Analysis of ethylene concentration in the Mexico City atmosphere by photoacoustic spectroscopy

A CO2 laser photoacoustic spectrometer was used to measure the ethylene con centration in air samples taken from the Mexico City atmosphere. Samples we re collected in four different zones: a) Facilities of the Mexican Institut e of Petroleum (IMP), which is located near to Vallejo industrial zone and next to an avenue with high traffic density; b) an industrial zone, charact erised by a high industrial activity and high density of heavy automotive v ehicles (Xalostoc); c) a zone characterised by a strong commercial activity and intense flux of cars and small-size trucks (La Merced); and d) a resid ential zone with low traffic density (Pedregal). At IMP, air sampling was c arried out twice a day, in the morning and in the afternoon, the former sam pling showing higher ethylene concentrations. In the other zones, air sampl ing was carried out simultaneously, between 6:00 and 9:00 a.m., during 5 co nsecutive days in November 1999. The average ethylene concentrations in Xal ostoc, La Merced, and Pedregal were 40.3 ppbV, 37 ppbV, and 18.7 ppbV, resp ectively. These data agreed with results obtained by gas chromatography.