Measurement of the gross alpha activity of the fine fractions of road dust and near-roadway ambient particle matter

Figures & data

Figure 1. Ambient PM_2.5 alpha activity (Bq/mg PM and Bq/m³) and uncertainty measured in samples collected at the roadside and local background positions at major roadways in the greater Boston area

Figure 2. Road dust (RD_2.5) alpha activity (Bq/mg RD) and uncertainty measured in samples collected at the roadside and local background positions at major roadways in the greater Boston area

Table 1. Ratio of ambient PM_2.5 to RD_2.5 alpha activity (Bq/mg)

Position	Air/Dust Alpha Activity Ratio
	Average (SD)*	Minimum	Maximum
Roadside	23.5 (11.0)	1.7	40.8
Background	19.7 (8.7)	9.0	51.7
Overall	21.6 (10.0)	1.7	51.7

Notes. *Ratios are all statistically significant; paired sample t-test for PM_2.5 and RD_2.5 roadside, background and overall yield p-values ≪.001.

Table 2. Fixed effect estimates for ambient PM_2.5 and road dust RD_2.5 alpha activity models

Model	Fixed Effect	Slope	SE	p-value
Ambient PM2.5	Season Cold (Warm = 0)*	0.07434	0.02344	.0037
	Position Background (Roadside = 0)	0.04469	0.02269	.0589
Road Dust (RD2.5)	Zinc*	0.00338	0.00100	.0020
	EC1*	0.00019	0.00005	.0004
	Position Background (Roadside = 0)*	0.00431	0.00136	.0040

Notes. *Statistically significant predictors of alpha activity level in Bq/mg at p < .05.