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TheScientificWorldJOURNAL
Volume 2, Pages 844-860
http://dx.doi.org/10.1100/tsw.2002.147
Research Article

Receptor Model Source Apportionment of Nonmethane Hydrocarbons in Mexico City

1Universidad Autónoma Metropolitana-Azcapotzalco. Av. San Pablo No. 180, Col. Reynosa Tamaulipas Azcapotzalco, 2200 México, DF., Mexico
2Desert Research Institute, Reno, NV, USA
3Instituto Mexicano del Petróleo, México D.F., Mexico

Received 18 October 2001; Revised 24 January 2002; Accepted 29 January 2002

Copyright © 2002 V. Mugica et al.

Abstract

With the purpose of estimating the source contributions of nonmethane hydrocarbons (NMHC) to the atmosphere at three different sites in the Mexico City Metropolitan Area, 92 ambient air samples were measured from February 23 to March 22 of 1997. Light- and heavy-duty vehicular profiles were determined to differentiate the NMHC contribution of diesel and gasoline to the atmosphere. Food cooking source profiles were also determined for chemical mass balance receptor model application. Initial source contribution estimates were carried out to determine the adequate combination of source profiles and fitting species. Ambient samples of NMHC were apportioned to motor vehicle exhaust, gasoline vapor, handling and distribution of liquefied petroleum gas (LP gas), asphalt operations, painting operations, landfills, and food cooking. Both gasoline and diesel motor vehicle exhaust were the major NMHC contributors for all sites and times, with a percentage of up to 75%. The average motor vehicle exhaust contributions increased during the day. In contrast, LP gas contribution was higher during the morning than in the afternoon. Apportionment for the most abundant individual NMHC showed that the vehicular source is the major contributor to acetylene, ethylene, pentanes, n-hexane, toluene, and xylenes, while handling and distribution of LP gas was the major source contributor to propane and butanes. Comparison between CMB estimates of NMHC and the emission inventory showed a good agreement for vehicles, handling and distribution of LP gas, and painting operations; nevertheless, emissions from diesel exhaust and asphalt operations showed differences, and the results suggest that these emissions could be underestimated.