Hydrocarbon source apportionment for the 1996 Paso del Norte Ozone Study

Area of Science:

• Atmospheric Chemistry
• Air Quality Science
• Environmental Science

Background:

• High ozone concentrations pose a significant air quality challenge in the Paso del Norte region (El Paso, USA, and Ciudad Juárez, Mexico).
• Understanding the sources and processes contributing to ozone formation is crucial for effective mitigation strategies.

Purpose of the Study:

• To investigate the meteorological and air quality processes leading to elevated ozone levels in the Paso del Norte region.
• To identify and quantify the sources of non-methane hydrocarbons (NMHC) contributing to ozone formation.

Main Methods:

• Collected hourly air samples at urban and rural sites on both sides of the border.
• Utilized an automated gas chromatograph for detailed chemical analysis.
• Employed the Chemical Mass Balance (CMB) receptor model, integrating source profiles of various emissions (motor vehicles, fuels) to apportion NMHC.

Main Results:

• On-road vehicle emissions were identified as the dominant NMHC source, accounting for 50-67% in both cities, particularly during commute hours.
• Diesel exhaust contributed minimally (2-3% in Ciudad Juárez, <2% in El Paso).
• Liquid gasoline and vapor contributions increased throughout the day, mirroring motor vehicle exhaust patterns, suggesting significant tailpipe emissions.

Conclusions:

• Motor vehicle emissions, primarily from tailpipes, are the major contributors to NMHC in the Paso del Norte region.
• The findings provide critical data for developing targeted air pollution control strategies to reduce ozone levels.