Hydrocarbon source apportionment in Mexico City using the chemical mass balance receptor model

A field study was conducted in Mexico City during May-November 1997 to dete rmine non-methane hydrocarbons (NMHC) species emitted from different source s: application of slow curing asphalt pavement, liquefied petroleum gas (va pour phase), dry cleaning, graphic arts, landfill, emissions of motor vehic le exhaust inside a tunnel, hot soak, whole gasoline, painting operations a nd degreasing. Forty-five ambient air samples of NMHC were simultaneously c ollected from 6:00 to 9:00 a.m. at three different sites, Xalostoc, Pedrega l and La Merced, denominated receptors, during the spring and fall of 1996. In both cases samples were collected in stainless-steel canisters and anal ysed by gas chromatography with flame ionisation detection system. Based on these measurements the chemical mass receptor model (CMB) was applied to e stimate the contribution of the different NMHC source to ambient pollution. The average results for the two sampling periods showed that the major sou rces of NMHC for the three sites were: motor vehicle exhaust with an averag e contribution of 54.9, 57.4 and 63.8% for Xalostoc, Pedregal and La Merced , respectively, followed by handling and distribution of liquefied petroleu m gas with 28.5% in Xalostoc, 20.0% in Pedregal and 24.0% in La Merced. (C) 2000 Elsevier Science Ltd. All rights reserved.