Trace element concentrations in ambient air as a function of distance from road

Figures & data

Table 1. Characteristics of ambient air samples

	n	%
Total elements detected	28
Elements analyzed
Fine	19	67.9
Coarse	22	78.6
Roads Sampled	28
A1	10	35.7
A2	7	25.0
A3	11	39.3
Seasons
Warm	16	57.1
Cold	12	42.9

Table 2. Mean particle mass or concentration and standard deviation values for each element above analyzed in coarse and fine particulate matter (PM). *Element not included in the data analysis because less than 60% of samples had sample concentration greater than sample uncertainty

	Coarse			Fine
Element	Mean ($n$g/m^3)		SD	Mean ($n$g/m^3)	SD
PM	6,000		4,000	9,000	5,000
Na	86.2		179	91.4	153
Mg	30.0		29.2	33.6	33.2
Al	156		149	186	169
Si	368		360	170	208
S	32.8		25.9	373	365
Cl	154		415	82.6	244
K	64.8		56.2	55.9	44.1
Ca	150		201	75.6	15.6
Ti	18.0		22.0	12.4	12.5
V	0.528		0.878	na
Cr	0.551		0.716	10.9	19.6
Mn	3.58		3.80	4.39	4.01
Fe	219		263	205	193
Co	0.429		0.623	na
Ni	na			3.97	7.61
Cu	5.99		9.82	9.25	7.92
Zn	5.54		5.59	27.8	24.9
Br	0.500		0.866	2.72	2.13
Sr	1.26		1.34	2.67	2.03
Zr	2.78		4.92	*	-
Sn	1.74		2.21	6.84	7.30
Ba	11.6		24.3	*	-
Pb	1.14		0.937	5.23	4.59

Table 3. Log distance coefficients for traffic-related pollutants and estimated standard errors (SE), adjusted for season. *Element not included in the data analysis because less than 60% of samples had sample concentration greater than sample uncertainty. Slopes for log distance to road significant at $\alpha =0.05$ shown in bold

	Coarse			Fine
Element	Slope, ${\beta }_{1j}$	SE	p-value	Slope, ${\beta }_{1j}$	SE	p-value
PM	−0.295	0.181	0.104	−0.037	0.018	0.036
Na	−0.260	0.156	0.096	−0.003	0.043	0.951
Mg	−0.200	0.150	0.181	0.007	0.033	0.842
Al	−0.270	0.159	0.091	−0.194	0.046	< 0.001
Si	−0.273	0.165	0.098	−0.033	0.033	0.315
S	−0.275	0.150	0.066	−0.022	0.021	0.283
Cl	−0.307	0.152	0.044	−0.044	0.036	0.209
K	−0.244	0.153	0.111	−0.019	0.023	0.415
Ca	−0.269	0.158	0.090	−0.069	0.028	0.013
Ti	−0.340	0.150	0.023	−0.192	0.035	< 0.001
V	−0.366	0.141	0.010	*
Cr	−0.373	0.135	0.006	−0.222	0.050	< 0.001
Mn	−0.281	0.139	0.043	−0.141	0.052	0.007
Fe	−0.364	0.164	0.027	−0.218	0.032	< 0.001
Co	−0.562	0.165	0.001	*
Ni	*			−0.126	0.075	0.092
Cu	−0.420	0.143	0.003	−0.160	0.029	< 0.001
Zn	−0.319	0.140	0.023	−0.144	0.035	<0.001
Br	−0.199	0.153	0.194	−0.028	0.0549	0.609
Sr	−0.270	0.134	0.043	0.056	0.043	0.196
Zr	−0.560	0.139	<0.001	*
Sn	−0.308	0.147	0.036	0.028	0.061	0.651
Ba	−0.502	0.179	0.005	*
Pb	−0.267	0.138	0.053	−0.055	0.050	0.269

Table 4. Log distance coefficient in the basic model adjusted for season compared to the coefficient in the model additionally adjusted for wind variables. Results are only shown for elements that were significantly associated with wind variables. Slopes for log distance to road significant at $\alpha =0.05$ shown in bold

	Coarse		Fine
Element	Slope, ${\beta }_{1j}$ Basic Model	+ Wind Speed	Slope, ${\beta }_{1j}$ Basic Model	+ Wind Speed	+ Wind Direction
PM	−0.295	−0.293	−0.037	−0.027
Na			−0.003		−0.041
Mg	−0.200	−0.197
Al	−0.270	−0.261
Si	−0.273	−0.265
S	−0.275	−0.278	−0.022	−0.008
K	−0.244	−0.241	−0.019	−0.007
Ca	−0.269	−0.267	−0.069	−0.050
Ti	−0.340	−0.343
V	−0.366	−0.387
Cr			−0.222		−0.246
Mn	−0.281	−0.277
Fe	−0.364	−0.366
Ni			−0.126		−0.159
Cu	−0.420	−0.431
Zn	−0.319	−0.321	−0.144	−0.134
Br	−0.199	−0.268	−0.028		−0.028
Sr	−0.270	−0.268
Zr	−0.560	−0.582
Sn	−0.308	−0.310
Ba	−0.502	−0.497
Pb	−0.267	−0.282