Urban impacts on regional carbonaceous aerosols: Case study in central Texas

Figures & data

Figure 1. Forty-eight-hour back-trajectory plots showing the path of air arriving at Riesel, TX. Spring is shown in red, summer in green, fall in purple, and winter in blue.

Table 1. Comparison of fine particulate matter (PM_2.5), organic carbon (OC), elemental carbon (EC), and EC/OC ratios for four sampling sites across Texas for 2011 and 2012

	Riesel (2011 and 2012)	Waco (2011 and 2012)	Houston Clinton (2011)				Dallas Hinton (2011 and 2012)
Season	PM2.5 (μg m^−3)	PM2.5 (μg m^−3)	PM2.5 (μg m^−3)	OC (μg m^−3)	EC (μg m^−3)	EC/OC ratio	PM2.5 (μg m^−3)	OC (μg m^−3)	EC (μg m^−3)	EC/OC ratio
Spring (13)	6.77	9.78	14.1	3.73	0.67	0.19	11.9	2.26	0.42	0.19
Summer (39)	10.9	10.0	13.4	2.88	0.69	0.27	12.5	2.27	0.38	0.18
Fall (15)	8.50	7.43	10.4	3.58	0.78	0.23	10.6	2.00	0.51	0.25
Winter (18)	7.85	6.79	10.7	3.59	0.81	0.21	11.5	2.28	0.49	0.21

Note: The number of sampling days for each season is shown in parentheses next to each season.

Table 2. Seasonal organic carbon (OC), elemental carbon (EC), organic mass (OM), EC/OC ratio, water-soluble organic carbon (WSOC), and WSOC/OC ratio concentrations for Riesel, TX, for the 15-month sampling campaign from May 2011 to August 2012

Season	OC (μg m^−3) ± SD	EC (μg m^−3) ± SD	OM (μg m^−3) ± SD	EC/OC ratio	WSOC ± SD	WSOC/OC ratio
Spring (13)	1.9 ± 0.73	0.17 ± 0.04	3.4 ± 0.74	0.09	1.3 ± 0.55	0.66
Summer (39)	3.0 ± 1.6	0.14 ± 0.07	5.3 ± 1.6	0.05	2.0 ± 1.3	0.66
Fall (15)	2.9 ± 2.4	0.22 ± 0.14	5.2 ± 2.4	0.08	1.9 ± 1.6	0.64
Winter (18)	2.3 ± 1.3	0.22 ± 0.09	4.2 ± 1.3	0.10	1.3 ± 0.76	0.55

Note: The number of sampling days for each season is shown in parentheses next to each season.

Figure 2. Contributions of water-insoluble organic carbon (WIOC), water-soluble organic carbon (WSOC), and elemental carbon by season at Riesel, TX. Average MAC and WSOC MAE₃₆₅*10 values are also presented. The WSOC MAE₃₆₅ is not available for spring.

Table 3. Seasonal averages of elemental carbon light attenuation (EC ATN), elemental carbon mass absorption efficiency (EC MAC), water-soluble organic carbon ATN (WSOC ATN), absorption coefficients of WSOC extracts(WSOC b_abs), and mass absorption efficiency at 365 nm (WSOC MAE₃₆₅) of WSOC extracts

Season	EC ATN ± SD	EC MAC (m^2 g^−1) ± SD	WSOC ATN ± SD	WSOC babs(Mm^−1) ± SD	WSOC MAE365 (m^2 g^−1)
Spring	0.22 ± 0.06	9.9 ± 2.7	N/A	N/A	N/A
Summer	0.21 ± 0.13	11 ± 2.3	0.013 ± 0.05	0.35 ± .11	0.15 ± 0.32
Fall	0.29 ± 0.16	9.2 ± 1.8	0.002 ± 0.002	0.08 ± 0.12	0.05 ± 0.07
Winter	0.32 ± 0.15	9.7 ± 1.0	0.004 ± 0.003	0.17 ± 0.14	0.13 ± 0.09

Note: Spring WSOC ATN, WSOC b_abs, and WSOC MAE₃₆₅ values not available.

Figure 3. Light attenuation vs. filter elemental carbon (EC) loading by season; b[0] is equal to the y-intercept and b[1] is equal to the slope of the regression.

Figure 4. Scatter plots showing the correlation of WSOC b_abs (365 nm) and water-soluble organic carbon (WSOC) for summer and winter at Riesel, TX; b[0] is equal to the y-intercept and b[1] is equal to the slope of the regression.

Figure 5. Example of water-soluble absorption spectra for one summer (08/13/2012) and one winter (02/15/2012) sample from Riesel, TX. The Angstrom absorption exponent of the summer sample was 5.8, and 4.8 for the winter sample.