Table 1.

Factor analysis using varimax rotation for PM_2.5 tracer elements.

	Factor (main sources)
Tracer elements of PM2.5	Biomass burning	Industrial	Automotive	Communalities
Si	0.876	0.221	0.382	0.911
S	0.509	0.090	0.856	0.889
Cl	0.475	0.051	0.726	0.763
K	0.888	−0.045	0.385	0.898
V	0.295	0.288	0.665	0.973
Fe	0.619	0.671	0.377	0.874
Ni	0.283	0.317	0.686	0.982
Cu	0.256	0.678	0.200	0.910
Zn	0.039	0.836	0.086	0.879
Br	0.610	0.415	0.238	0.813
Pb	−0.089	0.640	−0.004	0.913
Percent variance	59	21	10

The communality expressed for each variable represents the fraction of the respective variable that is explained by the retained factors. In this case, the communalities were typically higher than 82% (PM_2.5). This indicated that the factors could explain most of the data variability.