Cold‐start and chemical characterization of emissions from mobile sources in Mexico

Abstract

In this work tailpipe and evaporative emissions from a set of normal and high emitter vehicle models, year 2006–2008 (low mileage) certified when new to meet the Tier 1 emission standard, were characterized for criteria pollutants (carbon monoxide, nitrogen oxides and hydrocarbons), and a suite of unregulated emissions including aliphatic and aromatic aldehydes, monocyclic aromatic compounds, 1,3 butadiene, n‐hexane and acrolein. Data were obtained under the three different driving conditions of the United States Federal Test Procedure, FTP‐75 cycle.

High emissions of both regulated and unregulated pollutants were observed in the cold‐start phase of the driving cycle for low mileage Tier 1 normal and high emitters engines. Data were compared with results obtained for a set of MY >1992–2005 that included vehicles with no catalytic converters, Tier 0 and MY 2000–5 Tier 1 emission standard with high mileage. The calculated average cold‐start emissions for normal emitters in grams are 0.93, 8.21 and 1.06 for NMHC CO, and NOx, respectively for Tier 1 low mileage vehicles. The reductions in emissions for Tier 1 normal emitters are 76%, 56% and 56% for NMHC, CO and NOx, respectively, but 58%, 30% and 25% for the high emitters. Differences in emission can be ascribed to the mileage accumulation more than technological improvements. Cold‐start emissions account in the USA roughly 10% of emissions from gasoline‐powered vehicles. In Mexico the fractions are likely to be higher because one must account also for the contribution of Tier 0 and the running exhausts emissions of vehicles with no catalytic converters.

Keywords:

• cold‐start extra emissions
• light duty gasoline vehicles
• ozone forming potential
• Mexico City
• FTP‐75