Characterization of urban aerosol using aerosol mass spectrometry and proton nuclear magnetic resonance spectroscopy

Particulate matter was measured during August and September of 2006 in Houston as part of the Texas Air Quality Study II Radical and Aerosol Measurement Project. Aerosol size and composition were determined using an Aerodyne quadrupole aerosol mass spectrometer. Aerosol was dominated by sulfate (4.1 ± 2.6 μg m−3) and organic material (5.5 ± 4.0 μg m−3), with contributions of organic material from both primary (∼32%) and secondary (∼68%) sources. Secondary organic aerosol appears to be formed locally. In addition, 29 aerosol filter samples were analyzed using proton nuclear magnetic resonance (1H NMR) spectroscopy to determine relative concentrations of organic functional groups. Houston aerosols are less oxidized than those observed elsewhere, with smaller relative contributions of carbon-oxygen double bonds. These particles do not fit 1H NMR source apportionment fingerprints for identification of secondary, marine, and biomass burning organic aerosol, suggesting that a new fingerprint for highly urbanized and industrially influenced locations be established.

► SOA constitutes approximately 2/3 of organic aerosol loadings in Houston.
► Data indicate a water insoluble fraction of oxidized organic aerosol.
► Aerosol WSOC is less oxidized and does not fit previously identified 1H NMR source fingerprints.