Assessment of mobile source air toxics in an Environmental Justice Denver community adjacent to a freeway

Figures & data

Figure 1. Monitoring site locations for Campaigns I and II (left) and Campaign III (right)

Table 1. Site locations and measurements deployed in Campaigns I and II

Site Name	Distance from I-70 (m)	Latitude	Longitude	Elevation (m)	MicroAeth	Carbonyls	Met
1N	17	39.78034	104.9564	1582	x	x
1S	16	39.77983	104.95488	1583	x	x
2N	146	39.78066	104.9561	1582	x	x
2S	127	39.77877	104.9547	1586	x	x
3N	102	39.78111	104.95611	1582	x	x
4N	177	39.78137	104.9554	1582		x	x
5N	177	39.78178	104.9561	1581	x	x

Table 2. Site locations and measurements deployed in Campaign III

Site Name	Distance from I-70 (m)	Latitude	Longitude	Elevation (m)	MicroAeth	VOCs	Met
1S	16	39.779834	104.95488	1583	x	x
1N*	91	39.781	104.9554	1582	x	x	x
2N_a	146	39.781	104.9559	1582	x	x
3N	102	39.7811	104.9561	1582	x	x
2N_b	148	39.7815	104.956	1582	x	x
4N	177	39.7818	104.9561	1582	x	x

Notes. *Site 1N was not at the same location as in Campaigns I and II due to inaccessibility of the location on the school playground during Campaign III.

Table 3. Summary average BC concentrations for Campaigns I and II, segregated by wind direction

		Average BC Concentration (ng/m^3)
Site	Distance (m) from I-70	Winds from the South	Parallel Winds	Winds from the North	All Wind Directions
1S	16	1946	1842^a	1944	1916^a
2S	127	1646	1271	1496	1490
1N*	17	2133^c	1581	1340	1694^b
3N	102	2191^c	1481	1229	1644
5N	177	2031^c	1292	1190	1519

Notes. ^aThe distribution of concentrations for Site 1 S was significantly higher at the 95% confidence level than for all other sites.

^bThe distribution of concentrations for Site 1N was significantly higher at the 95% confidence level than for Site 2S and Site 5N.

^cThe distribution of concentrations for Sites 1N, 3N, and 5N were all higher than for Sites 1S and 2S at the 95% confidence level.

Table 4. Summary average BC concentrations for Campaign III, segregated by wind direction

		Average BC Concentration (ng/m^3)
Site	Distance (m) from I-70	Winds from the South	Parallel Winds	Winds from the North	All Wind Directions
1S	16	1390^a	1586^a	1798^a	1578^a
1N	91	1970	1197	1006	1483
2N	146	2065	1216	1004	1436
3N	102	1610	1051	903	1254^b
4N	177	1727	1072	949	1334

Notes. ^aThe distribution of concentrations for Site 1S was significantly higher at the 95% confidence level than for all other sites when winds blew from the north, were parallel, and under All Wind Directions. It was statistically significantly lower when winds blew from the south.

^bThe distribution of concentrations for Site 3N was significantly lower at the 95% confidence level than for Site 1S and 1N.

Figure 2. Campaign I and II gradients in hourly average binned BC concentrations (ng/m³) measured by microAeths when winds are from the north (top), parallel (middle), and south (bottom)

Figure 3. Campaign III gradients in hourly average binned BC concentrations (ng/m³) measured by microAeths when winds are from the north (top), parallel (middle), and south (bottom)

Figure 4. Enrichment ratio scatter plots of (top, left) benzene and n-pentane divided by propane, (top, right) benzene and 2,2,4-trimethylpentane divided by propane, and (bottom, left) benzene and i-butane divided by propane. All figures are colored by wind direction bins, and sites are indicated by different shapes

Table 5. Factors identified and key pollutants used to classify emissions sources in PMF

Factor	Factor Name	Key Pollutants in Factor
Factor 1	Mobile Source	Acetylene, ethene, toluene, 2,2,4-trimethylpentane, xylenes
Factor 2	Background	Carbon tetrachloride, Freons
Factor 3	Short-Chain Alkanes	Ethane, propane, n-butane, i-butane, n-pentane

Figure 5. Percent of pollutants identified in each factor with a 3-factor PMF solution excluding isoprene

Figure 6. Predicted 24-hour averages of benzene concentrations during the month of January 2018 (top) or July 2018 (bottom) and the observed benzene measurements (24-hour averages) collected from September 15 through October 28, 2018. The values on the map are shown as: Model (Monitor)