Air quality effects of using reformulated and oxygenated gasoline fuel blends: application to the Strasbourg area (F)

The aim of this study is to evaluate the effects of the use of reformulated and oxygenated gasoline fuel blends on the air quality of an European city. The oxygenated compound added is the ethyl-t-butyl ether (ETBE). To perform this study, a numerical modeling approach has been chosen and the impacts of these fuel blends have been evaluated in terms of relative impacts on daily average concentrations and hourly maximum daily concentrations of air pollutants. The urban region of Strasbourg–Kehl in the middle of the upper Rhine valley has been chosen as area of investigation, due to (1) the existence of numerous previous studies on the meteorology and air quality of the region and (2) to the availability of emission inventories performed in the laboratory. The period of investigation, 11 May 1998, corresponds to a photochemical ozone pollution episode during which ozone concentrations exceeded the information threshold of the ozone directive of the European Union, i.e. 180 μg m−3 as 1 hourly average. The hourly emission inventories for the 9–15 May 1998 (kilometric resolution) for the Great Strasbourg–Kehl Area have been modified to build 12 emission scenarios with the help of recent available emissions factors for these reformulated and oxygenated fuel blends. The scenarios have been established by varying the fraction of gasoline passenger cars (from 30% to 100%) using three fuel blends. The mesoscale model EZM, including the updated chemical mechanism RACM, has been used to calculate the pollutants concentrations. Photochemical simulations reveal that all scenarios lead to an increase of NO concentrations (0.2–2.8% for the average concentrations over the whole domain) and to a significant decrease of the CO and VOCs levels (1.1–5.4% and 1.3–7.3%, respectively, over the whole domain) during the episode. There was no significant trend for the NO2 levels. For the ozone concentrations, the reductions appear to be modest (0.1–1.3% for the average concentrations over the whole domain).