Source identification and apportionment of fine particulate matter in Houston, TX, using positive matrix factorization

Samples of airborne fine particulate matter were collected at three sites in Houston, TX, and were analyzed for elemental concentrations by X-ray fluorescence and inductively coupled plasma-mass spectrometry. Positive Matrix Factorization (PMF) was applied to the elemental concentration data for source identification and apportionment. PMF resolved five physically interpretable factors at each site, of which four were found to be common at all sites: Crustal material, road dust, wood burning, and sea salt. The composition of the remaining factor was similar, but not identical, at the three sites, and had an elemental composition similar to industrial combustion. Crustal material was found to be the most important contributor at each site. All other sources contributed less to the total mass, although road dust source was the second major contributor to the total mass at one site. The sea salt factor was resolved at each site with the highest contribution at the closest site to the coast.