Table 8.

The potential ecological risk index of heavy metals of dust during winter in Beijing.

Heavy Metal	TC	Urban Dust			Suburban Dust
		PC	${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$	ED	PC	${\mathit{E}}_{\mathit{r}}^{\mathit{i}}$	ED
Cd	30	33	988	Extreme damage	20	599	Extreme damage
Co	5	1	5	No damage	1	5	No damage
Cr	2	3	5	No damage	3	5	No damage
Cu	5	11	56	Moderate damage	6	29	Mild damage
Ni	5	2	11	Mild damage	2	9	No damage
Pb	5	6	30	Mild damage	4	22	Mild damage
V	2	1	2	No damage	1	2	No damage
Zn	1	7	7	No damage	6	6	No damage
RI	-	-	1104	Serious risk	-	678	Serious risk

TC: toxicity coefficient; PC: pollution coefficient; ED: ecological damage.