Measurement of Emissions from Air Pollution Sources. 5. C₁−C₃₂Organic Compounds from Gasoline-Powered Motor Vehicles

TLDR

The study quantified tailpipe emissions of 66 volatile hydrocarbons, 96 semi‑volatile and particle‑phase organics, 27 carbonyls, and fine particle mass from a fleet of gasoline‑powered vehicles driven through a cold‑start FTP urban cycle using a two‑stage dilution sampling system and analytical methods on California Phase II Reformulated gasoline. The analysis identified six isoprenoids and two tricyclic terpanes as potential tracers, showed that n‑alkane and isoprenoid emissions from catalyst‑equipped vehicles mirror their gasoline composition while noncatalyst vehicles differ, and revealed that PAH distributions in gasoline differ markedly from those in tailpipe emissions, enabling direct comparison of semi‑volatile and particle‑phase organics between fuel and exhaust.

Abstract

Gas- and particle-phase organic compounds present in the tailpipe emissions from an in-use fleet of gasoline-powered automobiles and light-duty trucks were quantified using a two-stage dilution source sampling system. The vehicles were driven through the cold-start Federal Test Procedure (FTP) urban driving cycle on a transient dynamometer. Emission rates of 66 volatile hydrocarbons, 96 semi-volatile and particle-phase organic compounds, 27 carbonyls, and fine particle mass and chemical composition were quantified. Six isoprenoids and two tricyclic terpanes, which are quantified using new source sampling techniques for semi-volatile organic compounds, have been identified as potential tracers for gasoline-powered motor vehicle emissions. A composite of the commercially distributed California Phase II Reformulated Gasoline used in these tests was analyzed by several analytical methods to quantify the gasoline composition, including some organic compounds that are found in the atmosphere as semi-volatile and particle-phase organic compounds. These results allow a direct comparison of the semi-volatile and particle-phase organic compound emissions from gasoline-powered motor vehicles to the gasoline burned by these vehicles. The distribution of n-alkanes and isoprenoids emitted from the catalyst-equipped gasoline-powered vehicles is the same as the distribution of these compounds found in the gasoline used, whereas the distribution of these compounds in the emissions from the noncatalyst vehicles is very different from the distribution in the fuel. In contrast, the distribution of the polycyclic aromatic hydrocarbons and their methylated homologues in the gasoline is significantly different from the distribution of the PAH in the tailpipe emissions from both types of vehicles.