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. Author manuscript; available in PMC: 2019 Mar 6.
Published in final edited form as: Environ Sci Technol. 2018 Feb 14;52(5):2844–2853. doi: 10.1021/acs.est.7b04889

Table 1.

Summary of Prominent Components of PCA for the Combined Mobile and Fixed-Site Data

component explained
variance (%)		 high loading pollutants likely source
1st 26 low molecular weight hydrocarbons, xylenes, NOx light-duty vehicle
2nd 24 NO2, NOx, CO2, BC, PNfine diesel exhaust
3rd 17 long-chain alkanes, PNintermodal crankcase emissions
4th 16 UFPN, PN1, UFPN − PN1, BC aircraft or other