Table 1.

Source Profile Constraints

Constraint Type	Species	Source				Literature Citationse
		Brake Wear	Tire Wear	Road Salt	Soil(s)
Species Ratio (λt)a	Cu/Sb	3.9 (0.1)b				1-12
	Cu/Ba	1.2 (0.1) b				1-9, 12
	Cu/Fe	0.05 (0.1) b				1-8, 12
	Zn/Pb		1000 (0.1) b			13,14
	Zn/K		24 (0.1) b			13,14
	Zn/Ca		26 (0.1) b			13,14
Upper or Lower Limit Constraints on Average Species Concentration (ng/m3)	Ba	>0.001				1-9, 12
	Cu	>0.001				1-9, 12
	Pb		<0.001			16
	Zn		>0.001			13-15
	Cl			>0.01
	Na			>0.01
	βc				0 (1e-5)c
Maximum Constraint on Q	Si				400d

^asee equation 4 in text;

^b( ) =maximum allowable constraint error;

^cdimensionless value for c not equal to k-2 {see equation 6 in text};

^dmaximum allowable increase of Q for upward pulling of average species concentration using error mode −20 in ME2 {see also equation 5 in text}

^e1. Kennedy and Gadd, 2003; 2. Garg et al, 2000; 3. Iijima et al, 2007; 4. Geitel et al, 2010; 5. Schauer et al, 2006a; 6. Grieshop et al, 2005; 7. Bukoweicki et al, 2010; 8. von Uexkull et al, 2005; 9. Sternbeck et al, 2004; 10. Weckwerth, 2001; 11. Adachi and Tainosho, 2004, 12. Johansson et al, 2009; 13. Apeagyei et al 2011; 14. EPA, 2003; 15. Han et al, 2011. 16. Wahlin, 2006