Table 2. The contents of eight main heavy metal elements in PM_2.5 fine particles.

Metal elements	Contents in membrane filters (μg g–1) (%)	Airborne concentrations (μg m–3) (%)
Aluminum (Al)	1163 (79.5%)	2.14 (60.5%)
Lead (Pb)	169 (11.5%)	0.66 (26%)
Copper (Cu)	113 (7.7%)	0.41 (17.1%)
Manganese (Mn)	31 (2.1%)	0.23 (11.8%)
Arsenic (As)	6 (0.4%)	0.056 (2.2%)
Chromium (Cr)	5 (0.3%)	0.0283 (1.1%)
Cadmium (Cd)	2 (0.14%)	0.0065 (0.26%)
Nickel (Ni)	0.5 (0.03%)	0.0029 (0.11%)