Estimating Biogenic Contributions To Ozone Production At Continental Scale

Recent studies about urban plume pollution have highlighted the obvious role of strongly reactive biogenic hydrocarbons on secondary gaseous pollutants and aerosols formation. They have confirmed that looking for air pollution control strategies, these components have to be correctly considered. Photochemical processes modelling, which describes the relationships between primary compounds emissions and airborne concentrations, allows to realize these analyses. However, in current tools, the role of biogenic volatile organic compounds is often represented through a very simplified approach. The main purpose of this study is to analyse the sensitivity of biogenic VOCs modelling in the global process of secondary pollutants formation. A new chemical mechanism including a more realistic description (related to the state of the art) of biogenic processes has been developed in a continental scale model called CHIMERE. More precisely, new monoterpenes have been introduced in the primary pollutant classes, and some of the associated secondary products have been isolated. The new mechanism induces a significant effect on PAN and formaldehyde concentrations. Variations from 10% to 20% are observed. However, no important variations on ozone concentrations are noted. This fact points out difficulties encountered to assess objectively the performance of a photochemical model. If ozone concentrations are only considered, an unsuitable interpretation of the chemical regime could be given. Indeed this work is also oriented towards the determination of significant indicators of photochemical models quality. Transactions on Ecology and the Environment vol 66, © 2003 WIT Press, www.witpress.com, ISSN 1743-3541