Ozone-forming potential of organic emissions from alternative-fueled vehicles

Abstract

Ozone-forming potentials of emissions from various alternative-fueled vehicles and gasoline-fueled vehicles have been evaluated using currently available data on the composition of organic emissions from such vehicles. Ozone-forming potentials are computed using three different methods: (1) a relative reactivity method; (2) an incremental reactivity method; and (3) a direct method using a photochemical trajectory model and detailed organic composition data for vehicular emissions. The three different methods give consistent results when the compositions of non-methane hydrocarbon (NMHC) emissions are similar. In those cases, the simplified relative reactivity or incremental reactivity methods are useful. However, when the compositions of NMHC emissions are not similar, a method which considers the detailed speciated organic emissions data, such as the direct method, is needed. More reliable, statistically significant data for organic composition of emissions from alternative-fueled vehicles as well as gasoline-fueled vehicles are needed to improve the estimates of ozone-forming potentials.