mode	slope	intercept	r^2	Avg.	1σ
versus COSMOS	Heated	0.97 ± 0.02	0.02 ± 0.01	0.92	1.02	0.17
	Unheated
	corrected by Equation (7)(7) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}1}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(C·f_{\mathit{load}}^{\mathit{htd}}\right),$$(7)	1.04 ± 0.03	0.05 ± 0.01	0.89	1.19	0.23
	corrected by Equation (8)(8) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}2}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(f_{\mathit{load}}^{\mathit{htd}}·f_{\mathit{nonBC}}\right).$$(8)	1.18 ± 0.03	−0.04 ± 0.01	0.93	1.03	0.22
versus SP2	Heated	0.95 ± 0.02	0.03 ± 0.01	0.92	1.03	0.19
	Unheated
	corrected by Equation (7)(7) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}1}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(C·f_{\mathit{load}}^{\mathit{htd}}\right),$$(7)	0.86 ± 0.03	0.10 ± 0.02	0.80	1.17	0.30
	corrected by Equation (8)(8) $${\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{corr}2}={\mathit{EBC}}_{AE51,\mathit{unhtd}}^{\mathit{meas}}/\left(f_{\mathit{load}}^{\mathit{htd}}·f_{\mathit{nonBC}}\right).$$(8)	1.06 ± 0.01	−0.02 ± 0.01	0.97	1.00	0.15

Time resolution = 15 min; values after “±” are the 95% confidence interval of the fitted parameters; the unit of the intercept is μg m⁻³.

Figure 9. Correlations between (a) SP2-derived total aerosols (nonBC_SP2 + rBC_SP2) and PM_2.5 aerosols at four environmental monitoring stations (Black circles = Oppama station; shaded circles = Nagasaka station; shaded squares = Kurihama station; shaded triangles = Honmoku station) and (b) between nonBC_SP2/rBC_SP2 ratios and nonBC_PM2.5 (≡ PM_2.5 - rBC_SP2)/rBC_SP2 ratios at Oppama station. The dashed line in (a) is shown using a ratio of 1:1.