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This study evaluates the influence of speciated emissions on ozone reactivity using the values of Maximum Incremental Reactivity published by the California Air Resources Board in September 1990. To evaluate the influence of fuels and vehicle specifications on speciated emissions and ozone reactivity, three different fuels (gasoline, reformulated gasoline, and methanol (M85)) were used. Hydrocarbon species were measured using three types of gas chromatographs. Aldehydes were collected in a dry cartridge and measured by High Performance Liquid Chromatograhpy (HPLC). Alcohols were collected using impingers and measured by a gas chromatograph. In the case of gasoline, as Non-methane Organic Gas (NMOG) is reduced, the proportion of speciated emissions with high ozone reactivity decreases, and this tends to lower Ozone Forming Potential (OFP). In the case of reformulated gasoline, OFP does not decrease, but Non-methane Hydrocarbons (NMHC) do as NMOG is reduced.

Hydrocarbons and other organic materials emitted from S.I. engines cause ozone to form in the air. Since each species of organic materials has a different reactivity, exhaust components affect ozone formation in different ways. The effects of exhaust emission control devices and fuel properties on speciated emissions and ozone formation were examined by measuring speciated emissions with a gas chromatograph and a high-performance liquid chromatograph. In the case of gasoline fuels, catalyst systems with higher conversion rates such as close-coupled catalyst systems are effective in reducing alkenes and aromatics which show high reactivities to ozone formation. With deterioration of the catalyst, non-methane organic gas (NMOG) emission increases, but the specific reactivity of ozone formation tends to decrease because of the increase in alkane contents having low MIR values.